MARSBUGS: The Electronic Astrobiology Newsletter Volume 7, Number 46, 4 December 2000. Editors: Dr. David J. Thomas, Math and Science Division, Lyon College, Batesville, AR 72503-2317, USA. dthomas@lyon.edu Dr. Julian A. Hiscox, 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 quarterly 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 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. Article contributions are welcome, and should be submitted to either of the two editors. Contributions should include a short biographical statement about the author(s) along with the author(s)' correspondence address. Subscribers are advised to make appropriate inquiries before joining societies, ordering goods etc. Back issues and Adobe Acrobat PDF files suitable for printing may be obtained from the official Marsbugs web page at http://welcome.to/marsbugs. The purpose of this newsletter is to provide a channel of information for scientists, educators and other persons interested in exobiology and related fields. This newsletter is not intended to replace peer- reviewed journals, but to supplement them. We, the editors, envision Marsbugs as a medium in which people can informally present ideas for investigation, questions about exobiology, and announcements of upcoming events. Astrobiology is still a relatively young field, and new ideas may come from the most unexpected places. Subjects may include, but are not limited to: exobiology and astrobiology (life on other planets), the search for extraterrestrial intelligence (SETI), ecopoeisis and terraformation, Earth from space, planetary biology, primordial evolution, space physiology, biological life support systems, and human habitation of space and other planets. --------------------------------------------------------------------- CONTENTS 1) LIFE UNDER BOMBARDMENT From the NASA Astrobiology Institute 2) VOLUNTEERS NEEDED FOR FLASHLINE CREW: HARD WORK, NO PAY, ETERNAL GLORY From The Mars Society 3) 4TH INTERNATIONAL MARS SOCIETY CONVENTION SLATED FOR STANFORD UNIVERSITY From The Mars Society 4) THREE TEAMS SELECTED FOR ROVER PROJECT From The Mars Society 5) ANCIENT SOUTH AFRICAN SOILS POINT TO EARLY TERRESTRIAL LIFE Pennsylvania State University release 6) ASTROBIOLOGISTS FIND EVIDENCE OF EARLY LIFE ON LAND NASA Ames release 00-79AR 7) LUNAR METEORITE AGES STRONGLY SUPPORT 'LUNAR CATACLYSM' By Lori Stiles 8) DRIED-UP SEA BEDS FOUND ON MARS By Jonathan Leake 9) NEW ADDITIONS TO THE ASTROBIOLOGY, EXTREME ENVIRONMENTS AND TERRAFORMATION INDEX By David J. Thomas 10) CASSINI WEEKLY SIGNIFICANT EVENTS JPL release 11) NASA'S MARS GLOBAL SURVEYOR SPIES FROSTY CRATERS JPL image advisory 12) STARDUST STATUS REPORT JPL release --------------------------------------------------------------------- LIFE UNDER BOMBARDMENT From the NASA Astrobiology Institute 28 November 2000 No one knows when life first established a firm foothold on Earth. Ask around in the scientific community, though, and you'll probably hear that the surface of early Earth, before about 3.8 billion years ago, was too hostile an environment for even a lowly microbe to set up shop. The main problem, as the conventional argument goes, was that between around 4.1 and 3.8 billion years ago, comets and asteroids were constantly bombarding Earth. The disastrous effects of these impacts would have rendered the Earth's surface uninhabitable. Not necessarily so, say a team of astrobiologists who are studying the oldest known sedimentary rocks on Earth. They have come to the conclusion that conventional wisdom on the subject may need some revision. Their conclusions will be published in a forthcoming issue of the Journal of Geophysical Research. The rocks in question appear to be a banded iron formation, or BIF, from Akilia Island in West Greenland. BIFs were deposited on Earth's ocean floors during the first 2 billion years of the planet's history. Iron and oxygen present in the oceans combined to form rust, which settled to the sea floor in layered sediments. Movements of the Earth's crust later pushed some of these sediments to the surface, where they can now be studied. It's not possible to date the Akilia BIF sediments directly because they have undergone metamorphism-pressure cooking-so that traditional radioactive dating techniques cannot be used to determine their age. But jutting into these sediments are younger igneous rocks that can be accurately dated with these techniques. An earlier analysis of this igneous rock, performed by a group headed by Dr. Allen Nutman of the Australian National University, put its age at 3.85 billion years. And because the igneous rock intrudes into the banded iron formation, it must have formed later than the sediments did. So the Akilia sediments must have been formed at least 3.85 billion years ago. Exactly how old they are, there is no way to know. But they are more ancient than any other sedimentary rocks found so far on Earth. Rocks this old are rare on Earth because tectonic recycling action has crushed, buried and melted all of the material that formed the Earth's crust during its first half-billion years of existence. Finding sedimentary rocks this old is important to geologists because they provide invaluable clues about what Earth was like in its early years. Few people dispute the notion