MARSBUGS: The Electronic Exobiology Newsletter Volume 4, Number 6, 7th May, 1997. Editors: David Thomas, Department of Biological Sciences, University of Idaho, Moscow, ID, 83844-3051, USA, thoma457@uidaho.edu or Marsbugs@aol.com. Julian Hiscox, Division of Molecular Biology, IAH Compton Laboratory, Compton, Nr. Newbury, Berkshire RG20 7NN, UK. Julian. Hiscox@bbsrc.ac.uk or marsbug@msn.com 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. E-mail subscriptions are free, and may be obtained by contacting either of the editors. 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 may be obtained via anonymous FTP at: ftp.uidaho.edu/pub/mmbb/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. Exobiology is still a relatively young field, and new ideas may come out of the most unexpected places. Subjects may include, but are not limited to: exobiology proper (life on other planets), the search for extraterrestrial intelligence (SETI), ecopoeisis/ terraformation, Earth from space, planetary biology, primordial evolution, space physiology, biological life support systems, and human habitation of space and other planets. ----------------------------------------------------------------- INDEX 1) MARS PATHFINDER PASSES GLOBAL SURVEYOR ON ITS WAY TO MARS JPL release 2) MARS GLOBAL SURVEYOR TO AEROBRAKE IN MODIFIED CONFIGURATION NASA release: 97-85 3) LIFE (?) IN MARTIAN METEORITE ALH 84001: A PREVIEW OF PRESENTATIONS AT THE UPCOMING 28TH LUNAR AND PLANETARY SCIENCE CONFERENCE Lunar and Planetary Institute 4) METEORITE STUDY SHOWS GLIMPSE OF RED PLANET'S ANCESTRY From Purdue News 5) CALTECH GEOLOGISTS FIND NEW EVIDENCE THAT MARTIAN METEORITE COULD HAVE HARBORED LIFE California Institute of Technology 6) EUROPA: IS THERE LIFE UNDER ICE? Voice of America Transcript. ----------------------------------------------------------------- MARS PATHFINDER PASSES GLOBAL SURVEYOR ON ITS WAY TO MARS JPL release March 14, 1997 Like two ships passing in the night, NASA's Mars Pathfinder spacecraft will begin to overtake Mars Global Surveyor tonight, moving closer to Mars than its companion orbiter and closing in for the final four-month approach to the red planet. Mars Pathfinder, a lander carrying a small rover and science instruments to Mars, has less than half of its total distance to complete now, said Dr. Robin Vaughan, Pathfinder navigation team member at NASA's Jet Propulsion Laboratory. The spacecraft will overtake Mars Global Surveyor at 0100 Universal Time on March 15 (5 p.m. Pacific Standard Time tonight, March 14). At the time of the event, Mars Pathfinder will be 43.7 million kilometers (27 million miles) from Earth and 69.7 million kilometers (43.2 million miles) from Mars. The spacecraft is more than halfway along its arcing flight path, on which it will have traveled a total of 497 million kilometers (309 million miles) by the time it reaches Mars. "Although Pathfinder was launched about a month after Mars Global Surveyor, it is traveling faster than Surveyor and is on a shorter flight path to the red planet," said Brian Muirhead, Pathfinder project manager at JPL. "Whereas Mars Global Surveyor will take 10 months to reach Mars, Pathfinder takes only seven months. Once we reach Mars, we dive directly into the Martian atmosphere. The descent will only take about four minutes, and we should be on the surface of Mars by about 10 a.m. Pacific time on July 4th." Pathfinder is on a different type of trajectory to Mars than Mars Global Surveyor. Called a "Type 1" trajectory, the spacecraft does not have to travel as far to intercept Mars. Mars Global Surveyor will log a total of 700 million kilometers (435 million miles) in its flight path toward the red planet. "The advantage to using a Type 1 trajectory is that you have to travel less than one-half of the way around the Sun to intercept Mars," Vaughan said. "So Pathfinder takes 212 days to reach Mars, while Mars Global Surveyor will spend 309 days to reach the planet." Mars Global Surveyor is on a "Type 2" trajectory, taking it more than 180 degrees around the Sun to intercept the planet. A major difference in this type of trajectory is that the spacecraft travels at a slower velocity with respect to the Sun. Subsequently, the craft requires less fuel to slow down at Mars than if it had followed Pathfinder's trajectory. For instance, Pathfinder is currently traveling at 27 kilometers per second (60,700 miles per hour), while Mars Global Surveyor is traveling at about 26.75 kilometers per second (59,800 miles per hour). "Less fuel translates into simpler, smaller spacecraft and less expense," said Glenn Cunningham, Mars Global Surveyor project manager. "Mars Global Surveyor also will employ a fairly new technique requiring very little fuel to drop down into its mapping orbit. The technique is called 'aerobraking,' and takes advantage of the drag of the Martian atmosphere. As the spacecraft dips down into the top of the atmosphere at its closest point to the planet each orbit, the drag from the atmosphere on the spacecraft will reduce its orbital speed. This drops the altitude of the highest part of the orbit, changing it from the initial elliptical shape to the circular shape required for mapping the planet." Aerobraking was first demonstrated successfully with the Magellan spacecraft, which mapped the surface of cloud-covered Venus using a sophisticated radar-imaging system. Magellan aerobraked into the Venusian atmosphere in October 1994, sending back data about Venus' thick sulfur and carbon dioxide-choked atmosphere until it burned up in the planet's sizzling temperatures. Mars Global Surveyor, however, will not dip so far into the much thinner Martian atmosphere that it would burn up. Pathfinder is scheduled to perform two more flight path corrections and, possibly, a fifth maneuver to keep it on course for landing on Mars on July 4. The last two maneuvers will occur near the end of the cruise phase, on May 7 and June 24, when the spacecraft is close to Mars. If necessary, a fifth maneuver will be executed just a few hours before entry into the Martian atmosphere on July 4. Mars Global Surveyor will perform its second trajectory correction maneuver on March 20. Engineers are continuing to explore possible ways of freeing a broken damper arm that is wedged in the joint of one of the solar arrays, so that the panel locks in place. The Mars Pathfinder and Mars Global Surveyor missions are managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C. Pathfinder is the second in NASA's Discovery program of low-cost spacecraft designed to carry out highly focused science goals. Mars Global Surveyor is the first spacecraft in a decade-long program of robotic exploration, called the Mars Surveyor Program. ----------------------------------------------------------------- MARS GLOBAL SURVEYOR TO AEROBRAKE IN MODIFIED CONFIGURATION NASA release: 97-85 April 30, 1997 NASA's Mars Global Surveyor spacecraft can safely and successfully