MARSBUGS: The Electronic Astrobiology Newsletter Volume 9, Number 33, 9 September 2002. Editor/Publisher: David J. Thomas, Ph.D., Science Division, Lyon College, Batesville, AR 72503-2317, USA. dthomas@lyon.edu Contributing Editor: Julian A. Hiscox, Ph.D., School of Animal and Microbial Sciences, University of Reading, Reading, RG6 6AJ, United Kingdom. J.A.Hiscox@reading.ac.uk Marsbugs is published on a weekly to monthly basis as warranted by the number of articles and announcements. Copyright of this compilation exists with the editors, except for specific articles, in which instance copyright exists with the author/authors. While we cannot effectively copyright our mailing list, our readers would appreciate it if others would not send unsolicited e-mail using the Marsbugs mailing list. The editors do not condone "spamming" of our subscribers. Persons who have information that may be of interest to subscribers of Marsbugs should send that information to the editors. E-mail subscriptions are free, and may be obtained by contacting either of the editors. Information concerning the scope of this newsletter, subscription formats and availability of back-issues is available from the Marsbugs web page at http://welcome.to/marsbugs or http://www.lyon.edu/webdata/users/dthomas/marsbugs/. _____________________________________________________________________ CONTENTS 1) EXTREME ANIMALS By Leslie Mullen 2) EARTH SUFFERED PULSES OF MISERY IN GLOBAL WILDFIRES 65 MILLION YEARS AGO By Lori Stiles 3) NO PLACE FOR LIFE TO HIDE FROM MARS EXPRESS From ESA Science News 4) SPACE POWER By Linda Voss 5) TUNING IN TO OTHER WORLDS By Leslie Mullen 6) DIAMONDS REVEAL EARLY WATER WORLD OF EARTH By Robert Roy Britt 7) MUDDY WATERS By Patrick L. Barry 8) RUNNEGAR TO LEAD NASA ASTROBIOLOGY INSTITUTE NASA/ARC release 02-100AR 9) HOUSTON, ARE WE THERE YET? By Trudy E. Bell 10) MARS EXPLORER ROVER 2003 LANDING SITES From Astrobiology Magazine 11) NEW ADDITIONS TO THE ASTROBIOLOGY INDEX By David J. Thomas 12) CASSINI SIGNIFICANT EVENTS NASA/JPL release 13) INTERNATIONAL SPACE STATION SCIENCE OPERATIONS STATUS REPORT NASA/MSFC release 02-216 14) MARS ODYSSEY THEMIS IMAGES NASA/JPL/ASU release 15) STARDUST STATUS REPORT NASA/JPL release _____________________________________________________________________ EXTREME ANIMALS By Leslie Mullen From Astrobiology Magazine 2 September 2002 All life on Earth is based on water. The water in our cells constantly needs to be replenished, and if water is not available, we could die. Some organisms, however, have evolved to adapt to a loss of water-in essence, to cheat death until water reappears. One such organism is a microscopic animal called a "tardigrade." J. A. E. Goeze, who published the first paper on tardigrades in 1773, said, "Strange is this animal... because it resembles a bear in miniature." Because of this description, and because tardigrades normally live in water, they are also known as "water bears." Tardigrades look more like a candy Gummy Bear than a grizzly bear- they have the bright orange, red or green colors of Gummy Bears, and a gummy surface texture. Their inflated round bodies have four pairs of stubby little legs. They use these clawed limbs to walk, grasping onto lichen or moss as they amble along. If their environment dries up, the tardigrades undergo a process called anhydrobiosis (life without water). A sugar called trehalose moves into their cells to replace the lost water, and the tardigrade curls into a little ball called a "tun." Their metabolism lowers to a death-like 0.01% of normal, or is entirely undetectable. Depending on how long they have been in an anhydrobiotic state, tardigrades can become active again within a few minutes to a few hours after exposure to water. Anhydrobiosis is just one type of a range of adaptable techniques called cryptobiosis. The other types of cryptobiosis are cryobiosis (cold temperatures), osmobiosis (salt water), and anoxybiosis (reduction of oxygen). Cryptobiotic animals were first documented in 1702 by Anton van Leeuwenhoek, when he observed tiny life forms in sediment collected from rooftops. He dried the "animalcules" to preserve them, and when he later added water he saw the creatures begin to move around. (The animals van Leeuwenhoek studied were probably rotifers-a microscopic organism that uses a wheel-like organ to swim and feed). Because of their ability to withstand hostile conditions, tardigrades and other cryptobiotic organisms are of interest to astrobiologists. Some tardigrades can survive in temperatures as low as minus 200 degrees Celsius (minus 328 F). Others can survive temperatures as high as 151 degrees C (304 F). Tardigrades can survive the process of freezing or thawing, as well as changes in salinity, extreme vacuum pressure conditions, and a lack of oxygen. Tardigrades also are resistant to levels of X-ray radiation that are hundreds of times more lethal to humans and other organisms. This resilience stems from the tardigrade's ability to survive without water. While the water in our cells is necessary for our survival, it also makes us extremely vulnerable. Whatever affects water also affects the cells of our bodies. When tardigrades are in a state of anhydrobiosis-when their cells contain no water-they become resistant to many of the things that normally would be fatal to water-based creatures. "When tardigrades dry up into the little barrel called a tun, they become amazingly resistant to just about everything," says Jim Garey, an evolutionary biologist at the University of South Florida. "Tardigrades can survive such extreme conditions for long periods of time. Live tardigrades have been regenerated from dried-up mosses more than 100 years after they were collected." There are other creatures on Earth, called "extremophiles," that are able to live in extreme environmental conditions. Extremophiles can live in boiling hot, extreme cold, salty, and dry conditions in short, all the conditions that tardigrades can survive. Tardigrades, however, are not extremophiles. "Tardigrades are not true extremophiles because they are not adapted to live in extreme conditions," says Garey. "They can merely survive exposure to such conditions. The longer they undergo such exposure, the greater their chance of dying. Tardigrades are always waiting for something better." Tardigrades, rotifers, nematodes and other microscopic cryptobiotics were intensively documented during the eighteenth century. Since then, however, interest in these tiny creatures has waned. One problem with studying tardigrades today, says Garey, is that some of the information about these creatures is over 100 years old-collected long before the advent of modern scientific techniques and instruments. So far, about one thousand tardigrade species have been documented, but that number may be misleading. Some tardigrade species may have been "discovered" more than once by different sources. Some species may have been lumped into more common categories because of the poor descriptions typical of earlier studies. "Most of us who describe new species recognize that--since there is no international database yet--we can't be sure of the count," says William Miller, a biologist at Chestnut Hill College in Philadelphia. "The taxonomy of tardigrades is continuing to evolve. As we become more detailed, we are discovering more differences. As we explore new places on the Earth, we discover more new species." Although their most typical home is the thin film of water that coats mosses and lichens, tardigrades have been found in a vast range of habitats--in marine, fresh water, and semi-aquatic terrestrial environments ranging from tropical rainforests to the Arctic Ocean. Scientists have reported finding tardigrades in hot springs, on top of the Himalayas, and under a 5 meter layer of solid ice. It is thought that tardigrades are widely distributed because they are carried on the wind, still clinging to their little bits of dried moss. This theory seems to be supported by the discovery of tardigrades on remote volcanic islands, where they could only have been deposited by wind or birds. Garey believes that the tardigrade's preference for mosses and lichen is due to the wet/dry cycles these plants undergo. In areas that don't experience wet/dry cycles, tardigrades tend to be out-competed by other animals like nematodes. But nematodes are not as good at surviving without water as are tardigrades. "In mosses and lichen, with their wet and dry cycles, tardigrades have found their ecological niche," says Garey. "While other organisms like nematodes and rotifers can also undergo anhydrobiosis, tardigrades are the most efficient at the process--they do it best." Like other animals, the ancestors of tardigrades probably first appeared during the Cambrian explosion, 540 million years ago. Tardigrades share a common ancestor with arthropods, nematodes, and onychophorans ("velvet worms"), because these animals all grow by molting (shedding their cuticle outer layer). These molting animals are classed together under the name Ecdysozoa. Arthropods are a hugely diverse group of organisms they include such different animals as centipedes, lobsters, and fruit flies--but they all have jointed appendages and a hard exoskeleton. Like arthropods, tardigrades have leg-like appendages that they use to move around-- but unlike arthropods, tardigrade appendages are unjointed. Tardigrades and nematodes both have a spear-like mouth part called a "stylet" that they use to pierce their prey and suck their juices as though through a straw. But tardigrades have two stylets, while nematodes only have one (arthropods, meanwhile, have jaws). Tardigrades are thought to be the most closely related to onychophorans, caterpillar-like invertebrates that share traits with both arthropods and annelids (worms). Both tardigrades and onychophorans have unjointed appendages that terminate in claws. But tardigrades lack the antennae, jaws, and respiratory system of the onychoporans. While tardigrades have been classified as nematodes, arthropods or onychophorans in the past, today tardigrades have their own separate phylum, Tardigrada. Scientists aren't sure exactly when the tardigrade phylum first emerged. For one thing, there aren't many tardigrade fossils. "A few examples of tardigrades that look just as they do today have been discovered encased in cretaceous amber," says Miller. "That would place them at about 100 million years old in their present form. Few other records exist because of their small size and soft bodies; they do not fossilize well and are even more difficult to see." Garey is studying the DNA of tardigrades to pin down where they belong in the evolutionary diagram called the Tree of Life. An organism's position in the Tree can indicate when they appeared in the course of evolutionary history. But placing a precise date on their emergence has proved to be difficult. "It's hard to really date the emergence of tardigrades, nematodes, and other such animals," says Garey. "Nematodes, for instance, have faster evolution rates than other animals. Also, dating based on nucleotide substitutions so-called molecular clock' dating results in dates ranging as far as 700 million to 1.5 billion years ago." By