that between 4.1 and 3.8 billion years ago, our planet was heavily bombarded by debris from space, a period known as the Late Heavy Bombardment. If you look up at a full moon on a clear night, you see that its surface is riddled with impact craters. Scientists who study the size and distribution of those craters see clear evidence that the Moon underwent an intense period of impacts between 4.1 and 3.8 billion years ago. Although no craters from this time remain on Earth, because the Earth and Moon are so near each other, the assumption is that Earth suffered a similar fate. Ariel D. Anbar, an Assistant Professor in the Department of Earth and Environmental Sciences at the University of Rochester, working with Gail L. Arnold, a graduate student, decided to look for traces of this bombardment in the Akilia sediments. Comets and asteroids contain greater quantities of the chemical element iridium than does the Earth's crust. So Anbar and Arnold, members of the NASA Astrobiology Institute (NAI), probed the Akilia sediments for abnormally high traces of iridium. They didn't find them. "Our naive expectation going in," explained Anbar, was that "these sediments date from this bombardment period, so we should see evidence of the bombardment in them, right? So we looked for iridium in these rocks and didn't find any. They were clean as a whistle." But earlier study of the Akilia sediments by one of Anbar's collaborators, Steve Mojzsis, had turned up a very different type of signature in the Akilia formation-a signature of biological activity. Mojzsis, also a member of the NAI, performed his analysis of the Akilia sediments while at the University of California San Diego. Carbon atoms come in two distinct forms, or isotopes. Carbon-12 atoms, the lighter of the two, contain 6 neutrons; carbon-13 atoms contain 7 neutrons. Microorganisms that take in carbon dioxide prefer to use the lighter carbon-12 atoms to construct the organic building blocks of which they are made. When ancient ocean-dwelling organisms died, the carbon that was formerly part of their living tissue settled to the ocean floor, becoming part of the sedimentary material deposited there. When Mojzsis found that the Akilia sedimentary rock samples contained higher-than-normal quantities of carbon-12, he concluded that biological activity must have been taking place at the time the sediments were formed-at least 3.85 billion years ago. So Anbar, Arnold and Mojzsis were faced with seemingly contradictory evidence. Life appeared to have been flourishing during the period of the Late Heavy Bombardment, at a time when Earth's surface was thought to be uninhabitable. And traces of the bombardment were nowhere to be found in the Akilia rocks. The solution lay in quantifying more carefully the effects of bombardment, using models developed by NAI member Kevin Zahnle at the NASA Ames Research Center. The essence of these models is that they treat the bombardment as a series of impact episodes, rather than assuming continuous pummeling of the Earth. They also take into account that smaller impact events are far more common than larger ones. The Akilia sediments would not be expected to contain telltale traces of extraterrestrial iridium unless a massive asteroid had slammed into the Earth, spewing iridium into the global environment, precisely during the period when the Akilia formation was being deposited. Zahnle's models indicate, however, that even during the Late Heavy Bombardment, such massive impacts were rare-too rare for there to be much chance of seeing their signs in sediments like those found on Akilia Island. So it made perfect sense that the sediments didn't contain elevated levels of iridium. Anbar and his colleagues reason that if the bombardment had a smaller-than-expected effect on the composition of sediments, it may also have had a smaller-than-expected effect on early life. Although small impacts were more common during the Late Heavy Bombardment than at any time since then, each such impact would destroy life at the surface only in one small area, not globally. Only the rarest, most massive impacts had the potential to wipe out all life on the planet's surface. Zahnle's models indicate such impacts occurred only once every ten to one hundred million years. Moreover, the worst of their effects lasted for only about ten thousand years, after which time conditions on the Earth's surface returned to normal. "So during most of this violent period of Earth's history," says Anbar, "the Earth's surface- if you're a microbe, anyway-was a perfectly balmy place to be. Which runs contrary to this picture that is out there that this was a very inhospitable period of time for life." What next? Getting above the surface That still leaves open one important question: Where could life hang out in safety during those rare, massive impact events that caused the surface literally to boil away? One suggestion is that hydrothermal vents might have filled that role. If life migrated down to these vents-or perhaps even began there-it could have continued on during major impact events, oblivious to what was going on the surface. And when the environment topside returned to habitability, life could have moved back up and recolonized the surface. "So as long as microorganisms had places on