aerobrake into its final orbit around Mars this fall with its one partially deployed solar panel in a modified configuration, mission managers have decided. No special maneuvers will be conducted to attempt to force the array to latch, and the focus of the Surveyor engineering team now will turn to minor modifications to the critical aerobraking phase that will circularize the spacecraft's orbit for the beginning of two years of science operations. "After careful analysis of the situation, we've determined that the solar panel on Mars Global Surveyor that is not fully deployed presents very little risk to the mission," said Glenn E. Cunningham, Mars Global Surveyor project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. The decision by NASA's flight team at JPL and its partners at Lockheed Martin Astronautics, Denver, CO, was reached after several months of extensive analysis of spacecraft data, ground-based computer simulations and a series of very slight spacecraft maneuvers that were carried out in January and February to characterize the situation. "Thanks to an early launch that gave us an advantageous trajectory, we will not have to aerobrake into the Martian atmosphere as fast as we had originally planned to reach the mapping orbit, and that will reduce the amount of heating that the solar panels undergo during this gradual descent," Cunningham explained. "We will rotate the solar-cell side of the panel that is not fully deployed by 180 degrees, so that it faces into the direction of the air flow that exerts drag force on the spacecraft as it dips repeatedly into the atmosphere," he said. "This way, the unlatched panel will not be in danger of folding up onto the spacecraft's main structure, nor will the panel be at any greater risk of heating up too much." The solar panel in question is one of two 11-foot wings that were unfolded shortly after Surveyor's Nov. 7, 1996, launch from Cape Canaveral Air Station, FL. Data suggest that a piece of metal called the "damper arm," which is part of the solar array deployment mechanism located at the "elbow" joint where the entire panel is attached to the spacecraft body, probably was sheared off during deployment in the first day of flight. The lever that turns the shaft became wedged in a two-inch space between the shoulder joint and the edge of the solar panel, leaving the panel tilted at 20.5 degrees from its fully deployed and latched position. Although the situation was never considered a serious threat to accomplishing the science objectives of the mission, the tilted array caused the JPL/Lockheed Martin flight team to re-evaluate the aerobraking phase, in which the spacecraft must rely almost solely on its solar panels for the drag needed to lower it into a nearly circular mapping orbit over the poles of the planet. This phase of the mission will begin a week after Mars Global Surveyor is captured in orbit around Mars on Sept. 11, and will last approximately four months. Aerobraking was first tested in the final days of the Magellan mission to Venus in October 1994. The technique is an innovative method of braking which allows a spacecraft to carry less fuel to a planet and take advantage of the planet's atmospheric drag to descend into a low-altitude orbit. Mars Global Surveyor will use an aerobraking phase much like that used to circularize Magellan's orbit. The solar wings -- which feature a Kapton flap at the tip of each wing for added drag -- supply most of the surface area that will slow the spacecraft by a total of more than 2,684 miles per hour during the four-month phase. Surveyor's orbit around Mars will shrink during this phase from an initial, highly elliptical orbit of 45 hours to a nearly circular orbit taking less than two hours to complete. Engineers determined that the deployment springs currently holding the tilted solar panel in its nearly deployed position will not be strong enough to withstand the forces of aerobraking. To solve that problem, they designed a new configuration in which the tilted solar panel, along with the deployment springs, will be rotated 180 degrees, using a motor- driven inner gimbal actuator, and held in position with force applied by an outer gimbal actuator. Sequencing software will be modified to turn the gimbal actuators on before each closest approach to the planet and off at the conclusion of each drag pass. As a consequence of the new aerobraking configuration, the more sensitive cell-side of the unlatched wing will be exposed directly to the wind flow of atmospheric entry, requiring that aerobraking be done in a more gradual, gentle manner. Ground tests have demonstrated that the unlatched solar panel will have more than adequate thermal margin to withstand additional heating as the spacecraft circularizes its orbit for the beginning of science mapping in March 1998. Meanwhile, Mars Global Surveyor continues to perform very well on its arcing flight path toward the red planet and its arrival in orbit. A third, very minor trajectory correction maneuver, planned for April 21, was deemed unnecessary and canceled. In addition, science instrument calibrations continue to go well, and plans are being prepared to take an approach image of Mars a few days before the July 4 landing of Mars Pathfinder, which passed Mars Global Surveyor enroute to Mars on March 14, 1997. Mars Global Surveyor is the first mission in a sustained program of robotic exploration of Mars, managed by JPL for NASA's Office of Space Science, Washington, DC. ----------------------------------------------------------------- LIFE (?) IN MARTIAN METEORITE ALH 84001: A PREVIEW OF PRESENTATIONS AT THE UPCOMING 28TH LUNAR AND PLANETARY SCIENCE CONFERENCE Lunar and Planetary Institute [Editor's note: This conference has already come and gone, but I thought the readers might be interested in what was presented. DJT] The 28th Lunar and Planetary Conference, March 17-21 1997 (LPSC), will be the first major planetary science conference since Dr. D. McKay and co-workers announced the possible presence of traces of ancient martian life in the meteorite ALH 84001. The conference will be in Houston, Texas at the NASA Johnson Space Center (JSC) and the Lunar and Planetary Institute (LPI). At least 37 presentations of new research on the martian meteorite ALH 84001 will be given at the 28th LPSC. Abstracts of these works are listed below, in the order of presentation, with short descriptions of their contents. The abstracts are arranged in the order they will be presented. 1799 McKay G. A. and Lofgren G. E. Carbonates in ALH 84001: Evidence for kinetically controlled growth. The authors investigated chemical zoning in the carbonates of ALH 84001, and conclude that the carbonate grew rapidly into open spaces. Rapid growth permitted the carbonates to have their unusual compositions, without the need to call on unusual chemical or physical conditions. Besides the well-known carbonate occurrences as zoned pancakes and ellipsoids, the authors also describe carbonates as veins filling cracks and as pockets in orthopyroxene crystals. 