studying tardigrade DNA, Garey and his team also hope to figure out how all the different tardigrade species are related to each other. "The tardigrades most likely originally evolved in the ocean, and only later colonized fresh water and terrestrial habitats," says Garey. "One group of tardigrades-the Heterotardigrada-is mostly marine but has some terrestrial members. The other group of tardigrades--the Eutardigrada--is exclusively terrestrial. An interesting question is whether the eutardigrades evolved from the terrestrial heterotardigrades or whether terrestrial tardigrades evolved twice." The ability of terrestrial tardigrades to undergo cryptobiosis has led some to suggest that they could be transferred by panspermia-- that is, between different planets via meteorites. Although he finds the concept highly unlikely, Garey says, "If you had to pick an animal candidate, I'd pick a tardigrade." Perhaps future research will lend some credibility to this idea. Miller is mentoring a group of students in the NASA Student Involvement Program, and they have proposed a project to fly tardigrades on the space shuttle. This project could determine how tardigrades are affected by low gravity and test whether tardigrades can survive in space. What next? The dispersion of tardigrades is not well understood, and demands closer study. For instance, tardigrades seem to be more common in temperate and polar regions than in the tropics, but no one knows why. And some habitats that would seem to suit tardigrades perfectly are found not to support any tardigrade populations. "In the wild, populations of tardigrades are patchy," says Garey. "You might find one area that is rich in tardigrades, while another nearby is completely barren. We don't know why, so more research needs to be done in this area." Because most of the research on tardigrades has been done in Europe, tardigrade populations in South America, Australia, Asia, Africa, and North America are not as well documented. The same is true for the oceans: marine tardigrades have a higher diversity, and therefore may have more species, than tardigrades on land, but so far the marine environment is mostly unexplored. "We know of 140 marine tardigrade species, but there are probably thousands more," says Garey. To study the ecology of tardigrades in the wild, you first have to find them. Their small size makes identifying and collecting tardigrades a challenge, but Garey and his team are developing methods to extract DNA from the sediment in which the microscopic animals live. Miller, meanwhile, is working on the description of several new species of tardigrades, and has a number of canopy, ecological, diversity, and taxonomic projects under way. He also is working on National Science Foundation grant proposals to study the tardigrades of China, Australia, and North America. Additional information on this article is available at http://www.astrobio.net/news/article261.html. _____________________________________________________________________ EARTH SUFFERED PULSES OF MISERY IN GLOBAL WILDFIRES 65 MILLION YEARS AGO By Lori Stiles University of Arizona release 3 September 2002 Global wildfires ignited by high-velocity debris from the catastrophic impact of an asteroid or comet with Earth 65 million years ago spread over southern North America, the Indian subcontinent and most of the equatorial part of the world one to three days after impact, according to a new study. But northern Asia, Europe, Antarctica and possibly much of Australia may have been spared, David A. Kring of the University of Arizona and Daniel D. Durda of the Southwest Research Institute report in the Journal of Geophysical Research ­ Planets. UA planetary scientist H. Jay Melosh in 1990 and others modeled global wildfire scenarios from the horrific impact that is thought to have led to one of the greatest mass extinctions in Earth history, including dinosaur extinction. The impact that blasted the immense Chicxulub crater near Yucatan, Mexico, marked the end of the Age of Reptiles, the Mesozoic, and heralded the Age of Mammals, the Cenozoic. "We've added more detail in re-evaluating the extent of the wildfires," Kring said. "Our new calculations show that the fires were not ignited in a single pulse, but in multiple pulses at different times around the world. We also explored how the trajectory of the impacting object, which is still unknown, may affect the distribution of these fires." Their more detailed modeling suggests pulses of misery for life on Earth during days after impact. More than 75 percent of the planet's plant and animal species did not survive to see the Cenozoic. "The fires were generated after debris ejected from the crater was lofted far above the Earth's atmosphere and then rained back down over a period of about four days. Like countless trillions of meteors, the debris heated the atmosphere and surface temperatures so intensely that ground vegetation spontaneously ignited." The collision was so energetic--10 billion times more energetic than the nuclear bombs that flattened Hiroshima and Nagasaki in 1945--that 12 percent of the impact debris was launched beyond Earth into the solar system, Kring said. About 25 percent of the debris rained back through the atmosphere within two hours of impact. Fifty-five percent fell back to Earth within 8 hours of impact, and 85 percent showered down within 72 hours of impact, according to Kring's and Durda's calculations. Both physics and Earth's rotation determined the global wildfire pattern. High-energy debris would have concentrated both around the Chicxulub crater in Mexico and its global antipode--which corresponded to India and the Indian Ocean 65 million years ago. "The way to think of this is, the material was launched around Earth and headed on a return trajectory to its launch point," he explained. "Then, because the Earth rotates, it turned beneath this returning plume of debris, and the fires migrated to the west. That's what causes the wildfire pattern." Durda has turned the simulations into a movie that can be viewed at the Lunar and Planetary Lab Space Imagery Center Web site, http://www.lpl.Arizona.edu/SIC/news/chicxulub2.html Kring and Durda noted not in this paper, but in an unrefereed abstract, that post-impact wildfires generated as much carbon dioxide, and perhaps more carbon dioxide, than limestone vaporized at the impact site. Wildfires played at least as big a role as the limestone target site in disrupting the carbon cycle and in greenhouse warming. The team proposes to model other impact events using the code they developed for these simulations. Contact: David A. Kring Phone: 520-621-2024 E-mail: kring@lpl.arizona.edu Daniel D. Durda Phone: 303-546-9670 E-mail: durda@boulder.swri.edu Lori Stiles UA News Services Phone: 520-621-1877 The Chicxulub wildfire movie is on the web at http://www.lpl.arizona.edu/SIC/news/chicxulub2.html. The original press release is available at http://ali.opi.arizona.edu/cgi- bin/WebObjects/UANews.woa/1/wa/SRStoryDetails?ArticleID=5767&wosid=G1 Qx2jcSGUlM5fXNis6GWw. _____________________________________________________________________ NO PLACE FOR LIFE TO HIDE FROM MARS EXPRESS From ESA Science News http://sci.esa.int 3 September 2002 Of all missions sent to Mars only one, the Viking 26 years ago, has dared to search for life. Its only conclusive result was that finding proof of extraterrestrial life proved to be much harder than expected. Second attempts never followed, until now. ESA's Mars Express, the next mission to the Red Planet and the first European one, has an ambitious goal. To be launched in 2003, Mars Express will be the first spacecraft after Viking to search for direct and indirect evidence for past or present life on Mars. This time, scientists are equipped with more knowledge and insight in how to detect martian life. The chances of success look very good. The expectations regarding life on Mars have changed substantially since the Viking missions. Today's scientists are considering several alternatives: 1. Martian life exists, but the life forms are so small you can barely see them and they probably live underground. 2. Martian life is not only small but also dead and extinct by now, so the search is for fossils and not for living organisms. 3. There is no life on Mars now and there never has been. Each of the two Viking landers, launched in 1976, carried three biological experiments. All of them searched for microbes or microorganisms, or their "signature", in soil samples. All three experiments, based on different concepts, quickly produced positive results. The thrill died down as scientists soon realized that a non-biological process could easily explain most of the results. Surprisingly, the non-biological process that had tricked scientists had not been anticipated by anyone prior to the launch. ESA's Mars Express will arrive at Mars in December 2003 and will follow a strategy quite different from that of the Viking. It consists of an orbiter plus a lander, called Beagle 2, "as an homage to the ship on which Charles Darwin found the inspiration to write his theory of evolution," says Agustin Chicarro, ESA Project Scientist for Mars Express, also pointing out that "indeed this mission could be as revolutionary as Darwin's ideas because it is the first one after the Viking to search for life." A key difference between Mars Express and the Vikings is that now scientists are aware that they should also look for past, fossilized life. A few biological experiments are not enough. Mars Express's scientists will combine many different types of test findings, for example, to help discard contradictory results. Some of the evidence will be indirect, mostly focused on the search for water. The Mars Express orbiter will have seven instruments on- board, apart from the lander Beagle 2. One of these instruments will image the entire planet in full color, in 3-D, at a resolution of about 10 meters. Another will map the mineral composition of the surface with great accuracy. "These data will be key to determine how much water there was in the past, and from that you can estimate how much water there is left," says Chicarro. A third instrument on-board the Mars Express orbiter will search for water below the surface, to measure the thickness of the layer of ice or permafrost, that is, a thick subsurface layer of soil that has a temperature below 0 C all year round. Other studies will determine the amount of water in the atmosphere and the water cycle: how the water is deposited in the poles and how it evaporates depending on the seasons. The search for direct evidence of past or present biological activity will be the task of the lander, Beagle 2. Once deployed, in an area that was probably flooded in the past, Beagle 2 will unfold its robotic arm where most of the instruments are located. Beagle 2 carries several instruments, among them a gas analysis package that will determine whether carbonate minerals on Mars, if they exist, have been involved in biological processes. If there are certain gases on Mars, such as methane, that scientists believe can only be produced by organisms living either on the surface or below it, Beagle's 'nose' will detect them. The feeble martian atmosphere