the Earth where they'd be sheltered from really massive impact events," concluded Anbar, "there's no reason that they couldn't have repopulated the surface multiple times. And therefore there's no reason not to expect to find evidence of life if you find sediments from the earth's surface during the period of heavy bombardment." For more information on this article, see http://nai.arc.nasa.gov/index.cfm?page=lifebombard. --------------------------------------------------------------------- VOLUNTEERS NEEDED FOR FLASHLINE CREW: HARD WORK, NO PAY, ETERNAL GLORY From The Mars Society 28 November 2000 The Mars Society is requesting volunteers to participate as members of the crew of the Flashline Mars Arctic Research Station during an extended simulation of human Mars exploration operations on Devon Island during the summer of 2001. It is anticipated that the field season will run from late June through late August; volunteers should state during what segments of this span they are available. Both volunteer investigators who bring a new proposed program of research compatible with the objectives of Flashline Station, and volunteers simply wishing to participate as crewmembers supporting ongoing investigations will be considered. Applications will be considered from anyone in good physical condition above 18 years of age without regard to race, creed, color, gender, or nation. Scientific, engineering, practical mechanical, first aid, wilderness, and literary skills are all considered a plus. Dedication to the cause of human Mars exploration is an absolute must, as conditions are likely to be tough and the job will be very trying. Team spirit is essential. Those selected will be required to participate in short (a few days) crew training exercises to take place in the western United States during the spring of 2001, and to act under crew discipline and strict mission protocols during the field season on Devon Island. The Mars Society will pay travel and related expenses during training and field deployment, but aside from potential student stipends, there will be no salary. Applications including resume, character references, a brief letter explaining why you wish to participate, and a summary of any proposed research should be sent to Mars Society, PO Box 273, Indian Hills, CO 80454 no later than January 31, 2001. Total length of applications should not exceed three pages. Please include seven copies of the entire application in addition to the original. Members of the Flashline Management Committee will review submitted applications. Applications will not be accepted by email. If you have specific questions regarding this announcement please direct them to the appropriate email address. General inquiries: volunteers@marssociety.org Media inquiries: rzubrin@marssociety.org --------------------------------------------------------------------- 4TH INTERNATIONAL MARS SOCIETY CONVENTION SLATED FOR STANFORD UNIVERSITY From The Mars Society 28 November 2000 The Mars Society will hold the fourth annual convention at Stanford University, in Stanford, California, August 23 - 26, 2001. Dr. Bruce Lusignan, Mars Society steering committee member and Stanford professor, will act as our sponsor on campus. Sam Burbank and the Northern California chapter of the Mars Society have volunteered to help coordinate the event. As at Ryerson last year, we will be offering dormitory rooms at Stanford this summer. There are limited hotel accommodations in the area with relatively high prices, so we expect the dorm rooms to be quite popular. Information on conference and dorm registration will be posted on the web site around the first of the year. We are very excited about the Stanford venue and expect to attract many interesting guests and speakers. In 2001 we will be continuing the tradition of the Hakluyt contest. This contest provides a trip to the conference for the winner and wonderful Bushnell telescopes to finalists. Winners are chosen based on the best letter sent to public figures advocating the exploration of Mars. All entries should be sent to The Mars Society, P.O. Box 273, Indian Hills, CO 80454 or emailed to mzubrin@aol.com. In addition, we will again be sponsoring a contest for a poster for the convention. Over the last three years, it has been our pleasure to recognize outstanding volunteers at the annual banquet. This year, we are opening up the recognition process to a nominating procedure. Nominations will be accepted from chapters or from individuals. Nominations should include specifics about the outstanding efforts of the member. Please email your nominations to mzubrin@aol.com. --------------------------------------------------------------------- THREE TEAMS SELECTED FOR ROVER PROJECT From The Mars Society 28 November 2000 The Mars Society has selected three teams to develop analog Mars pressurized rovers to be used as part of our program of global Mars analog operations research in polar and desert environments. The three teams selected, out of an initial pool of 22 competitors, were the Australian "Team Marsupial," based out of the University of Queensland, Brisbane; the Michigan Mars Rover Design Project, based out of the University of Michigan, Ann Arbor; and the ARES team supported by allied groups at the University of Toronto and