1192 Treiman A. H. Chemical disequilibrium in carbonate minerals of martian meteorite ALH 84001: Evidence against high formation temperature. The author evaluated Harvey and McSween's (1996) arguments that the carbonates of ALH 84001 formed at high temperature, and found them all flawed. Their arguments for high temperature all assumed chemical equilibria among carbonate and silicate minerals in ALH 84001; mineral compositions and chemical theory suggest no chemical equilibria, so the inferences of high temperature are not valid. 1789 Scott E. R. D., Yamaguchi A., and Krot A. N. Shock melting of carbonate, plagioclase, and silica in the martian meteorite ALH 84001. From the textures and compositions of the carbonates and the surrounding feldspar-composition glass, the authors conclude that both formed at high temperature as shock melts. Micron-wide veinlets of feldspar-composition glass in pyroxene grains, and veinlets of this glass and carbonate minerals, suggest that all the shock effects in ALH 84001 all came from a single shock event, which must have melted both the feldspar and the carbonate and injected them into the pyroxene. 1842 Kirschvink J. L., Maine A., and Vali H. Paleomagnetic evidence supports a low-temperature origin of the carbonate in martian meteorite ALH 84001. The natural remnant magnetism is aligned differently in the carbonates and orthopyroxene of ALH 84001. This means that the carbonates and orthopyroxene could not have been hot at the same time; if they were both hot, their remnant magnetic fields would be aligned the same. From their sizes, shapes, and magnetic properties, the magnetite crystals in ALH 84001 must have formed at a temperature below 150 C. [In addition this work suggests that Mars had a strong magnetic field when the orthopyroxenes and carbonates formed; Mars now has very little, if any, magnetic field.] 1671 Greenwood J. P., Riciputi L. R., and McSween H. Y. Jr. Sulfur isotopic variations in sulfides from shergottites and ALH 84001 determined by ion microprobe: No evidence for life on Mars. The authors measured the relative abundances of sulfur isotopes in pyrite and carbonate rims in ALH 84001, and did not find the isotope ratios characteristic of sulfur-eating bacteria on Earth. These bacteria tend to use the lighter isotope of sulfur, so the bacteria's products are isotopically "light," with d34S much less than 0%. Sulfur in ALH 84001 pyrite is somewhat heavy, with d34S between +2.0 and +7.3% (as was found by Shearer et al., 1996). Sulfide in carbonate dark rims is not light either, with d34S = +6 +/- 6.7%. "The significant enrichments in 32S expected if the sulfides were products of sulfate-respiring bacteria... are not found." 1445 Valley J. W., Eiler J. M., Graham C. M., Gibson E. K. Jr., and Romanek C. S. Ion microprobe analysis of oxygen and carbon isotope ratios in the ALH 84001 meteorite. The authors analyzed oxygen and carbon isotope ratios in the carbonates (using ion microprobe). The oxygen had d18O from 9.5 to 20.6%, with two carbonate ellipsoids having different average d18Os. "The high values of d18O in Carb. #1 cannot represent isotopic equilibrium with the host orthopyroxene at temperatures above 100-200 C .... On Earth, such high and variable d18O is proof of low-temperature exchange because isotopic fractionations are small at high temperature." Carbon isotope ratios were mostly constant, but occasionally varied widely, suggesting the presence of an unidentified compound with very light carbon (d13C < -50%). 1657 Gilmour J. D., Lyon I. C., Saxton J. M., Turner G., and Whitby J. A. Oxygen and noble gas isotope constraints on the origin of ALH 84001 carbonate. Xenon isotope measurements again confirm the martian origin of ALH 84001; 129Xe/132Xe ratios range up to 2.4, which is current martian air. Oxygen isotope ratios for the carbonate globules are inconclusive for their formation temperature, although their oxygen isotopes must have been through some chemical processes at a low temperature. A relatively low value of the abundance ratio Cl/36Ar suggests that the carbonates formed at high temperature. 1544 Gibson E. K. Jr., McKay D. S., Thomas-Keprta K., Romanek C. S., Clemett S. J., and Zare R. N. Possible relic biogenic activity in martian meteorite ALH 84001: A current assessment. A review of potential biogenic features in ALH 84001, a review and guide to current work and abstracts on these features (especially biofilms), and an affirmation of the inferences of McKay et al. (1996). 1615 Westall F., de Wit M. J., and Dann J. What do fossil bacteria look like? Examples of 3.5-billion-year old mineral bacteria and the search for evidence of life in extraterrestrial rocks. For comparison with possible fossil bacteria in ALH 84001, the authors report on confirmed fossil bacteria from 3.5-billion-year-old cherts from Barberton, South Africa. These fossil bacteria are short rods, 0.65-1.0 m long; they appear individually, in clusters of identically sized cells, and as fossilized bacterial mats. The authors emphasize that these fossils have no remaining organic matter, and are preserved only as shaped mineral grains. So, potential fossils in ALH 84001 might be recognized only by size and shape, not organic material. 1345 Thomas-Keprta K. L., Wentworth S. J., McKay D. S., Stevens T. O., Golden D. C., Allen C. C., and Gibson E. K. Jr. The search for terrestrial nanobacteria as possible analogs for purported martian microfossils in the martian meteorite ALH 84001. Very small bacteria, nanobacteria, have been proposed as terrestrial analogs for the bacteria-shaped objects in ALH 84001. The authors investigate whether terrestrial nanobacteria occur in environments like those proposed for ALH 84001: lightless, with only the rock and water for sustenance. Basalt lava rocks beneath the Columbia River plateau (eastern Washington) have been affected by bacterial action, and the authors attempted to culture nanobacteria from these rocks in fresh basalt rock. After culturing, the basalt rocks contained small filaments and rounded shapes, on the order of 0.35 m long and 0.02 m wide. These sizes and shapes are comparable to those of potential microfossils in ALH 84001. 1681 Steele A., Goddard D. T., Stapleton D., Smith J., Tapper R., Grady M., McKay D. S., Gibson E. K., Thomas-Keprta K. L., and Beech I. B. Atomic force microscopy imaging of ALH 84001 fragments. Published images of possible bacteria shapes from ALH 84001 have been criticized as being artifacts of sample preparation. To study this possibility, the authors examined untreated, uncoated surfaces of carbonate globules using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM). ESEM was used to locate regions of the globules rich in magnetite and iron sulfides in these regions, AFM imaging showed that the globule surfaces were covered with rounded protrusions of 0.1 to 0.2 m diameter, and showed a single segmented structure 0.5 m long. The authors conclude that the bacteria shapes in earlier published images were real, and not products of sample preparation. 