cannot prevent ultraviolet radiation from the Sun killing potential life. For this reason, it is important to get samples from places below the surface, under large boulders, and within the interiors of rocks. Beagle 2 will collect samples with a mole able to crawl short distances across the surface, about 1 centimeter every six seconds, and to dig down to 1.5 meters deep. If the digging proves to be hard, a grinder will help access the rocks' protected interior. With all these available tools, Mars Express will be the best mission ever to discover life on Mars. There can be no place for life to hide from it. More about Mars Express http://sci.esa.int/marsexpress Chances of life are linked to water http://spdext.estec.esa.nl/content/doc/90/30352_.htm Image 1 [http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12 &oid=30347&ooid=30348] D. radiodurans, a so-called extremophile, here on Earth. Microscopically small, it withstands attacks from acid baths, high and low temperatures, and even radiation. It would probably resist Mars's highly oxidative environment also. Copyright (c) Michael J. Daly, Uniformed Services University of the Health Services. Image 2 [http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12 &oid=30347&ooid=26723] Mars Express in orbit around Mars. Image 3 [http://sci.esa.int/content/searchimage/searchresult.cfm?aid=9&cid=12 &oid=30347&ooid=28279] The Beagle 2 lander, to be carried on ESA's Mars Express, is equipped with a suite of instruments designed to look for evidence of life on Mars. An additional article on this subject is available at http://www.spaceflightnow.com/news/n0209/07marslife/. _____________________________________________________________________ SPACE POWER By Linda Voss From NASA Science News 3 September 2002 Scientists ponder the question, "What advances in power technology are required to send human and robotic explorers throughout the solar system?" Beyond all the planets in our solar system in a cold, dark, empty region of space, Voyager 1 continues its 25-year journey of exploration. It's headed for the heliopause, that boundary where the Sun's influence ends and the dark recesses of interstellar space begin. From where Voyager sits, the Sun is merely the brightest star in the sky--seven thousand times dimmer than we see it from Earth. Voyager doesn't have any solar panels; they wouldn't do any good so far from the Sun. The probe stays in touch by carrying its own power source, an early radioisotope thermoelectric generator (RTG), which converts the heat generated from the natural decay of its radioactive fuel into electricity. Its RTG will supply Voyager with electricity at least until 2020. Space probes that travel much beyond Mars need more power than solar cells can provide. Another example is the Ulysses spacecraft. It was launched in October 1990 from the space shuttle on a mission to study the Sun's poles. To get above the Sun, Ulysses had to fly around Jupiter and slingshot out of the plane of the planets. Near Jupiter, the Sun's rays are 25 times weaker than near Earth. Solar panels large enough to catch this weak energy would have weighed 1,200 pounds, doubling the weight of the spacecraft and making it too heavy for booster rockets from the shuttle. Instead, Ulysses was equipped with an RTG weighing only 124 pounds. It easily powers all the probe's onboard systems, including navigation, communication and scientific instruments. A probe like Ulysses needs a couple hundred watts of power to operate onboard systems. For comparison, the shuttle's onboard systems use 5 to 10 kilowatts (kW) of power, 50 times that. The International Space Station (ISS) uses 10 times more, or about 100 kW for onboard systems. The ISS never leaves Earth orbit, which reduces the power it needs. Human missions beyond Earth's neighborhood, however, will require power not only for onboard systems, but also for propulsion and for systems to support humans when they arrive wherever they're going. "To pursue ambitious human missions across the solar system, perhaps returning to the Moon, perhaps going on to Mars, will require hundreds to a thousand kilowatts on the surface and hundreds to thousands of kilowatts for transportation systems," says John Mankins, chief technologist for the Advance Systems Program at NASA headquarters. You can't just plug into the nearest electrical outlet, he added. You have to bring your own power source. Ideally, you'd like to find something that could provide power for both propulsion and operations. Since Robert Goddard's first test launch of a rocket in 1916, space missions have used chemicals to get the acceleration needed to escape Earth's gravity. A rocket's 5- to 15-minute burn sends the spacecraft towards its destination; then it coasts the rest of the way unless it uses the gravity of other planets for an additional boost. For Voyager, it took years to reach Saturn and then the spacecraft was only able to spend days in the Saturn system and only hours near the planet itself. Mission planners would like to do better in the future. From the perspective of the Exploration Office at the Johnson Space Center, Jeff George sees "an evolving family of related power and propulsion technologies" for the next wave of human exploration. The first likely candidate is electric propulsion (EP). You don't need as much thrust in space as you do to escape Earth's gravity, explains George, but you do need to produce thrust using very little fuel because of weight restrictions. Electric propulsion could provide fuel- efficient thrust after an initial chemical boost into space. Specific impulse--that is, the pounds of thrust produced per pound of propellant used per second--is a measure of the efficiency with which a system uses fuel to produce thrust. Higher is better. The space shuttle, which stays near Earth, uses chemical propulsion with a specific impulse of 450 seconds or 450 pounds of thrust for a pound of propellant per second. EP has 10 times the specific impulse of chemical propulsion and potentially can go as high as 10,000 seconds. EP got its first try in 1998 on Deep Space 1--a spacecraft that tested many new technologies before it flew by comet Borrelly in 2001. Deep Space 1 needed 2.5 kW to power both its electric ion propulsion drive and other onboard systems. The energy came from an innovative collector consisting of advanced solar cells and a lens to concentrate sunlight on the panels. Together they achieved a 23% efficiency in converting sunlight to electricity compared with 14% efficiency for the solar arrays on the ISS. Building on the success of Deep Space 1, a new mission named "Dawn" will leave Earth in 2006. Propelled by an ion engine with a specific impulse of 3100 seconds, Dawn will travel to Ceres and Vesta, two of the biggest asteroids in the solar system. Although Ceres and Vesta lie farther from the Sun than Mars does, the spacecraft will be able to draw all the power it needs from 7.5 kW solar arrays. Manned missions need more power. "The next step for a [human-crewed] Mars mission," says Jeff George, "is to step up to 5-10 megawatts of nuclear power and then scale up the electric thrusters to megawatts per engine." Going from kilowatts to megawatts is not a simple problem. NASA is now working on a 5-10 kW next-generation ion propulsion system. George envisions small, nuclear-electric vehicles of 100-200 kW exploring the outer planets as a pilot version of the megawatt scale they'd like to use for human exploration. To run a megawatt EP system, you need a source with both high energy and high power. As John Cole, manager of the Revolutionary Propulsion Research Project Office explained, "Energy is the most important factor, but power (the energy released per unit time) determines acceleration." So what source provides enough power? "Nuclear has plenty of energy--and potentially plenty of power, too," Cole observes. "Solar panels provide insufficient power for the entire vehicle to accelerate to levels that permit short trip times." Radioisotope power sources (like the RTGs onboard Voyager) give off a lot of energy over a long period of time, but not a lot of power, only tens to hundreds of watts. To get kilowatts to megawatts of power, you have to go to nuclear fission, says Les Johnson, of NASA's Advanced Space Transportation Program. Fission, in which a neutron splits an atom into two radioactive isotopes, is the process nuclear power plants on Earth use to produce electricity. "Bringing along a fission reactor on a spacecraft would be like bringing along your own [mini] power plant," says Johnson. A fission reactor is capable of fueling high-performance electric propulsion beyond the inner solar system. It is longer duration and power rich for performing sophisticated scientific investigations, high-data rate communications, and complex spacecraft operations. That's a pretty good resume for fission, but it still doesn't pass John Cole's test. Cole set himself the requirement of getting humans to the outer planets in a year and back in a year. Nuclear fission has enough energy, but not enough power to provide the acceleration needed. NASA is designing a 300-kW flight configuration system using nuclear fission. But to meet Cole's test, "one needs a very high specific power, power per unit mass vehicle three orders of magnitude better than what we've currently planned for nuclear fission." For that, you have to step up to nuclear fusion--the same process that powers the Sun and stars. Fusion, which releases energy by combining rather than splitting atoms, could in principle supply gigawatts of clean power. However, fusion propulsion systems as we understand them today would be very big, requiring a vehicle the size of the space station or Battlestar Galactica, weighing hundreds of tons--although the size might come down with research. Fusion engines would be very efficient fuel burners with a specific impulse of 100,000 seconds. "Though we couldn't do it in 10 years, if we could launch a fusion propulsion system 10 years from now, we could send a vehicle out to catch Voyager and bring it back," says Cole. That kind of power and speed shortens the time that astronauts would be exposed to harmful cosmic radiation and the bone loss that comes from prolonged weightlessness. Perhaps there's something even better than fusion: A thruster powered by matter-antimatter annihilation would have a specific impulse of 2,000,000 seconds, according to Cole. It sounds like science fiction, but researchers are learning to create and store small amounts of antimatter in real-life labs. A portable electromagnetic antimatter trap at Penn State University, for example, can hold 10 billion antiprotons. If we could learn how to use such antimatter safely, we could impinge some on a thin stream of hydrogen gas to create thrust. Alternatively, a little antimatter could be injected into a fusion reactor to lower the temperatures needed to trigger a fusion reaction. "Propulsion isn't the only reason to go nuclear," notes Colleen Hartman, director of solar-system exploration at NASA headquarters. "Onboard systems benefit, too. The excess power is like getting the Las Vegas strip instead of a single light bulb. It gives you greater communication and