MIT. Each of the teams selected included over fifty participants, with the large majority consisting of undergraduate engineering students. The MIT/Toronto team is led by Vesna Nikolic (vesna@pdwe.com), the Australian team by Ben Cairns (einre@uq.net.au), and the Michigan team by Patrick Hunt (rover @umich.edu). Those wishing to volunteer their services in support of one of these projects should contact the team leaders. The three teams took three different, but equally valid approaches to developing an analog rover at low cost. Initial versions of the rovers will be complete and ready for preliminary field testing in either the American or Australian deserts as early as the fall of 2001. Tom Hill (hillkid@earthlink.net) is managing the overall rover project for the Mars Society. Information on the designs as they develop will be posted at the Mars Society web site at http://www.marssociety.org/projects/rover/. --------------------------------------------------------------------- ANCIENT SOUTH AFRICAN SOILS POINT TO EARLY TERRESTRIAL LIFE Pennsylvania State University release 29 November 2000 Remnants of organic matter in ancient soil more than 2.6 billion years old may be the earliest known evidence for terrestrial life, according to a team of Penn State astrobiologists. "Our work shows that the organic matter in this soil very probably represents remnants of microbial mats that developed on the soil surface between 2.6 and 2.7 billion years ago," says Dr. Hiroshi Ohmoto, professor of geochemistry and director of The Penn State Astrobiology Center. "This places the development of terrestrial biomass more than 1.4 billion years earlier than previously reported." Evidence that microorganisms flourished in the oceans since at least 3.8 billion years ago exists, but when these microorganisms colonized on land is not clear. The oldest undisputed remnants of terrestrial biomass have been 1.2 billion-year-old microfossils found in Arizona. Examining samples taken from Mpumalanga Province, South Africa, using a variety of geochemical methods, the researchers report in this week's issue of Nature, that a paleosol dating to between 2.6 and 2.7 billion years ago contains organic carbon that was neither created by high temperature fluids nor is the remnant of later petroleum migration, but is in situ biological in origin. A paleosol is a layer of ancient soil, in this case buried and preserved where it formed. Because the 55-foot thick layer of soil found at Schagen is located between a layer of 2.7 billion-year-old serpentine and a 2.6 billion-year-old quartzite bed, the researchers can date the soil to between 2.6 and 2.7 billion years ago. Showing that the carbon in the soil is biological in origin and that it accumulated during soil formation is much more difficult. The researchers, who include Ohmoto; Yumiko Watanabe, Ph.D. candidate at Penn State and at Tohoku University, Sendai, Japan; and Jacques E. J. Martini, Geological Survey of South Africa, evaluated three possibilities for the formation of reduced carbon in the soil. The first of these was that the carbon was graphite crystals created when the underlying serpentine formed under high temperatures. The graphite then was concentrated during the soil formation. "The crystallinity and hydrogen/carbon rations of the organic matter suggest it is not of igneous or hydrothermal origin," says Ohmoto, a faculty member in Penn State's College of Earth and Mineral Sciences. The second possible origin of reduced carbon is liquid hydrocarbons introduced after the soil formation ended. Materials introduced after formation should show up along fractures in the rocks. "The organic matter is almost always concentrated in clay-rich parts of the rocks paralleling the ancient surface," says Ohmoto. "Organic matter and clays are so intimately mixed together that the size and morphology of individual 'grains' of organic mater can only be recognized under electron microscopes." The Penn State researchers conclude that the reduced carbon was not produced by high heat and then incorporated into the soil as it formed, nor was it deposited after the soil formed by migrating petroleum. The third possibility is that the organic carbon represents remnants of biomats developed on the soil surface. The researchers found that the organic-rich clays in the upper portion of the paleosol appeared as seams between fine-grained and coarse- grained layers of quartz. "These features suggest that the organic matter in the uppermost soil zone is an indigenous remnant of microbial mats that developed on the surface of clay-rich soil during the rainy season," says Ohmoto. "The mats were blanketed by aerosol deposits laid down during the dry season." In the lower portion of the paleosol, things are less clear because the effects of seeping water and the dissolution and precipitation of materials suggest some decomposition. While identifying the organism in the microbial mats is difficult, the researchers are certain that they were not photosynthetic sulfur bacteria as there is no sulfur present. Photosynthetic blue-green algae [cyanobacteria], however, are a likely possibility for the mat formation because the ancient remnants have nearly identical carbon isotope ratios as modern blue- green algal mats in fresh water. The