1413 Wright I. P., Grady M. M., and Pillinger C. T. An investigation into the association of organic compounds with carbonates in ALH 84001. By selectively dissolving carbonate globules in acid, the authors attempted to separate organic material and carbonate minerals for carbon isotope analyses. The experiment was a partial failure, as most of the carbon was lost during processing. The authors hypothesize that the lost carbonate material might have been mostly magnesite (which is intrinsically resistant to acid), or that its mineral grains might have been coated with acid-resistant biofilms. 1548 Flynn G. J., Keller L. P., Kirz J., Wirick S., Bajt S., and Chapman H. N. Carbon mapping and carbon-XANES measurements on carbonate globules in ALH 84001. Using an X-ray microscope and X-ray Absorption Near-Edge Structure (XANES) spectra, the authors have searched for organic carbon in the carbonate globules. Mapping of a small sample (analysis spot size only 0.05 m) showed many areas with 1% or more organic carbon. Work continues. 1455 Bishop J. L., Pieters C. M., and Hiroi T. Spectroscopic properties of martian meteorite ALH 84001 and identification of minerals and organic species. As an aid to mineral identification and application to Mars, the authors obtained visible and infrared reflection spectra of chips and powders of ALH 84001. All major mineral species (recognized by microscope) were detected in reflection spectroscopy. Some light absorption features in infrared light (3.3-3.5 m wavelength) are from organics, and are not always associated with the carbonates. 1810 Griffith L. L. and Shock E. L. Orthopyroxene hydrothermal alteration pathways: Low vs. high temperature. Using chemical equilibrium modeling, the authors investigate whether it would be possible for the carbonate globules in ALH 84001 to form at low temperature without also forming clays and other water-bearing silicates. In fact, the authors find that orthopyroxene (as in ALH 84001) can react with carbonated water at ~75 C to yield magnesite and quartz without clays, talc, or other water-bearing minerals. So, the absence of water-bearing minerals with the ALH 84001 carbonates is not proof that they formed at high temperature. 1687 Steele A., Goddard D. T., Grimes G. W., Stapleton D., Smith J., Tapper R., Grady M., McKay D. S., Gibson E. K., Thomas-Keprta K. L., and Beech I. B. Scanning proton microprobe imaging of ALH 84001 fragments. The authors applied proton microprobe imaging to examine the three-dimensional distribution of carbon and other elements in ALH 84001 carbonate globules. Preliminary results are consistent with element distribution maps from other methods. 1675 Golden D. C., Thomas-Keprta K. L., McKay D. S., Wentworth S. J., Vali H., and Ming D. W. Size distribution of magnetite in carbonate globules of ALH 84001 martian meteorite. Using transmission electron microscopy, the authors measured the sizes of many magnetite grains from the carbonate globules. The magnetite crystals, from both cores and rims of globules, were mostly cubes and octahedrons; no ribbons or whiskers were observed. These ALH 84001 magnetites are similar in sizes and shapes to those deposited by a common strain of bacteria on Earth, and so are consistent with a biogenic origin. 1224 Flynn G. J., Sutton S., and Keller L. P. Element abundance patterns in carbonate globules and rims from ALH 84001. To understand the formation temperature of the carbonate globules, the authors analyzed carbonate chips for many trace elements using analytical X-ray microscopy. Many elements are distributed irregularly; abundances of S, Cl, and Br vary by approximately an order of magnitude. Average element/iron abundance ratios are nearly constant, suggesting that the globule rims formed in place by alteration of material like core carbonate. The chlorine/bromine ratio is always much higher than in Antarctic ice, suggesting little Antarctic contamination. The low abundances of volatile elements may suggest that the carbonate globules formed at high temperature. 1259 Allen C. C., Thomas-Keprta K. L., McKay D. S., and Chafetz H. S. Nanobacteria in carbonates. Using scanning and transmission electron microscopy, the authors looked for nanobacteria (like those hypothesized for ALH 84001) in carbonate mineral deposits from a hot spring. Mineral grains from the hot spring were found to be coated with thin layers of "mucus," a biofilm. In the film are spheroids of 0.05 to 0.5 m diameter, similar in size to the possible fossil bacteria in ALH 84001. It is not yet clear if the spheroids are fossil bacteria or abiogenic mineral deposits. 1661 Barlow N. G. The search for possible source craters for martian meteorite ALH 84001. ALH 84001 was ejected from Mars ~16 million years ago by an asteroid impact. The impact crater source of ALH 84001 is not known; two young craters in ancient highlands, eroded by water, are suggested as the most likely candidates. 1817 McKay D. S., Gibson E. K., Thomas-Keprta K., Romanek C. S., and Allen C. C. Possible biofilms in ALH 84001. Bacteria on Earth commonly produce thin films of organic polymers, so-called biofilms. The authors searched fragments of ALH 84001 for these biofilms. On lightly etched surfaces of carbonate and silicates from ALH 84001, the authors observed films of material that appear similar to terrestrial biofilms. The films do not appear to be clays, but are otherwise uncharacterized. The physical association of the films with martian carbonate materials suggests to the authors that the films are also martian. ____________________________________________ 1545 Bradley J. P., Harvey R. P., and McSween H. Y. Jr. Magnetite whiskers and platelets in the ALH84001 martian meteorite: Evidence of vapor phase growth. Using transmission electron microscopy, the authors found tiny magnetite crystals, whiskers and ribbons ~0.05 m long, in the carbonate globules. These magnetite crystals are similar to crystals that grow at high temperature from a vapor, and are unlike magnetite crystals formed by bacteria. The authors also found a group of aligned magnetite whiskers that looks like one published image of potential fossil bacteria in ALH 84001; could these potential fossil bacteria be aligned magnetite crystals? 1461 Thomas-Keprta K. L., Romanek C. S., Wentworth S. J., McKay D. S., Fisler D., Golden D. C., and Gibson E. K. TEM analysis of fine-grained minerals in the carbonate globules of martian meteorite ALH 84001. Using transmission electron microscopy, the authors examined minerals and structures in the carbonate globules, especially in the dark rim zones. Their work confirms earlier findings of magnetite (iron oxide) and pyrrhotite (iron sulfide) in a porous carbonate matrix. The authors also found a few patches of clay minerals in the orthopyroxene; this is the first report of water-bearing minerals in ALH 84001. Finally, the authors dispute Bradley et al.'s (1996, 1997) claims that that magnetite crystals shaped like whiskers or ribbons must have formed at high temperature by citing references to similar magnetite crystals formed by Earth bacteria. 