mission flexibility." The Mars Smart Lander and Mobile Laboratory, slated for launch as early as 2009, will be upgrading from solar to nuclear power: "Putting nuclear power on board will extend the mission from 3-6 months [with solar power] to 5 years [with radioisotope power]," says Ed Weiler, head of the Space Science Enterprise at NASA headquarters. "It will enable the rover to drive to a location rather than having to land there. The bandwidth for data communication goes way up, and the rover can work 24 hours a day. Everything increases by a factor of 10 when you add an RTG to a mission." Scaling up from the Mars Lander to a human mission on Mars requires more power--about 30 kW to heat and cool a human habitat, run computers and lights, make oxygen, recycle water and recharge the rovers, says Jeff George. For a long mission "we don't have the kind of energetics where you can dash back home [in case of trouble]," adds Gary Martin, assistant associate administrator for Advanced Systems in NASA's Office of Space Flight. "You're building things that have to be ultra reliable, self-healing, and autonomously sense when they're hurt." Broken parts will have to be made or repaired on site: you can't bring spare parts. Power-intensive processes like making parts or producing propellant for leaving Mars would be another 60 kW, according to George. In the end, one power source does not fit all needs. Looking at the big picture, John Mankins says "we need very high-efficiency, high- power electric propulsion for interplanetary travel; we need reliable and affordable high-energy chemical propulsion systems for going up and down from planetary surfaces; and we need to be able to store chemical or solar power in order to live and work on the surface. Robots could use radioisotope power; and there's reactor power and wireless beaming to consider as well." The choices are many, yet one thing is clear. Wherever we go in space and whatever we do there, we'll need more power. Additional information on this article is available at http://science.nasa.gov/headlines/y2002/03sept_spacepower.htm?list522 60. _____________________________________________________________________ TUNING IN TO OTHER WORLDS By Leslie Mullen From Astrobiology Magazine 4 September 2002 As the Aurora Borealis illuminates the night with sheets of shimmering color, the phenomenon seems silent, almost stealthy. The Aurora isn't silent, however. There is a radio counterpart that sings a tune for the lights to dance to. It's not a song we could hear without a radio receiver, of course. And the electromagnetic radio waves are sent out into space rather than down towards the ground. The radio waves are generated by the Earth's magnetosphere, an invisible system of magnetic fields, electric currents and charged particles that surrounds the Earth. Sub-atomic particles from the Sun--called "solar wind"--continually hit the Earth's magnetosphere and create a build-up of energy. Under certain conditions, this stored energy combines with direct energy from the solar wind, energizing electrons and ions inside the magnetosphere. Auroras, or "Northern Lights," are created when some of these energized particles fall onto the atmosphere at high latitudes, generating colored light when they interact with gases. Energy from other particles turns into the low frequency radio waves. Other planets in our solar system with magnetospheres--Jupiter, Saturn, Uranus and Neptune--also experience visual light Auroras and the related radio emissions. Some scientists think it may be possible to detect planets beyond our solar system by looking for similar radio signals. A team of scientists working on a radio telescope called the Low Frequency Array (LOFAR) plan to do just that. LOFAR is a joint project of the Naval Research Laboratory (NRL), MIT's Haystack Observatory, and the Netherlands Foundation for Research in Astronomy. LOFAR is still in the planning stages--the array will not be operational until 2006 or later--but scientists from the NRL, NASA's Goddard Space Flight Center, the National Radio Astronomy Organization, and the Observatoire de Paris have been testing the feasibility of radio planet detection by using the Very Large Array (VLA) in New Mexico. The VLA was never designed to detect frequencies below 100 megahertz (MHz), but the scientists have been able to push detection levels down to 74 MHz. "A highly magnetized planet could have emissions at frequencies such as 74 MHz," says Robert Mutel, professor of astronomy at the University of Iowa. "Below this frequency, it is extremely difficult to conduct sensitive array observations." But if radio emissions from extrasolar planets are anything like those of our own solar system, the scientists will have to look for much lower frequencies. The Aurora-related radio emissions from Earth, Saturn, Uranus and Neptune are all below 1 MHz. Such bursts from Jupiter occur at frequencies up to 40 MHz. The strength of a planet's magnetic field determines the frequencies of the radio bursts, and, except for the Sun, Jupiter has the strongest magnetic field in our solar system. Problem #1: the ionosphere The upper region of the Earth's atmosphere, called the "ionosphere," creates a problem when trying to detect very low frequency signals. The density of electrons in this region turns it into a sort of mirror, causing radio signals below 3 MHz to bounce back into space. Incoming radio waves that are below this ionosphere cut-off never reach the ground, and so can't be observed by ground-based radio telescopes. Even signals that are above this cut-off experience some degradation as they pass through the ionosphere. Tom Carr, an astronomer who studies low frequency radio emissions at the University of Florida's Radio Observatory, says that although much of Jupiter's radio emissions are above the ionosphere cut-off, the signals still can be difficult to detect. Jupiter is, relatively speaking, right next door, so an extrasolar planet many light years away might be even harder to detect. Given that only one planet in our solar system emits frequencies above the ionosphere cut-off, what are the odds of finding higher frequency signals from extrasolar planets? "The current generation of models predict that a small number of extrasolar planets may have emissions above the ionosphere cut-off," says Joseph Lazio of the Naval Research Laboratory, one of the participants of the VLA planet search. However, "no radio emission from an extrasolar planet has been detected yet." The LOFAR team has suggested that because many of the known extra- solar planets are much more massive than Jupiter, they also may have larger magnetic fields. This could result in a much larger signal. In addition, many of these planets are very close to their host stars--some with orbits lasting only a few days. Being so close to their stars, these plants probably undergo intense exposure to solar wind. The intensity of the solar wind may serve to increase the power of planetary radio signals. Problem #2: planetary characteristics In our solar system, a planet's mass, magnetism, and proximity to a star all factor into the strength of a radio signal. For instance, the Earth, although less massive than Uranus and Neptune, has a brighter radio emission due to its closer orbit around the Sun. In addition, a planet's spin rate can influence the radio signal, as can the presence of moons. Jupiter's radio emission, for instance, is driven by the orbital energy of the innermost moon Io. Jupiter's rotational energy and energy storage in the magnetosphere also affect the strength of its radio signal. We don't know if these factors hold true for planets outside our solar system, however. Lazio notes that many of the extrasolar planets may be tidally locked to their stars. This means the planets would have a slow spin rate, and therefore may have a weak magnetic field and a weak radio signal. We don't even know if extrasolar planets have magnetospheres--they may instead be non-magnetized bodies like Mars or Venus. Or they could be like Mercury, a planet with a weak magnetosphere and no significant atmosphere. Auroral activity requires an ionized upper atmosphere, so Mercury doesn't emit Aurora-related radio. Dennis Gallagher, a plasma physicist at NASA's Marshall Space and Rocket Center, says that older planetary systems, where the electromagnetic dynamo responsible for planetary magnetic fields has slowed down, may be less likely to have Aurora-related radio bursts. He suggests that younger planetary systems will be the most promising sources of radio bursts. "It would seem likely that any relatively young system will have planets with either liquid cores or gas giants with fluid cores," says Gallagher. "It's hard to imagine a planet forming without rotation, and the combination appears likely to create a magnetic field. If you have a magnetic field and active sun, then you just about have to have radio emissions." According to Gallagher, our ability to detect will be influenced by how the signal is sent out into space. The radio bursts are composed of accelerated beams of energized particles, and it would be easier for us to find the beams when they are directed towards Earth. "Some emissions are both strong and directed," says Gallagher. "Any directed beaming would increase the signal strength when the signal passes the Earth." Problem #3: solar radio Stars also emit low frequency radio waves. Our Sun, for instance, emits various frequencies often in the same range as Jupiter, depending on the amount of solar activity. As radio astronomers point their telescopes to tiny pinpricks of starlight, how will they be able to discriminate between planetary and stellar radio frequencies? Because Aurora radio bursts are dependent on the Sun-planet relationship, planetary radio bursts may be coordinated with the planet's orbit around its star. This would give the planets a signature radio signal that is quite different from the typically sporadic radio bursts of a star. Problem #4: noise The constant galactic background radiation adds another complication to radio planet searches. In addition, terrestrial radio interference at low frequencies is an increasingly serious problem for radio astronomers. This huge amount of radio noise that we generate on Earth will make things difficult for LOFAR. "The concept of searching for magnetospheric planets this way has been looked at before," says Gallagher. "There was a proposal once to locate a Very Long Baseline Interferometer on the far side of the moon in order to avoid local radio noise." Building an array on the moon is both financially and technically unfeasible at the moment. The current, more practical sites under consideration for LOFAR are in the southwestern United States, western Australia, and the Netherlands. Because of noise interference, the further away an extrasolar planet is from our solar system, the more difficult it will be to detect its radio emissions. "Even at the distance to the nearest star--Proxima Centauri, 1 parsec (3.258 light years) away--none of the planets in our own solar system would be detectable using the LOFAR array," notes Mutel. Hunting in the dark Despite the problems facing radio planet detection, it could