researchers are also certain that the mats formed on land, not in the oceans, because the carbon isotope values for the carbon in the paleosol are distinctly different from the organic carbon found in marine sedimentary rock. "Although terrestrial bacterial communities were predicted by previous researchers, this is, to our knowledge, the first study presenting several lines of evidence for an extensive development of microbial mats on soil surfaces in the Archaean," says Ohmoto. "Our finding may then imply that an ozone shield developed before 2.6 billion years ago. "The ozone shield would have protected land-based biological forms from the effects of cosmic radiation. Development of the ozone shield requires an oxygen-rich atmosphere. Our finding of ancient biomats on land is an important addition to a growing line of evidence suggesting that the rise of atmopsheric oxygen took place more than 2.6 billion years ago." The University receives research funding for this and other efforts through the NASA Astrobiology Institute, a research consortium of academic, non-profit and NASA centers including Penn State. NASA's Ames Research Center is the agency's lead center for astrobiology, the study of the origin, evolution, dissemination and future of life in the universe. Contacts: A'ndrea Elyse Messer, (814) 865-9481(o), aem1@psu.edu Vicki Fong, (814) 865-9481(o), vfong@psu.edu Dr. Ohmoto is at (814) 865-4074 or at ohmoto@geosc.psu.edu by email. --------------------------------------------------------------------- ASTROBIOLOGISTS FIND EVIDENCE OF EARLY LIFE ON LAND NASA Ames release 00-79AR 29 November 2000 Scientists with NASA's Astrobiology Institute (NAI) have discovered fossilized remnants of microbial mats that developed on land between 2.6 billion and 2.7 billion years ago in the Eastern Transvaal district of South Africa. This significant discovery presents the strongest evidence to date that life on land occurred at a much earlier stage in Earth's history than was previously believed by most scientists. It also suggests that an ozone shield and an oxygen-rich atmosphere existed on Earth 2.6 billion years ago, both necessary conditions for life on land to emerge. The results are reported in the November 30 issue of Nature magazine. "This important investigation undertaken by an NAI team feeds into NASA's strategy of using Earth analogs, particularly analogs present on early Earth, as models for testing the hypothesis that life exists, or has existed, on Mars or elsewhere in the universe," said Dr. Baruch Blumberg (Nobel '76), director of the NAI research consortium. "A major goal of the NAI is to undertake the basic science that is necessary for the performance of NASA and space science missions." The finding also has other important implications for NASA. "The suggestion that an ozone shield existed as early as 2.6 billion years ago boosts our chances in the search for life on planets orbiting other stars," said Dr. Michael Meyer, astrobiology discipline scientist at NASA Headquarters, Washington, DC. "Ozone would be easily detectable by the Terrestrial Planet Finder, a planned interferometer mission in NASA's 'Origins' program." The microbial mats discovered by researchers are composed primarily of cyanobacteria, the principal organisms that generate oxygen from water and atmospheric carbon dioxide using sunlight. "This discovery is similar to what scientists went through with marine organisms," said Dr. Hiroshi Ohmoto, co-author of the Nature report, a member of the NAI, director of the Astrobiology Research Center and a faculty member in the Department of Geosciences at The Pennsylvania State University. "Once scientists thought no living organisms existed in the Earth's oceans before 500 million years ago. Then they studied the carbonaceous matter in ancient sedimentary rocks deposited in the oceans and found that organisms lived in the oceans at least 3.8 billion years ago," he said. A variety of geochemical and paleontological data suggests that microorganisms flourished in Earth's oceans at least 3.8 billion years ago, but researchers have been unable to agree on when microorganisms first colonized the land. The oldest undisputed remains of terrestrial organisms are currently 1.2 billion-year-old microfossils discovered in 1994 in Arizona by Dr. Paul Knauth, a member of the NAI-Arizona State University astrobiology team. However, many scientists think the Earth's land surface was sterile until about 500 million years ago, when vesicular plants first appeared. Ohmoto noted that the organic matter found in South Africa occurred primarily as parallel seams in the ancient 2.6 billion-year-old soil bed. This suggests that the organic seams are remnants of biomats that developed on the soil surface and were trapped while the soil formed. The team discovered the "right" ratios of chemical elements essential for life (carbon, hydrogen, nitrogen and phosphorous) in the carbonaceous matter of the Eastern Transvaal. This provides strong evidence that the carbonaceous matter is of biological rather than abiotic origin, according to Ohmoto. The Pennsylvania State University is a member of, and receives research funding for this and other efforts through, NASA's Astrobiology Institute, a research consortium encompassing academic and non-profit