1235 Shearer C. and Papike J. J. The petrogenetic relationship between carbonates and pyrite in martian meteorite ALH 84001. The authors are concerned with whether the carbonates and pyrite in ALH 84001 formed together, because their earlier sulfur isotope studies of the pyrite showed no sign of biologic processes. Their textural and chemical analyses suggest that the carbonate globules grew from a water-rich solution at low temperature, that the earliest carbonates could have formed from the orthopyroxene, and that the pyrite may have formed at the same time as the early carbonates. 1399 Leshin L. A., McKeegan K. D., and Harvey R. P. Oxygen isotopic constraints on the genesis of carbonates from martian meteorite ALH 84001. To test Romanek et al.'s (1994) inference that the carbonates formed at low temperature, the authors analyzed the oxygen isotopic composition of the carbonates by ion microprobe. They found that the carbonates had a wide range of oxygen isotope compositions, measured as d18O from +5.6% to +21.6%, a much wider range than Romanek et al. found. Many of the analyses, those with d18O = +5.6 to +8.5% are consistent with high-temperature equilibration of oxygen isotopes with the surrounding silicates, so the authors favor a high-temperature origin. 1820 Vali H., Zhang C., Sears S. K., Lin S., Phelps T. J., Cole D., Onstott T. C., Kirschvink J. L., Williams-Jones A. E., and McKay D. S. Formation of magnetite and Fe-rich carbonates by thermophilic bacteria from deep terrestrial subsurface: A possible mechanism for biomineralization in ALH 84001. The authors searched for, and found, a bacterial system on Earth that would produce the same minerals (magnetite and Fe-rich carbonates) as in the carbonate globules of ALH 84001. They incubated bacteria from deep rock strata with amorphous iron and various "foods" (like glucose or acetate). The bacteria grew and deposited small magnetite crystals of sizes and shapes like those found in ALH 84001. When conditions were alkaline and rich in carbon dioxide, the bacteria also deposited crystals of iron carbonate (siderite), as is found in ALH 84001. 1264 Hua X. and Buseck P. R. Magnetite in carbonaceous chondrites. For comparison with magnetites in ALH 84001, the authors describe the shapes and compositions of magnetites in the carbonaceous chondrite meteorites, which contain carbon compounds that were produced without life. Carbonaceous chondrites contain many varieties of magnetite, and work is continuing on magnetites that are the same sizes as those in ALH 84001. 1530 Browning L. B. and Bourcier W. L. Did the porous carbonate regions in ALH 84001 form by low temperature inorganic processes? McKay et al. (1996) identified porous areas of ALH 84001 carbonates with magnetite and greigite(?) crystals as probably biogenic in origin. The authors here suggest some inorganic mechanisms for formation of the porous areas, and note again that the absence of clay minerals seems inconsistent with a low-temperature origin for the carbonate globules. 1554 Eiler J., Valley J. W., and Graham C. M. Standardization of SIMS analyses of O and C isotope ratios in carbonates from ALH 84001. Companion paper to Valley et al., describing their analytical methods. Ion microprobe analyses for O and C isotope ratios in carbonate minerals are very sensitive to the compositions of the minerals. To get real isotope ratios, they had to calibrate and correct for this sensitivity. 1411 Kurat G., Hoppe P., Brandstaetter F., and Koeberl C. Fluid precipitation of chromite and feldspar-rich glass in martian orthopyroxenite ALH 84001. Paired with the following abstract. Based on analyses of mineral compositions, they suggest that most of the rarer minerals in ALH 84001 (chromite, feldspar glass, apatite) were deposited by "fluids," not magma. Neither the composition nor temperature of the fluids are specified. 1415 Kurat G., Nazarov M. A., Brandstaetter F., Ntaflos T., and Koeberl C. Precipitation and reaction products of fluids in martian orthopyroxenite ALH 84001. Paired with the preceding abstract. They infer a complex history, including deposition of chromite and feldspar-rich glass from a CO2-rich aqueous fluid. 1859 Rice J. W. Jr. Searching for the ALH 84001 "smoking gun" (parent crater). The author lists the 19 youngest craters on ancient (Noachian) areas of Mars; among these, he suggests that the source crater of ALH 84001 is probably in Memnonia at 5 S, 146 W. 1222 Shearer C. K. Sulfur isotopic systematics in ALH 84001. Open- and closed-system behavior of sulfur in a martian hydrothermal system. An attempt to model earlier analyses of sulfur isotopes in ALH 84001 pyrite if it were formed by bacterial activity (with metabolism like Earth bacteria), at low temperature (McKay et al., 1996), and from starting materials with a sulfur isotope composition like common basalts (and the other martian meteorites; Greenwood et al.,). The observed isotope composition cannot be modeled by bacterial growth with any water flow rate or starting material, so he concludes that either "the pyrite did not the precipitate during biogenic activity," or "the solutions precipitating carbonate and pyrite were highly enriched in the heavy sulfur isotope." 1433 Treiman A. H. Thinking about life on Mars: Dangers and visions. Many of the commonly accepted norms of Earth life (including cell division, standard biochemical pathways, and homochirality) are not followed in all Earth organisms. With so much intrinsic variability in Earth life, it is dangerous to extrapolate from the Earth norm to martian life. 1414 Wright I. P., Grady M. M., and Pillinger C. T. Isotopically light carbon in ALH 84001: Martian metabolism or Teflon contamination? In October, these authors reported finding organic matter in ALH 84001 that was strongly enriched in the light isotope of carbon, d13C >> -60%, which was widely reported as "proof" of biogenic activity. The interpretation of this isotopically light carbon is not clear. The light carbon was released from the samples at temperatures consistent with it being from carbonate mineral, not organic material. However, no analyses of carbonate carbon have give such low d13C. Teflon does behave like this isotopically light carbon in ALH 84001, and has a comparably low d13C. For the light carbon to be from Teflon, the whole analyzed sample would have to have been 45% Teflon, which the authors doubt. 