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.