organizations plus NASA field centers. The NAI's central administrative office is located at NASA's Ames Research Center in California's Silicon Valley. In addition to full members, the NAI has international affiliate and associate members. Astrobiology is the study of the origin, evolution, dissemination and future of life in the universe. NASA's exobiology program also funded the subject research. Yumiko Watanabe, senior author of the Nature article, is a doctoral student of Ohmoto's at The Pennsylvania State University. Dr. Jacques Martini, another co-author, is a member of the Geological Survey of South Africa in Pretoria, and an associate member of The Pennsylvania State University Astrobiology Research Center. Contact: Kathleen Burton NASA Ames Research Center, Moffett Field, CA Phone: 650-604-1731 kburton@mail.arc.nasa.gov An additional article on this subject is available at http://www.spacedaily.com/news/life-00zx.html. --------------------------------------------------------------------- LUNAR METEORITE AGES STRONGLY SUPPORT 'LUNAR CATACLYSM' By Lori Stiles University of Arizona release 30 November 2000 Lunar meteorite ages present new, strong evidence for the "lunar cataclysm," a 20-to-200 million-year episode of intense bombardment of the moon and the Earth at 3.9 billion years ago-when the first evidence of life appeared on Earth, planetary scientists report in the December 1 issue of Science. Whether or not there was life on Earth at the beginning of the bombardment, such cataclysmic pounding would have enormous consequences for life on this planet, whether by destroying existing life or organic fragments or by delivering molecules and creating conditions suitable for life, the researchers add. Barbara Cohen of the University of Tennessee-Knoxville analyzed the lunar meteorite ages for her dissertation research at the University of Arizona in Tucson. Timothy D. Swindle and David A. Kring of the UA collaborated on the study and are co-authors on the Science article. Swindle supervised Cohen's research. Kring is an expert in impact cratering and one of the discoverers of the K/T boundary Chicxulub impact site. Moon rocks returned by the Apollo and Luna missions in the 1970s suggested that Earth's moon was blasted in a maelstrom of solar system debris at 3.9 billion years ago. A great swarm of asteroids or comets pounded the lunar surface during a brief pulse in geologic time, melting rocks, excavating vast craters and resurfacing Earth's natural satellite. But for safety and communications reasons, both manned and robotic spacecraft were landed near the moon's equator, on the side facing Earth. No one could say if just this part of the moon or the entire moon had been hammered. Cohen, Swindle and Kring bring the most significant data in nearly 30 years to bear on this question. They used an argon-argon dating technique in analyzing impact melt ages of four lunar meteorites- rocks ejected at random from the moon's surface and that landed on Earth after a million or so years in space. They find from the ages of the "clasts," or melted rock fragments, in the breccia meteorites that the entire moon was bombarded 3.9 billion years ago, a true global lunar cataclysm. Further, although the moon may have been bombarded before 3.9 billion years ago, the scientists find no evidence for it. If there were no earlier bombardment, scientists must jettison theoretical models that assume a steady falloff in the lunar and inner solar system cratering rate through time. "Given the model of what was going on in the solar system, there is no obvious reason why you should suddenly have a bunch of things banging on the moon 4 billion years ago and not 4.2 billion years ago," Swindle said. But the most dramatic implication is what happened during this event on Earth. "The Earth is a much bigger target than the moon, " said Kring, associate professor at the UA Lunar and Planetary Lab. "Earth would have been bombarded by at least 10 times as many impact events as the moon, and these impact cratering processes are immense. The Chixculub crater that we identified, which is related to the mass extinction of dinosaurs and other life 65 million years ago, is puny by comparison to the scheme we are talking about. Here we are talking about impacts that are 10 times larger, impacts that blasted craters rim-to-rim the size of continents on Earth today." "The bombardment would have charged the atmosphere with silicate vapor and vaporized the oceans, so if there was life on Earth before the bombardment, the question is what, if anything, survived," Swindle said. Perhaps some genetically primitive "extremeophiles" survived, he added. This kind of life is found on Earth today deep in rocks or living at the ocean vents. What did the bombarding? More likely asteroids than comets, based on some evidence from meteoritic trace constituents involved in the impacts and on other studies on what was happening at the time in the asteroid belt, Kring suggests. "When we first started this research, the goal was to find something older than 3.9 billion years," Cohen said. "We were very surprised at the evidence presented by seven different impacts, which pointed to 3.9 billion years." Swindle said, "Going into this study, I would have bet that we wouldn't have found