1601 Wright I. P., Grady M. M., and Pillinger C. T. Evidence relevant to the life on Mars debate. (1) 14C results. The martian meteorite EETA 79001 (NOT the subject of the recent "life on Mars" articles) contains carbonate minerals that formed at low temperatures, but analyses of 14C (carbon 14) in the carbonates had suggested that they formed recently on Earth. The authors dispute this interpretation, arguing that the observed 14C is a minor component added to original martian carbonates. Thus the organic material associated with the EETA 79001 carbonates is also martian. 1602 Wright I. P., Grady M. M., and Pillinger C.T. Evidence relevant to the life on Mars debate. (2) Amino acid results. The martian meteorite EETA 79001 (NOT the subject of the recent "life on Mars" articles) contains amino acids similar to those of terrestrial life, and was interpreted earlier as having entered the meteorite while it was in Antarctica. The authors dispute this view, and claim that the amino acids in EETA 79001 are too abundant to have come from Antarctic ice or meltwater. In addition, the "left-handed-ness" of the EETA79001 amino acids could represent not only terrestrial biological contamination, but also amino acids produced inorganically by a number of processes, or even martian biological "contamination." References: Bradley J. P., Harvey R. P., and McSween H. Y. Jr. (1997) Magnetite whiskers and platelets in ALH 84001 Martian meteorite: Evidence of vapor phase growth. Geochim. Cosmochim. Acta, 60, 5149-5155. Harvey R.P. and McSween H.Y. Jr. (1996) A possible high-temperature origin for the carbonates in the martian meteorite ALH84001. Nature, 382, 49-51. McKay D. S., Gibson E. K. Jr., Thomas-Keprta K. L., Vali H., Romanek C. S., Clemett S. J., Chillier X. D. F., Maechling C. R., and Zare R. N. (1996) Search for past life on Mars: Possible relic biogenic activity in martian meteorite ALH 84001. Science, 273, 924-930. Romanek C. S., Grady M. M., Wright I. P., Mittlefehldt D. W., Socki R. A., Pillinger C. T., and Gibson E. K. Jr. (1994) Record of fluid-rock interactions on Mars from the meteorite ALH 84001. Nature, 372, 655-657. Shearer C. K., Layne G. D., Papike J. J. and Spilde M. N. (1996) Sulfur isotope systematics in alteration assemblages in martian meteorite ALH 84001. Geochim. Cosmochim. Acta, 60, 2921-2926. ----------------------------------------------------------------- METEORITE STUDY SHOWS GLIMPSE OF RED PLANET'S ANCESTRY From Purdue News March 18, 1997 WEST LAFAYETTE, Ind. -- While the controversy continues over whether a Martian meteorite bears evidence of ancient life on Mars, a Purdue University scientist says the rocky fragments can tell us something about the early life of the planet itself. Michael Lipschutz, professor of chemistry who has analyzed trace elements in 11 of the 12 known Martian meteorites, says the samples contain a different mix of volatile elements than do rock samples from Earth, indicating that the Red Planet was created from a different nebular womb. "It looks like the cloud of gas and dust from which Mars was born contained more volatile elements such as thallium, bismuth and cadmium than did the cloud from which Earth was formed," Lipschutz says. Prior studies of the oxygen isotopes in the Martian meteorites indicated that they all came from the same planet. But other studies, using nonvolatile chemical markers, had revealed differences in their composition, indicating that the samples had encountered different experiences as the planet formed and evolved. "Our study is the first to show that the characteristics revealed by the nonvolatile elements are also present in the volatile elements," Lipschutz says. "That is to say that these meteorites share some common characteristics, but due to differences in their composition, they belong to the three separate categories that are commonly used to distinguish these meteorites." He presented his findings today (3/18) at the 28th Lunar and Planetary Science Conference in Houston. Lipschutz, who has studied the solar system and meteorites for more than 30 years, based his findings on studies of 15 trace elements in 11 of the 12 meteorites identified as originating from the planet Mars. He will complete studies of the 12th meteorite this spring. His studies of the Martian meteorites focused on the volatile trace elements, the chemical elements that were most likely to condense last as the planet solidified from a cloud of dust and gas. Trace elements and ultratrace elements -- especially volatile ones found in parts per million or parts per billion -- can yield important information about a meteorite because the composition levels are so low that even the smallest change induced by a physical or chemical transformation is magnified into a relatively large change. In addition, the samples from Mars show that the planet has experienced at least two fractionation events -- events that separate the volatile trace elements from the non-volatile elements, Lipschutz says. "The amazing thing is that whatever chemical fractionation events Mars experienced, all of the elements -- volatile or not -- were able to remain and record the events," he says. "This is unlike the situation in other extraterrestrial bodies where late heating, caused for example by the shock of an impact, can vaporize the volatile elements and destroy evidence of past events. In the case of some of the meteorites from the moon, chemical elements were introduced by events such as volcanism, which also clouded the historical record." ----------------------------------------------------------------- CALTECH GEOLOGISTS FIND NEW EVIDENCE THAT MARTIAN METEORITE COULD HAVE HARBORED LIFE California Institute of Technology March 14, 1997 PASADENA -- Geologists studying Martian meteorite ALH84001 have found new support for the possibility that the rock could once have harbored life. Moreover, the conclusions of California Institute of Technology researchers Joseph L. Kirschvink and Altair T. Maine, and McGill University's Hojatollah Vali, also suggest that Mars had a substantial magnetic field early in its history. Finally, the new results suggest that any life on the rock existing when it was ejected from Mars could have survived the trip to Earth. In an article appearing in the March 13 issue of the journal Science, the researchers report that their findings have effectively resolved a controversy about the meteorite that has raged since evidence for Martian life was first presented in 1996. Even before this report, other scientists suggested that the carbonate globules containing the possible Martian fossils had formed at temperatures far too hot for life to survive. All objects found on the meteorite, then, would have to be inorganic. However, based on magnetic evidence, Kirschvink and his colleagues say that the rock has certainly not been hotter than 350 degrees Celsius in the past four billion years -- and probably has not been above the boiling point of water. At these low temperatures, bacterial organisms could conceivably survive. "Our research doesn't directly address the presence of life," says Kirschvink. "But if our results had gone