offer some advantages over current, visual light techniques. The visual light techniques have never actually seen their quarry: at such great distances, weak planetary light is overwhelmed by the star's radiance. Planet hunters instead look for the subtle effects an orbiting planet exerts on its host star. Since more massive planets exert more detectable effects, all of the planets discovered so far are gas giants like Jupiter or Saturn. By searching for planetary radio emissions, however, Earth-sized planets possibly could be found. Provided that mass and magnetism are not related, the power of the radio emissions matters more than the mass of the planet. Another benefit of radio planet searches would be speed. Current detection techniques require astronomers to observe a star for more than one planetary orbit--that's why most of the extrasolar planets discovered to date are very close to their stars. For a planet orbiting from 1 AU, astronomers need at least two years of observations. Astronomers haven't been looking for extrasolar planets long enough to discover orbits further away than Jupiter's. With radio detection, however, planets far away from their stars would be more easily detected. Lazio says that a radio search could do a "quick look" sky survey, detecting planets in just a few hours or days. Besides just finding the extrasolar planets, radio emissions could tell us about a planet's magnetic field, the rotation rate, the spin axis, if there are any moons, and whether a planet is rocky or gaseous. Gallagher says extrasolar radio signals also would allow us to compare other solar systems with our own. Does solar wind from similar stars behave the same? Is there is a strong relationship between a planet's mass, age, and magnetic field properties? Such questions could start to be answered by comparing Aurora-related radio bursts. What's next? The project scientists currently are using the VLA to try to detect radio emissions from confirmed extrasolar planets. In the next 5 years, the scientists hope to use LOFAR to discover previously unknown planets. Once built, LOFAR will operate in the 10 to 250 MHz range. The radio telescope will do more than hunt for extrasolar planets. LOFAR will be able to study such things as the Earth's ionosphere, Coronal Mass Ejections of the Sun, and the most distant galaxies and quasars. Additional information on this article is available at http://www.astrobio.net/news/article263.html. _____________________________________________________________________ DIAMONDS REVEAL EARLY WATER WORLD OF EARTH By Robert Roy Britt From Space.com 5 September 2002 Thanks to some gracious access to diamonds by the prestigious mining company De Beers and other firms, geologists are cracking some of the precious stones apart, figuring out just how old they are and gaining clues to Earth's early development. The results support a theory that just more than 3.3 billion years ago Earth was mostly a water world with little of the land that would one day become continents. Steven Shirey and David James of the Carnegie Institution of Washington, along with a team of researchers, examined imperfect, cast-off gems donated by large diamond miners. Minerals trapped in the diamonds represent flaws that make the stones worth little or nothing as jewelry, but they can serve as geologic clocks, Shirey explained in a telephone interview with SPACE.com. Get the full story at http://www.space.com/scienceastronomy/planetearth/diamonds_020905.htm l. _____________________________________________________________________ MUDDY WATERS By Patrick L. Barry From NASA Science News 5 September 2002 Is it safe to swim in your local lake? Are the fish from that lake good to eat? NASA satellites will soon help find out. Dozens of shallow-draft bass fishing boats creep along the cypress- lined shore, each guided by a seasoned fisherman. It's the annual bass tournament everyone's been waiting for, yet the fish aren't biting. Tugging at the rim of his threadbare cotton fishing hat, one veteran angler eyes the clear blue sky above, the ripples on the lake surface, and the pattern of tree trunks and reeds along the water's edge. Sensing a clue, he toes the control of the trolling motor and glides slowly toward a shallow cove where a trophy-winning fish is certainly lurking--just out of view. Indeed, there's something there. But it's not a bass. Buried down in the sand and silt of the lake's bottom lies a rainbow of different noxious chemicals--relics of 100 years of industry in the region. The boat's trolling motors stir them up and so do wind- driven waves. The fisherman doesn't notice what's happening, but a satellite passing 400 km overhead does. It snaps a picture of the lake and beams the data to Earth, where scientists note areas of water that are less reflective than usual--a result of the stirred-up sediments. City officials and environmental regulators can't wait to see the data. They hope it will help answer some important questions: Are the lake's legendary bass fit for the dining room table? How much sediment is dumped into the lake by the adjoining river? Do pollutants buried in a patch of lakebed near an abandoned paper mill pose any threat to swimmers at a beach on the far side of the lake? And why is this year's tournament a bust? In real-life, they'll have to keep waiting. Satellite views of stirred-up murky water (scientists call it "resuspended sediments") aren't yet available to answer their questions. Currently, monitoring suspended sediments is done by hand, a challenge for bodies of water that cover hundreds or even thousands of acres. Scant data gathered at a few monitoring stations provide only a glimmer of what's going on. Around the country, there are dozens of reasons to monitor stirred-up sediments. Shellfish harvests in Northeastern bays, for example, are affected by sediment levels. So is the rich biodiversity of Atlantic, Pacific and Gulf coastal estuaries. Further inland, nutrients released by stirred-up sediments can nourish microscopic phytoplankton in freshwater lakes and trigger algal blooms that choke-off the lakes' plant and animal life. This need for wide-area monitoring is what has motivated scientists at NASA's Stennis Space Center in Mississippi to explore how satellites might help. And after 6 months studying Lake Pontchartrain, just north of New Orleans, Louisiana, they think they have a system that works. "We've talked to city planners, [environmental regulators, and other] decision makers--and they've said they would like this," says Richard Miller, chief scientist for NASA's Earth Science Applications Directorate and the manager of the project. Miller's team monitored Lake Pontchartrain using two instruments in space: NASA's SeaWiFS satellite and NOAA's Advanced Very High Resolution Radiometer (AVHRR). Both measure the reflectance of the water--an indicator of turbidity and stirring. A certain amount of stirring will occur just because of the action of wind-driven waves. This is called "natural resuspension." To account for it, Miller's group uses a computer model to calculate the expected amount of stirring based on wind speed, wind direction, and the depth and shape of the body of water. The computer runs its simulation and "spits out" a number the scientists call the "index of resuspension intensity." Plotted over the area of the body of water (in the form of false colors or contours) this number maps out the expected resuspension due to wind and waves. Pontchartrain, our index of resuspension intensity correlates really well with our satellite imagery," Miller says. Sometimes, though, they spot suspended particles in a place not predicted by the computer model. Such anomalies might be evidence of human activity-- such as fishing in shallow waters--or perhaps a movement of turbid water from another area, set in motion by a passing storm front. The results so far are "very encouraging," says Miller, but there's more to do. For example, each pixel in the images from these satellites represents one square kilometer on the ground, so the application of this remote sensing technology is currently limited to large bodies of water. The research team is now starting a new phase of field trials that incorporates a different satellite sensor that has better resolution. Called the MODerate-resolution Imaging Spectro-radiometer (MODIS), the pixels in images from this sensor are only 1/16th of a square kilometer on the ground. MODIS rides aboard two NASA satellites-- Terra and the recently launched Aqua--which together will provide two snapshots per day, one in the morning and one in the afternoon. The field trials have also expanded to a new site at Pamlico Sound in North Carolina. In collaboration with Reide Corbett of East Carolina University, this phase of the trials will focus on the effects of fishing trawls or bottom nets. Ultimately, the researchers want to construct a system for delivering an executive-summary version of the satellites' observations to the regulators and decision makers who need it. Miller says that his team's goal is to collaborate with decision makers in the region to design a system to suit their needs. He expects that the project could be producing these executive reports in six months' time. Putting this knowledge into the hands of decision makers will help keep our waterways clean, so that fishers in the future can safely make a meal of the day's catch, not just a trophy. Additional information on this article is available at http://science.nasa.gov/headlines/y2002/05sept_estuaries.htm?list6832 23. _____________________________________________________________________ RUNNEGAR TO LEAD NASA ASTROBIOLOGY INSTITUTE NASA/ARC release 02-100AR 6 September 2002 NASA today announced that it has selected Dr. Bruce Runnegar of the University of California, Los Angeles, as the next director of NASA's Astrobiology Institute (NAI). He succeeds Nobel Laureate Dr. Baruch S. Blumberg, who last year declared his intention to step down from the position. Runnegar currently is a professor in UCLA's Department of Earth and Space Sciences and the Institute of Geophysics and Planetary Physics (IGPP). For the past four years, he also has served as the Director of the IGPP's Center for Astrobiology, one of the 11 original lead teams of the Astrobiology Institute. Educated in Australia at the University of Queensland, Runnegar became a Fellow of the Australian Academy of Science in 1987. "Dr. Runnegar is an internationally recognized paleontologist and astrobiologist whose breadth of knowledge and excellence in research and teaching are respected throughout the scientific and academic communities," said Dr. Henry McDonald, Director of NASA Ames Research Center, in California's Silicon Valley. "We enthusiastically welcome him." "I am impressed as much with Dr. Runnegar's credentials and experience, as with his vision for the role the NASA Astrobiology Institute could play in meshing leading-edge research directions with NASA's unique exploration opportunities," said NASA Senior Scientist for Astrobiology, Dr. Michael Meyer. As director of the Institute, Runnegar will lead the consortium in its efforts to answer the three big questions central to astrobiology: How does life begin and