these results. I would have bet that we would have seen impacts earlier than 3.9 billion years ago." Kring said, "I've quit being surprised at what impact cratering processes can do." Kring, director of the Lunar and Planetary Lab's Space Imagery Center, has just added new web pages on impact cratering, the lunar cataclysm and origin of life, the moon and lunar meteorites at the Space Imagery Center web sites. Related links http://www.lpl.arizona.edu/SIC/impact_cratering/intro/ http://www.lpl.arizona.edu/SIC/impact_cratering/lunar_cataclysm/ http://www.lpl.arizona.edu/SIC/impact_cratering/origin_of_life http://www.lpl.arizona.edu/SIC/moon/ http://www.lpl.arizona.edu/SIC/moon/lunar_meteorites/ Image captions http://uanews.opi.arizona.edu/cgi- bin/WebObjects/UANews.woa/wa/SRStoryDetails?ArticleID=2732 [Image 1] The moon's crater, Tycho, taken with NASA's Lunar Orbiter 5 spacecraft medium-resolution camera (1966-67). [Image 2] Barbara Cohen holds chips of meteorites DaG262 and DaG400 used in the analysis. [Image 3] David A. Kring. [Image 4] Timothy D. Swindle. Contacts: Barbara Cohen (UT), 865-974-6024, bcohen@utk.edu Timothy D. Swindle (UA), 520-626-5741, tswindle@lpl.arizona.edu David A. Kring (UA), 520-621-2024, kring@lpl.arizona.edu Bill Dockery, UT News Services, 865-974-2225, dockerb@utk.edu, is also a media contact on this story. --------------------------------------------------------------------- DRIED-UP SEA BEDS FOUND ON MARS By Jonathan Leake From The Sunday Times 3 December 2000 NASA scientists have discovered ancient sea or lake beds on the surface of Mars that could once have harbored life... The discovery is among the most significant concerning Mars so far, because such places are the most likely locations for fossils or other signs of past life. NASA will announce the discovery in this week's edition of Science with the suggestion that the next generation of Mars landings should be sent to such areas... ...The NASA discovery is based on images taken by Mars Global Surveyor, which has been orbiting the red planet for more than a year. It is said to have sent back detailed pictures of rocks that could only have been created by sedimentation, in which particles sink to a seabed and are compressed into rock. Get the full story at http://www.sunday- times.co.uk/news/pages/sti/2000/12/03/stifgnnws01001.html. An additional article on this subject is available at http://www.cnn.com/2000/TECH/space/12/01/mars.surprise/. --------------------------------------------------------------------- NEW ADDITIONS TO THE ASTROBIOLOGY, EXTREME ENVIRONMENTS AND TERRAFORMATION INDEX By David J. Thomas http://www.lyon.edu/webdata/users/dthomas/astrobiology/astrobiology.h tml 4 December 2000 Articles about astrobiology, exobiology and terraformation http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s1.html G. Arrhenius and S. Mojzsis, 1996. Extraterrestrial life: life on Mars-then and now. Current Biology, 6(10):1213-1216. F. B. Frankel and P. R. Buseck, 2000. Magnetite biomineralization and ancient life on Mars. Current Opinion in Chemical Biology, 4(2):171-176. Articles about the biology of extreme environments (on Earth) http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s2.html J. Jouzel, J. R. Petit, R. Souchez, N. I. Barkov, V. Y. Lipenkov, D. Raynaud, M. Stievenard, N. I. Vassiliev, V. Verbeke and F. Vimeux, 1999. More than 200 meters of lake ice above subglacial Lake Vostok, Antarctica. Science, 286(5447):2138-2141. J. C. Priscu, C. H. Fritsen, E. E. Adams, S. J. Giovannoni, H. W. Paerl, C. P. McKay, P. T. Doran, D. A. Gordon, B. D. Lanoil and J. L. Pinckney, 1998. Perennial Antarctic lake ice: an oasis for life in a polar desert. Science, 280(5372):2095-2098. Articles about human space exploration and the microgravity environment http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s3.html G. Obe, R. Facius, G. Reitz, I. Johannes and C. Johannes, 1999. Manned missions to Mars and chromosome damage. International Journal of Radiation Biology, 75(4):429-433. Articles about primordial evolution and prebiotic chemistry http://www.lyon.edu/webdata/users/dthomas/astrobiology/online_article s5.html J. R. Cronin and S. Pizzarello, 1997. Enantiomeric excesses in meteoritic amino acids. Science, 275(5302):951-955. SpaceDaily, 2000. Astrobiologists find evidence of early ground hoggers. SpaceDaily. --------------------------------------------------------------------- CASSINI WEEKLY SIGNIFICANT EVENTS JPL release 21-29 November 2000 The most recent spacecraft telemetry was acquired from the Madrid tracking station on Wednesday, November 29. The Cassini spacecraft is in an excellent state of health and is operating normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page at http://www.jpl.nasa.gov/cassini/english/where/. Activities this week included the completion of the third and start of the fourth of four instances of the Phase B 5-Day repeating template for Jupiter observations. Template activities include the Imaging Science Subsystem (ISS) 2x2 movie, Composite Infrared Spectrometer (CIRS) North / South Scans, ISS 1x4 Satellite Search, Cassini Plasma Spectrometer (CAPS) orientation to place -X axis to sun and rotate, and Radio and Plasma Wave Science (RPWS) calibration. Additional activities include reaction wheel momentum