the other way, the high-temperature scenario would have been supported." Kirschvink's team began their research on the meteorite by sawing a tiny sample in two and then determining the direction of the magnetic field held by each. This work required the use of an ultrasensitive superconducting magnetometer system, housed in a unique, nonmagnetic clean lab facility. The team's results showed that the sample in which the carbonate material was found had two magnetic directions -- one on each side of the fractures. The distinct magnetic directions are critical to the findings, because any weakly magnetized rock will reorient its magnetism to be aligned with the local field direction after it has been heated to high temperatures and cooled. If two such rock fragments are attached so that their magnetic directions are separate, but are then heated to a certain critical temperature, they will have a uniform direction. The igneous rock (called pyroxenite) that makes up the bulk of the meteorite contains small inclusions of magnetic iron sulfide minerals that will entirely realign their field directions at about 350 degrees C, and will partially align the field directions at much lower temperatures. Thus, the researchers have concluded that the rock has never been heated substantially since it last cooled some four billion years ago. "We should have been able to detect even a brief heating event over 100 degrees Celsius," Kirschvink says. "And we didn't." These results also imply that Mars must have had a magnetic field similar in strength to that of the present Earth when the rock last cooled. This is very important for the evolution of life, as the magnetic field will protect the early atmosphere of a planet from being sputtered away into space by the solar wind. Mars has since lost its strong magnetic field, and its atmosphere is nearly gone. The fracture surfaces on the meteorite formed after it cooled, during an impact event on Mars that crushed the interior portion. The carbonate globules that contain putative evidence for life formed later on these fracture surfaces, and thus were never exposed to high temperatures, even during their ejection from the Martian surface nearly 15 million years ago, presumably from another large asteroid or comet impact. A further conclusion one can reach from Kirschvink's work is that the inside of the meteorite never reached high temperatures when it entered Earth's atmosphere. This means, in effect, that any remaining life on the Martian meteorite could have survived the trip from Mars to Earth (which can take as little as a year, according to some dynamic studies), and could have ridden the meteorite down through the atmosphere by residing in the interior cracks of the rock and been deposited safely on Earth. "An implication of our study is that you could get life from Mars to Earth periodically," Kirschvink says. "In fact, every major impact could do it." Kirschvink's suggested history of the rock is as follows: The rock crystallized from an igneous melt some 4.5 billion years ago and spent about half a billion years on the primordial planet, being subjected to a series of impact-related metamorphic events, which included formation of the iron sulfide minerals. After final cooling in the ancient Martian magnetic field about four billion years ago, the rock would have had a single magnetic field direction. Following this, another impact crushed parts of the meteorite without heating it, and caused some of the grains in the interior to rotate relative to each other. This led to a separation of their magnetic directions and produced a set of fracture cracks. Aqueous fluids later percolated through these cracks, perhaps providing a substrate for the growth of Martian bacteria. The rock then sat more or less undisturbed until a huge asteroid or comet smacked into Mars 15 million years ago. The rock wandered in space until about 13,000 years ago, when it fell on the Antarctic ice sheet. ----------------------------------------------------------------- EUROPA: IS THERE LIFE UNDER ICE? Voice of America Transcript 14 March, 1997 Anncr: The voice of america presents -- New Horizons -- a weekly program on developments in science, technology and medicine. Today -- "Europa: Is There Life Under Ice?" -- a look at a frozen moon of Jupiter and the intriguing questions scientists are asking about it. BALLARD: "And then certainly what's really exciting for a lot of us is what's going to take place....when our community starts to mix and mingle with the nasa community in planning future exploration on the jovian moon of europa, which we believe has an ocean." Text: Robert Ballard, currently with the institute for exploration. Back in 1977, he and his colleagues took the mini-submarine Alvin down to the ocean floor off the Galapagos islands. And there they found a world that no human being had ever before seen -- strange life forms inhabiting an area near vents of hot water bubbling up from the sea floor; bacteria, clam-like creatures and red-plumed tube worms deriving nourishment from a hellish brew of hydrogen sulfide -- a substitute for sunlight in a sunless environment. Some scientists think it might just be possible that life on earth originated among sulfide deposits on the sea floor. Geologist Mark Hannington of the Geological Survey of Canada explains: Hannington: "As geologists we have a very good fossil record of these deposits forming right back to the very early beginning of time on earth when the oldest deposit that we know about is about three point five billion years old. The earth itself is only about four point six billion years old. And i guess from the origin of life point of view that these might have been very large oases for chemosynthetic life way back to two or three billion years ago." Text: So if this hypothesis is true, the earliest life forms would probably have resembled bacteria, living off of chemicals flushed from the center of the earth on plumes of superheated water bursting up through the ocean floor. Oceanographer Robert Ballard says this would change our entire view of life's origins: Ballard: "If you look at the early textbooks and our best guesses at the origin of life was this primordial soup in shallow water that a bolt of lightning hit, and all of a sudden we had amino acids and we had the beginning of the game, (that) may be just not the story at all -- and that it was really in a very stable, deep water setting in a primordial ocean where the game began. So there's lots that's going to happen in the next few years on this story." Text: So if life can exist undetected for millennia on earth's ocean floor, might the same be true on another body in our solar system -- one that may have an ocean? If a growing number of oceanographers and planetary scientists are right, then Europa -- one of the four close-in moons of Jupiter -- might be worth a closer look. Robert Ballard: Ballard: "....If you're going to find a