evolve? Does life exist elsewhere? What is life's future on Earth and beyond? "The answers to these questions will not come quickly," said Runnegar. "That's why NASA needs to attract bright young people to the field of astrobiology." Part of his role, Runnegar said, will be to develop educational opportunities in parallel with new astrobiology science objectives. "Dr. Runnegar's appointment represents another major step in the evolution of the Astrobiology Institute and the work that it sponsors," said G. Scott Hubbard, NASA Ames Deputy Director for Research. "Runnegar's long-established leadership in the field will provide the NAI with continuing momentum and research growth." Established in July 1998, the NAI is a virtual organization composed of NASA field centers, universities and research organizations that collaborate to study the origin, evolution, distribution and future of life in the universe. The Institute brings together astronomers, biologists, chemists, geologists, paleontologists, physicists and planetary scientists. It comprises 15 lead teams selected from competitive, peer-reviewed proposals submitted in response to NASA Cooperative Agreement Notices or CANs. Leadership of the Institute, the Director's office and associated staff are located at NASA Ames. NAI's first director was G. Scott Hubbard, followed by Blumberg in 1999. "Good things come in threes," said NAI Deputy Director Dr. Rosalind Grymes. "In the next several months, the NAI will release its third call for collaborative research grants, hold its third general members' meeting and welcome its third director." Runnegar and his wife, Maria, a biochemist at the University of Southern California, have one daughter, who is a lawyer in Brisbane, Australia. He enjoys geological fieldwork, old furniture and botanical gardens. The NAI currently has 15 member institutions: Arizona State University, Tempe; University of Colorado, Boulder; University of Washington, Seattle; NASA Ames Research Center; Scripps Research Institute, La Jolla, Calif.; University of Rhode Island; Pennsylvania State University; Harvard University; University of California, Los Angeles; Michigan State University; Marine Biological Laboratory, Woods Hole, Mass.; Carnegie Institution of Washington; NASA Johnson Space Center, Houston; and two research teams located at the NASA Jet Propulsion Laboratory, Pasadena, CA. For additional information about the NASA Astrobiology Institute see http://nai.arc.nasa.gov. Contact: Kathleen Burton NASA Ames Research Center, Moffett Field, CA Phone: 650-604-1731 or 604-9000 E-mail: kburton@mail.arc.nasa.gov _____________________________________________________________________ HOUSTON, ARE WE THERE YET? By Trudy E. Bell From NASA Science News 9 September 2002 "Mom, are we there yet?" Every parent has heard that cry from the back seat of the car. It usually begins about 15 minutes after the start of any family trip. Good thing we rarely travel more than a few hundred or a few thousand miles from home. But what if you were traveling to, say, Mars? Even at its closest approach to Earth every couple years, the red planet is always at least 35 million miles away. Six months there and six months back-- at best. "Houston, are we there yet?" "Chemical rockets are just too slow," laments Les Johnson, manager for in-space transportation technologies at NASA's Marshall Space Flight Center. "They burn all their propellant at the beginning of a flight and then the spacecraft just coasts the rest of the way." Although spacecraft can be sped up by gravity assist--a celestial crack-the-whip around planets, such as the one around Saturn that flung Voyager 1 to the edge of the solar system--round-trip travel times between planets are still measured in years to decades. And a journey to the nearest star would take centuries if not millennia. Worse yet, chemical rockets are just too fuel-inefficient. Think of driving in a gas guzzler across a country with no gas stations. You'd have to carry boatloads of gas and not much else. In space missions, what you can carry on your trip that isn't fuel (or tanks for fuel) is called the payload mass--e.g., people, sensors, samplers, communications gear and food. Just as gas mileage is a useful figure of merit for the fuel efficiency of a car, the "payload mass fraction"--the ratio of a mission's payload mass to its total mass--is a useful figure of merit for the efficiency of propulsion systems. With today's chemical rockets, payload mass fraction is low. "Even using a minimum-energy trajectory to send a six-person crew from Earth to Mars, with chemical rockets alone the total launch mass would top 1,000 metric tons--of which some 90 percent would be fuel," said Bret G. Drake, manager for space launch analysis and integration at Johnson Space Center. The fuel alone would weigh twice as much as the completed International Space Station. A single Mars expedition with today's chemical propulsion technology would require dozens of launches--most of which most would simply be launching chemical fuel. It's as if your 1-ton compact car needed 9 tons of gasoline to drive from New York City to San Francisco because it averaged only a mile per gallon. In other words, low-performance propulsion is one major reason why humans have not yet set foot on Mars. More efficient propulsion systems increase the payload mass fraction by giving better "gas mileage" in space. Since you don't need as much propellant, you can carry more stuff, go in a smaller vehicle, and/or get there faster and cheaper. "The key message is: we need advanced propulsion technologies to enable a low-cost mission to Mars," Drake declared. Thus, NASA is now developing ion drives, solar sails, and other exotic propulsion technologies that for decades have whooshed humans to other planets and stars--but only in the pages of science fiction. From tortoise to hare What are the science-fact options? NASA is hard at work on two basic approaches. The first is to develop radically new rockets that have an order-of-magnitude better fuel economy than chemical propulsion. The second is to develop "propellant-free" systems that are powered by resources abundant in the vacuum of deep space. All these technologies share one key characteristic: they start slowly, like the proverbial tortoise, but over time turn into a hare that actually wins a race to Mars--or wherever. They rely on the fact that a small continuous acceleration over months can ultimately propel a spacecraft far faster than one enormous initial kick followed by a long period of coasting. Technically speaking, they're all systems with low thrust (meaning you would barely feel the oh-so-gentle acceleration, equivalent to that of the weight of a piece of paper lying on your palm) but long operating times. After months of continuing small acceleration, you'd be clipping along at many miles per second! In contrast, chemical propulsion systems are high thrust and short operating times. You're crushed back into the seat cushions while the engines are firing, but only briefly. After that the tank is empty. Fuel-efficient rockets "A rocket is anything that throws something overboard to propel itself forward," Johnson pointed out. (Don't believe that definition? Sit on a skateboard with a high-pressure hose pointed one way, and you will be propelled in the opposite way). Leading candidates for the advanced rocket are variants of ion engines. In current ion engines, the propellant is a colorless, tasteless, odorless inert gas, such as xenon. The gas fills a magnet-ringed chamber through which runs an electron beam. The electrons strike the gaseous atoms, knocking away an outer electron and turning neutral atoms into positively-charged ions. Electrified grids with many holes (15,000 in today's versions) focus the ions toward the spaceship's exhaust. The ions shoot past the grids at speeds of up to more than 100,000 miles per hour (compare that to an Indianapolis 500 racecar at 225 mph)--accelerating out the engine into space, so producing thrust. Where does the electricity come from to ionize the gas and charge the engine? Either from solar panels (so-called solar electric propulsion) or from fission or fusion (so-called nuclear electric propulsion) [would supply the energy]. Solar electric propulsion engines would be most effective for robotic missions between the sun and Mars, and nuclear electric propulsion for robotic missions beyond Mars where sunlight is weak or for human missions where speed is of the essence. Ion drives work. They've proven their mettle not only in tests on Earth, but in working spacecraft--the best-known being Deep Space 1, a small technology-testing mission powered by solar electric propulsion that flew by and took pictures of Comet Borrelly in September, 2001. Ion drives like the one that propelled Deep Space 1 are about 10 times as efficient as chemical rockets. The lowest-mass propulsion systems, however, may be those that carry no on-board propellant at all. In fact, they're not even rockets. Instead, in true pioneer style, they "live off the land"--relying for energy on natural resources abundant in space, much as pioneers of yore relied for food on trapping animals and finding roots and berries on the frontier. The two leading candidates are solar sails and plasma sails. Although the effect is similar, the operating mechanisms are very different. A solar sail consists of an enormous area of gossamer, highly reflective material that is unfurled in deep space to capture light from the sun (or from a microwave or laser beam from Earth). For very ambitious missions, sails could range up to many square kilometers in area. Solar sails take advantage of the fact that solar photons, although having no mass, do have momentum--several micronewtons (about the weight of a coin) per square meter at the distance of Earth. This gentle radiation pressure will slowly but surely accelerate the sail and its payload away from the sun, reaching speeds of up to 150,000 miles per hour, or more than 40 miles per second. A common misconception is that solar sails catch the solar wind, a stream of energetic electrons and protons that boil away from the Sun's outer atmosphere. Not so. Solar sails get their momentum from sunlight itself. It is possible, however, to tap the momentum of the solar wind using so-called "plasma sails." Plasma sails are modeled on Earth's own magnetic field. Powerful on- board electromagnets would surround a spacecraft with a magnetic bubble 15 or 20 kilometers across. High-speed charged particles in the solar wind would push the magnetic bubble, just as they do Earth's magnetic field. Earth doesn't move when it's pushed in this way--our planet is too massive. But a spacecraft would be gradually shoved away from the Sun. (An added bonus: just as Earth's magnetic field shields our planet from solar explosions and radiation storms, so would a magnetic plasma sail protect the occupants of a spacecraft.) Of course, the original, tried-and-true propellant-free technology is gravity assist. When a spacecraft swings by a planet, it can steal some of the planet's orbital momentum. This hardly makes a difference to a massive planet, but it can impressively boost the velocity of a spacecraft. For