unloads, Radio Science (RS) Ultra Stable Oscillator (USO) calibration, uplink and execution of the Magnetospheric Imaging Instrument (MIMI) turn ON mini-sequence, CIRS Instrument Expanded Block load for C23 Phases C, D and E, and a Cosmic Dust Analyzer (CDA) threshold adjustment Instrument Operations (IO) and the Multi-Mission Image Processing Laboratory (MIPL) delivered 3825 ISS images and 33 Visual and Infrared Mapping Spectrometer (VIMS) cubes last week making a total of 9030 Jupiter images and 53 cubes delivered through 11/29. IO issued a report this week on the results of the in-flight test of the new VIMS Flight Software. Upgrades to the software were introduced to support Jupiter activities and are working as expected. IO-RS conducted a USO characterization. Ka- and X-band open and closed- loop data were obtained for four hours over DSS-25 at Goldstone, California. The new Radio Science Receiver was also used to acquire open-loop data. Data analysis is ongoing. An Atmosphere Working Group (AWG) telecon was held to begin the discussion of Saturn atmospheric science observations in the tour. This meeting went well with each Instrument Team interested in Saturn science discussing their plans for acquiring Saturn atmosphere science throughout the tour. A follow-up telecon has been scheduled for January. Mission Support & Services Office (MSSO) personnel participated in a cross-office meeting to coordinate the installation of Multi-Mission Spacecraft Analysis Subsystem (MSAS) V5.2 software for the Spacecraft Office (SCO). The software is to be installed on four workstations to test performance and use. Testing of the HP V25.2 is now complete. This software is to be installed on Navigation workstations. Cassini/Multi-Mission Ground Data System (CAS/MMGDS) training will begin in early December for new SCO, IO, Uplink Operations (ULO), and Science Planning (SP) personnel. A presentation on Cassini, with special attention on Jupiter results, was well-received last week at the Reuben H. Fleet Science Center in San Diego. University of California San Diego TV recorded the session for future broadcast. 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. --------------------------------------------------------------------- NASA'S MARS GLOBAL SURVEYOR SPIES FROSTY CRATERS JPL image advisory 27 November 2000 NASA's Mars Global Surveyor camera recently captured four wide-angle pictures of craters in both the northern and southern middle and polar latitudes of Mars that demonstrate how the camera is used to monitor changes in martian weather and the seasonal coming and going of polar frost. It is spring in the Northern Hemisphere, and frost that accumulated during the most recent six-month-long winter has been retreating since May. Examples of frost-rimmed craters include Lomonosov and an unnamed crater farther north. It is autumn in the Southern Hemisphere, and frost was seen as early as August in some craters, such as Barnard; later the frost line moved farther north, and frost began to appear in Lowell Crater in mid-October. The images are available at: http://photojournal.jpl.nasa.gov http://mars.jpl.nasa.gov/mgs http://www.msss.com/mars_images/moc/nov_00_craters/ Mars Global Surveyor is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA. JPL is a division of the California Institute of Technology in Pasadena. Malin Space Science Systems, San Diego, built and operates the camera system. JPL's industrial partner is Lockheed Martin Astronautics, Denver, which developed and operates the spacecraft. Additional articles on this subject are available at: http://spaceflightnow.com/news/n0011/28mgscraters/ http://www.msnbc.com/news/463318.asp --------------------------------------------------------------------- STARDUST STATUS REPORT JPL release 1 December 2000 The Stardust spacecraft and all subsystems are performing normally in cruise sequence SC024. The Navigation Camera's charge-coupled device and mirror motor heaters were turned on in a continuing effort to improve camera performance. An image of the calibration lamp was transmitted to Earth, showing that the camera continues to improve. With both heaters on, the temperatures of the CCD and mirror motor are already a few degrees higher than the previous heating cycle and are expected to rise even a few more degrees when trajectory correction maneuver #4 (TCM-4) is performed, since the inertial measurement unit is on and the sun will be shining on the Navigation Camera radiator. These heaters will be turned off later in December before trajectory correction maneuver #5 (TCM-5). All processes are proceeding well in preparation for Earth Gravity Assist (EGA.) The trajectory correction maneuver that was planned for this week has been moved to next week. A larger than desired error accumulated in the calculated maneuver due to erroneous small forces data obtained while in safe mode last week. This error could have been taken out in TCM-5; however it was decided to remove this error in TCM-4. An additional benefit was gained by combining TCM-4 with the spacecraft turn to EGA flyby attitude all in one sequence next week rather than 2 sequences if we implemented TCM-4 this week and then the turn to EGA attitude next week. 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 7, Number 46.