highest possible candidate for finding life off this planet (earth), it appears to be Europa." Text: Why Europa? Why would this ice-covered moon of Jupiter -- so cold and forbidding in appearance -- be an incubator for life forms? The key word is volcanism -- not just the volcanoes that spew lava and ash onto terrified communities at the bases of mountains, but vents like those on earth's ocean floor that transfer geothermal heat to the ice-cold water two kilometers beneath the waves. At about the same time oceanographers were discovering tube worm communities on earth's ocean floor, nasa's voyager two space probe made the most amazing discovery near jupiter. Io, one of jupiter's close-in moons, had active volcanoes -- the first ever seen beyond earth. What's more, io is the lunar neighbor of europa. Might Europa have volcanic activity -- not out in the open where it can be seen by spacecraft cameras, but far beneath its icy surface, where hot volcanoes can create warm water, as we've seen on earth? University of Washington oceanographer John Delaney: Delaney: "For some reason that isn't always clear to scientists, those two rather powerful insights did not interact very much at first, although the first formal published interaction between the two concepts was a paper done by Steve Squyres... In 1983... In which (there was) the suggestion that Europa might have an ocean beneath the ice. And if it did after four point six billion years, then there had to be a significant heat source inside similar to what Io -- the most volcanically active body in the solar system -- has." Text: This concept was reinforced by spacecraft images -- both from the Voyager as well as more recent ones from the Galileo spacecraft. Not only is Europa's surface icy, but the pictures show there's something very strange about that ice. Astronomer Eugene Shoemaker of the lowell observatory explains: Shoemaker: "The funny thing about Europa is that there are hardly any craters there, in contrast with the next satellite out, Ganymede, and especially in contrast with Callisto. And what that fundamentally told us is that in terms of crater retention age, we were looking at one of the youngest surfaces in the solar system." Text: This past January, NASA released pictures of Europa taken by the Galileo probe that showed an icy surface with a jumble of ridges and bumps -- evidence, according to scientists, of melting and re-freezing. As Eugene Shoemaker sees it, something under the ice is generating heat: Shoemaker: "So we're seeing a surface that's been replaced piecemeal by internal activity within the satellite. Parts of that ice crust pull apart and new material wells up. Basically it's an ongoing process." Text: If there is heat-generating volcanism on Europa, what would cause it? The same thing, say astronomers, that creates the very visible volcanoes on Io -- the internal flexing caused by Jupiter's gravity as the tiny satellite orbits the huge planet. Planetary scientist Steven Squyres of Cornell University: Sqyres: "What happens is, because of its proximity to Jupiter, Europa itself is distorted into a somewhat elongated shape. It has a tide. The size of that tidal bulge is related to how close it is to Jupiter. If it's in a little closer, the bulge gets bigger. If it's out a little further, the bulge gets smaller. Because it's in this non-circular orbit, the bulge gets bigger and smaller and bigger and smaller each trip around the orbit. The satellite gets flexed back and forth. "Just as if you take a piece of wire or something and bend it back and forth rapidly, you will deposit heat in the object. The same thing happens to Europa. It gets flexed back and forth. And this is the process of tidal heating...... If it is sufficiently vigorous, it can lead to production of a liquid water ocean on Europa." Text: So while scientists are still not sure, the lines of evidence are pointing to a liquid ocean on Europa, covered by a layer of ice. Eugene Shoemaker believes that layer could vary in thickness: Shoemaker: "So there may be very thin parts in the ice and elsewhere it may be ten or maybe twenty kilometers thick -- overlying a very deep ocean 100 to 200 kilometers deep beneath that. So the bottom line is it looks as though --it isn't proven yet -- but it looks as though we're looking at another body with an ocean. It's the only other place in the solar system where we have an ocean of water. And if you want to look for life, that's where I'd put my chips." Text: But the question remains -- would volcanic heating and a warm water ocean automatically mean life on Europa? The University of Washington's John Delaney: Delaney: "That's a tough one. We have a population of one so far -- the earth -- in which we do find a close correlation between active volcanoes and the ability to sustain life, not just at the surface of the sea floor but actually down in the cracks in the floor. That's a fairly powerful new concept really. In the last five years perhaps we've gotten a lot more evidence that there is a close correlation between volcanism and the gases that are given off by volcanism. And microbial life forms that can actually make a living directly off the gas. "Then there are the microbial life forms that can make a living directly off the products of the bacteria and microbes that live off the gas. So you have all sorts of complexities that go with it." "I'm afraid at this point it's very difficult for us to... say: surely, there will be life. But i will tell you that it has opened the door to some really deep thinking on the part of a lot of us who have begun to ask the question: perhaps what planets do in one sense or another is create conditions under which life can start. And whether life gets as far as it has so that the organisms that live on a particular planet have press conferences or not is really the unusual aberration. But perhaps the beginning of simple forms of replicating organisms is not that far fetched." Text: As an example of the kinds of life that could evolve on the sea floor of Europa -- if, indeed, it has a liquid ocean -- Eugene Shoemaker points to what are perhaps the most ancient life forms on earth: Shoemaker: "There is a class of organism called Archaea, which are probably the predecessors of bacteria. They seem to be the most primitive. And the curious thing that has been discovered in the last ten years is that wherever there is a chemical source of energy, there is one of these critters -- a one celled organism -- that makes use of it. So that in itself makes one think that maybe the odds are pretty good that if there is enough heat on the floor of this ocean -- that's the big if -- if there is active volcanism or hot fluids coming out of the interior, providing chemicals that living organisms could take advantage of for metabolism -- that's what we're betting on. That's the kind of thing you might find." _______________________________________ End Marsbugs vol.4. n.6.