example, when Galileo swung by Earth in 1990, the speed of the spacecraft increased by 11,620 mph; meanwhile Earth slowed down in its orbit by an amount less than 5 billionths of an inch per year. Such gravity assists are valuable in supplementing any form of propulsion system. Okay, now that you've zipping through interplanetary space, how do you slow down at your destination enough to go into a parking orbit and prepare for landing? With chemical propulsion, the usual technique is to fire retrorockets--once again, requiring large masses of onboard fuel. A far more economical option is promised by aerocapture--braking the spacecraft by friction with the destination planet's own atmosphere. The trick, of course, is not to let a high-speed interplanetary spacecraft burn up. But NASA scientists feel that, with an appropriately designed heat shield, it would be possible for many missions to be captured into orbit around a destination planet with just one pass through its upper atmosphere. Onward! "No single propulsion technology will do everything for everybody," Johnson cautioned. Indeed, solar sails and plasma sails would likely be useful primarily for propelling cargo rather than humans from Earth to Mars, because "it takes too long for those technologies to get up to escape velocity," Drake added. Nonetheless, a hybrid of several technologies could prove to be very economical indeed in getting a manned mission to Mars. In fact, a combination of chemical propulsion, ion propulsion, and aerocapture could reduce the launch mass of a 6-person Mars mission to below 450 metric tons (requiring only six launches)--less than half that attainable with chemical propulsion alone. Such a hybrid mission might go like this. Chemical rockets, as usual, would get the spacecraft off the ground. Once in low-Earth orbit, ion drive modules would ignite, or ground controllers might deploy a solar or plasma sail. For 6 to 12 months, the spaceship-- temporarily unmanned to avoid exposing the crew to large doses of radiation in Earth's Van Allen radiation belts--would spiral away, gradually accelerating up to a final high Earth-departure orbit. The crew would then be ferried out to the Mars vehicle in a high-speed taxi; a small chemical stage would then kick the vehicle up to escape velocity, and it would head onward to Mars. As Earth and Mars revolve in their respective orbits, the relative geometry between the two planets is constantly changing. Although launch opportunities to Mars occur every 26 months, the optimal alignments for the cheapest, fastest possible trips happen every 15 years--the next one coming in 2018. Perhaps by then we'll have a different answer to the question, "Houston, are we there yet?" Additional information on this article is available at http://science.nasa.gov/headlines/y2002/09sept_spacepropulsion.htm?li st52260. _____________________________________________________________________ MARS EXPLORER ROVER 2003 LANDING SITES From Astrobiology Magazine 9 September 2002 From the start, the Mars research community had to survey in detail more than 150 landing sites to touch down their 2003 Mars Explorer Rover (MER). Scheduled for launch in mid-2003 (May and June), the MER project's twin landers and rovers will follow a similarly thrilling descent as the 1997 Mars Pathfinder. Parachutes and a rocket-braking, followed by airbag bounces, will determine the spacecraft's final resting location. In preparation, the delicate balance must be struck between science and safety as the team narrows the choices for final explorer sites. Using high-resolution orbital imagery from the Mars Orbital Camera (or MOC), the 150 sites were initially graded for safety and scientific wealth. The MOC takes images of the surface with a resolution as much as 50 times greater (as fine as meters per pixel) than the previously available pictures taken by the Viking spacecraft more than two decades ago. The many factors that influenced their decision-making included high winds, day-to-night temperature extremes, slopes, rockiness, and the hopes of finding ancient evidence of a fascinating geological and potentially water-filled past. Let's rock As scientists get more detailed views of the surface, Mars topology is increasingly viewed as a very active landscape--shaped by tornadoes, dust devils, regional and even global dust storms. Particularly bad during the summer and spring, dust can envelop the entire planet on a seasonal cycle of surface and atmospheric heating. As expected from such sweeping winds, fields of dunes and sandstorms have been observed as part of the contouring forces that fill in behind meteor impacts, cratering, and the Red Planet's volcanic history. Weather on Mars High winds pose a dual challenge to mission planners. Because the crafts are scheduled to descend during the martian afternoon (to maintain clearer Earth-communications), martian winds can whip and rock the landers just when solar-heating and thus gusts reach their maximum. Like any landing airplane, the winds make true height detection a difficult task. But any side-to-side swings also pose an additional risk, since the rocket-braking can potentially add rather than subtract from the descent-speed if the landers pitch or even invert momentarily. Once safely grounded, weather prediction takes on much importance for mission planners. If an unexpected storm visited the landing site, many of which can last 90 days regionally without pause, then the mission has to negotiate power, communications and general hardware safety over the length of its expected 90 day life. Interestingly, a 2001 global dust storm on Mars is often compared to the effects of the 1991 Mt. Pinatubo eruption on Earth, because of changes in atmospheric aerosols, temperature changes and planet-wide effects from a single event. Frigid electronics Mars undergoes not only an extreme seasonal range of winds and temperatures, but also a rapid heating and cooling cycle during a single day. It is not uncommon to find a 100 degree F (60 C) high and low on the same martian day (or sol). Away from the equator, maximum daytime temperatures reach only -22°F (-30°C), while, on the equator, this can rise to over 72°F (22°C). But daytime is nothing compared to the frigid nights on Mars. Because the thin atmosphere is a poor heat retainer, in even the warmest of places night-time temperatures fall to around -148°F (-100°C). State-of-the-art insulation is needed to keep the sensitive electronics warm while still not bulking up the mass or hindering the mobility of the rover and lander twins. The mission planning for a Mars lander has to guess at local conditions years in advance, and compensate for swings that might daunt even the most intrepid Earth-bound weather station. The envelope please From consideration of the 150 candidate sites, the MER teams appear to have narrowed their choices to two. Both are equatorial sites, avoiding the thermal stresses of the polar regions. Their science targets highlight the possibilities to explore some of the newly- found sediments and ancient water-eroded areas. Terra Meridiani: testing the wet hypothesis The first site is called Terra Meridiani (located 3°S to 0°N latitude, 352°E to 1°E longitude). Extending for hundreds of miles in extent, Terra Meridiani has rocky outcrops that might roughly be compared to the terrain of parts of Utah or northern Arizona. The patchwork of bright and dark regions seems to be scarred by all the potentially interesting epochs on Mars as layered views into its past: volcanism, sedimentation, wind erosion, and early crustal history. But remarkably free from cratering, many Mars scientists have wondered what forces might have shaped the unique orbital views of this equatorial region. The relative absence of fresh impact craters points to a geologically young area. So un-Mars-like is the selected area that those MOC scientists who have seen Mars daily at the scale of a small school bus have remarked: "If I'd seen this landscape used in a movie about Mars five years ago, I'd have said the director had no clue what Mars is supposed to look like." But foremost, it is Terra Meridiani's rich source of a particular grey crystalline mineral called hematite that caught the attention of scientists. Considered one of the key discoveries of the Mars Global Surveyor mission, magnetite detection has revealed the gray crystals mainly concentrated around Terra Meridiani. On Earth, hematite is almost always formed in ways that require aqueous fluids and groundwater leaching to give it the unique crystalline qualities. But in some terrestrial examples (as unearthed in Chile and Mexico), iron-rich fluids can also give the same layered effects as seen on Mars, even without water. Indeed the May 2002 publication by Brian Hynek, et al. (Washington University, St. Louis) in the Journal of Geophysical Research concluded that the mineral may have originated from oxidation (or rusting) of lava outflows, followed by precipitation and deposit from fluid flow much later. So unraveling the climate history of Mars will depend on understanding the complex interplay between its ancient volcanism and water balance--a "wet" hypothesis to be tested actively at Terra Meridiani because of its rich hematite deposits. Gusev Crater: ancient lakebed? The second site, called Gusev Crater (located at 14.6°S, 184.6°W), appears to be the site of an ancient lakebed. In Greek, Gusev refers to "cup". Since the early Mariner and Viking images, the crater and adjoining valley first revealed a site rich to explore further in search of sedimentary deposits. The crater stretches approximately 150 kilometers (93 miles) across. Ma'adim Vallis, in the martian southern cratered uplands, is one of the largest valley networks on the planet, and first became classified as a runoff channel in 1975 (Sharp, R. P., and M. C. Malin, 1975, Channels on Mars. Geological Society of America Bulletin, v. 86, p. 593-609). Ma'adim Valley, is over 900 km long and named after the Arabic name for the Red Planet. One of the first things noticed about the crater was its marked asymmetry--perhaps a legacy of a half-filled shoreline or pond concentrated on a tilt. Nathalie Cabrol and colleagues at NASA Ames Research Center, the Vernadksy Institute in Moscow, and Arizona State University published in 1998 (Icarus) their study of the valley and impact crater on Mars which together point to a prolonged history of water-related activity. The researchers established a sequence of events for the Ma'adim Vallis/Gusev crater area that included flowing water, ponding, and sedimentation over a period of a couple of billion years. Because of the sheer variety of smooth terraces and layering, water in Gusev Crater might have ponded around 1.8 billion years ago--following a huge impact that formed the crater and rim (about 3.5 billion years ago). This natural collector basin supported the Ma'adim Vallis sediment, which could be hundreds of meters thick. Such a varied history makes Gusev crater a prominent depositional site and, a key location for future astrobiological explorations on Mars. In 1995, Gusev crater was included in NASA's report, "An Exobiological Strategy for Mars Exploration" (NASA Publication SP- 530) as a priority site for future biological exploration. What's next One enhanced feature of the MER mission plan is more mobility for the rovers. These bigger Mars Exploration Rovers (MER) can trek up to a football field--330 feet (100 meters)--per martian day. Making remote maneuvers over those distances means getting very good topological maps, while knowing where every interesting rock or hazard might tip and block the rovers' paths. Seen globally, the darker areas on Mars are generally rockier while the bright areas are dusty, but a much enhanced topography goes into site selection beforehand, and then much later after landing to roam the surface. Potentially hundreds or thousands of pebbles and boulders can pock mark a landing site on the scale of a 100 yards per day. In total, the football field milestone is almost as far in one martian day as the 1997 Sojourner rover did over its entire, many-month-long lifetime. Starting in January 2004, MER surface operations will last for at least 90 martian days, or longer if hardware health is maintainable. Once an interesting target is identified on the ground, the Mars Rovers' will employ what is their primary science payload, a collection of 5 instruments called the Athena package. Mission planners look forward to even more close-up views of the two primary sites slated for the early 2004 rendezvous. Reference: Cabrol, N. A., E. A. Grin, R. Landheim, R. O. Kuzmin, R. Greeley, 1998, Duration of the Ma'adim Vallis/Gusev Crater Hydrogeologic System, Mars. Icarus, v. 133, p. 98-108. Additional information on this article is available at http://www.astrobio.net/news/article265.html. _____________________________________________________________________ NEW ADDITIONS TO THE ASTROBIOLOGY INDEX By David J. Thomas http://www.lyon.edu/webdata/users/dthomas/astrobiology/astrobiology.h tml 9 September 2002 Astrobiology, exobiology and terraformation articles http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s1.html ESA, 2002. No place to hide from Mars Express. Spaceflight Now. Terrestrial extreme environments articles http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s2.html L. Mullen, 2002. Extreme animals. Astrobiology Magazine. Evolutionary biology and chemistry articles http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s5.html R. R. Britt, 2002. Diamonds reveal early water world of Earth. Space.com. _____________________________________________________________________ CASSINI SIGNIFICANT EVENTS NASA/JPL release 29 August - 6 September 2002 The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, September 4. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at http://saturn.jpl.nasa.gov/cassini/english/where/. On-board activities this week included Radio and Plasma Wave Science High Frequency Receiver calibrations, an autonomous Solid State Recorder Memory Load Partition repair activity, and clearing of the ACS high water marks. To support critical Integrated Test Laboratory (ITL) activities, building 230 generators were left running over the weekend. On Tuesday, power was switched back to Edison through the Uninterrupted Power Supply (UPS). The system had been checked out over the past weeks with no problems observed. The switch-over went smoothly. The UPS batteries supply short-term power and allow time to switch to the generators if there is a problem with Edison power. It was reported at the weekly Multi-mission Activities Planning Teleconference that having the building 230 UPS system in operation the past few days prevented a few dips in Edison power from causing problems. Edison has been working to prevent problems due to the fires in the area. Visual and Infrared Mapping Spectrometer (VIMS) flight software version 5.1 was approved at a Software Requirements Certification Review meeting for uplink to the spacecraft in October. The VIMS instrument team released a draft evaluation of the Science Opportunity Analyzer tool. The team found it a very capable tool and responded that with a few refinements and bug fixes, and a near term official Cassini release, the team would be able to make very good use of the product. Phase one of a Workforce Analysis Study was presented at this week's Cassini Design Team meeting. Three tour process were included, the Science Operations Plan Update Process, Science and Sequence Update Process, and the Maneuver Process. The period time selected for the study included part of tour sequences S12 through S18, and 18 separate maneuvers. Future updates will include sequence adaptability, and real time commanding processes. Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, CA, manages the Cassini mission for NASA's Office of Space Science, Washington, DC. _____________________________________________________________________ INTERNATIONAL SPACE STATION SCIENCE OPERATIONS STATUS REPORT NASA/MSFC release 02-216 4 September 2002 Research that could lead to electronic materials with improved opto- electronic properties was set to resume today aboard the International Space Station. Flight Engineer Peggy Whitson was scheduled to install a sample and initiate the sixth test of the Solidification Using a Baffle in Sealed Ampoules (SUBSA) experiment. SUBSA is investigating semiconductor manufacturing processes. Materials scientists want to make better semiconductor crystals to be able to further reduce the size of high-tech devices. Semiconductor crystals are found in computer chips, sensors for medical imaging equipment and detectors of nuclear radiation. Impurities, or dopants, in semiconductors are used to control their properties. Uniform distribution of the dopant is essential to achieve the desired properties. The goal of SUBSA is to identify what causes the motion in melted materials processed in space and to reduce the magnitude of the motion so that it does not interfere with semiconductor production. SUBSA research was suspended last month after a quartz sample tube cracked during heating. Operations resumed following a safety review by the science team on the ground and cleanup work by Whitson inside the Microgravity Science Glovebox, where the SUBSA experiment is located. Additional SUBSA experiments are tentatively planned for September 10, 11 and 15. On Friday and Saturday, August 30-31, Whitson replaced the smoke detector in EXPRESS Rack 2. The rack remained powered off this week due to an electrical grounding strap broken during the changeout. There are no active payloads in the rack currently. The payload operations team is looking at replacing the strap. A plan is in place to make a strap onboard out of two system rack straps that could be used until a new strap is launched on a future Shuttle mission. Also today, selected crewmembers were scheduled to participate in the Crew Interactions experiment, which examines interpersonal factors that can affect the performance of the crew and ground support personnel during long missions. Participating crew fill out the questionnaire on the Human Research Facility laptop computer. Photography subjects for the Crew Earth Observations project this week included: lakes recently built on the Euphrates River in southwestern Turkey, air quality in the Western Mediterranean, Seattle and Dallas in the United States, Lake Eyre in Australia, the Toshka Lakes of Egypt, fires burning in Angola, air quality in Southeast Africa and the lower Amazon River Basin. Automated experiments involving biological materials, space construction materials, the station's vibration environment, and plant growth continued to function well aboard the Station, while liver cell, petroleum processing and drug delivery experiments have been completed and are stored for return to scientists on Earth. The crew continued its daily payload status checks to make sure that all experiments and payload facilities continue to operate properly. The Payload Operations Center at NASA's Marshall Space Flight Center in Huntsville, AL, manages all science research experiment operations aboard the International Space Station. The center is also home for coordination of the mission-planning work of a variety of international sources, all science payload deliveries and retrieval, and payload training and payload safety programs for the Station crew and all ground personnel. Contact: Steve Roy Media Relations Department Phone: 256-544-0034 E-mail: Steve.Roy@msfc.nasa.gov _____________________________________________________________________ MARS ODYSSEY THEMIS IMAGES NASA/JPL/ASU release 3-6 September 2002 Viking Lander 2 Anniversary (Released 3 September 2002) http://themis.la.asu.edu/zoom-20020903A.html Terby Crater (Released 4 September 2002 http://themis.la.asu.edu/zoom-20020904a.html Fluidized crater ejecta (Released 5 September 2002) http://themis.la.asu.edu/zoom-20020905a.html Ares Valles (Released 6 September 2002) http://themis.la.asu.edu/zoom-20020906a.html All of the THEMIS images are archived at http://themis.la.asu.edu/latest.html. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, DC. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena. _____________________________________________________________________ STARDUST STATUS REPORT NASA/JPL release 6 September 2002 All subsystems were performing normally during the spacecraft's one scheduled period of contact through the Deep Space Network in the past week. Mirror alignment for the Navigation Camera was calibrated, using new software for pattern-matching and selecting small windows of interest within larger fields of view. A total of 23 images were taken for the calibration. Five are full-frame images and 18 are pattern-matched and windowed images. Playback will be completed next week. The windowed images were taken at 10-degree steps of mirror pointing, up to 180 degrees. Indications are that the full-frame images were successful. Some of the windowed images may not have included enough stars for the pattern-matching to work. Star images may have been too dim or too smeared to be detected at the brightness threshold set by the software. Enough of the windowed images will be successful to help engineers understand the camera performance and assess what detection threshold level to set in the future. Representatives of the Genesis Project and of the Utah Test and Training Range met for an annual planning update. This military range is where Genesis will return its collected sample material to Earth in September 2004. The meeting's participants discussed operations prior to and during Earth entry, tracking during Earth entry and landing, handling of the return capsule at the recovery site and preparation of the capsule at a hanger for aircraft delivery to the Johnson Space Center Curatorial Facility in Texas. The collected particles will be analyzed and curated at the Johnson facility. The Utah Test and Training Range is under high security, and maintaining the integrity of the sample-return capsule is an absolute necessity, so accommodating anyone other than key personnel near the capsule will be difficult. For more information on the Stardust mission--the first ever comet sample return mission--please visit the Stardust home page at http://stardust.jpl.nasa.gov. _____________________________________________________________________ End Marsbugs, Volume 9, Number 33.