Possible Life on Mars

Mon, 12 Aug 1996 20:08:20 -0400

Subject: Life on Mars: latest issue of Marsbugs part one
From: m.pallen@ic.ac.uk (Mark Pallen)
Date: 12 Aug 1996 04:13:03 -0700

This message is an issue of "Marsbugs". It contains links on the possible
martian fossils. See the future issue: _Science_ September 16, 1996.

Date: 8 Aug 1996 20:31:16 -0500
From: Julian Hiscox <julian_hiscox@micro.microbio.uab.edu>
Subject: Marsbugs- V.3. N.8. Part 1.
To: "Dr. Julian and Melissa Hiscox" <marsgene@aol.com>

Subject: Time:
8:29 PM
OFFICE MEMO Marsbugs: V.3. N.8. Part 1. Date:

MARSBUGS: The Electronic Exobiology Newsletter
Volume 3, Number 8, 8 August, 1996.


David Thomas, Department of Biological Sciences, University of
Idaho, Moscow, ID, 83844-3051, USA, thoma457@uidaho.edu.

Julian Hiscox, Microbiology Department, BBRB 17, Room 361,
University of Alabama at Birmingham, Birmingham, AL 35294-2170,
USA, Julian_hiscox@micro.microbio.uab.edu.

MARSBUGS is published on a weekly to quarterly basis as warranted
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The purpose of this newsletter is to provide a channel of
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them. We, the editors, envision MARSBUGS as a medium in which
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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.


1) Editors' note.

American Association for the Advancement of Science

NASA release 96-160


NASA release I96-6



The past few days have presented us with some very exciting
information. Several agencies have released information
concerning the possible martian microfossils. We have tried to
provide you, the readers, with all of this information, even
though much of it is repetition. We highly suggest reading the
upcoming issue of Science in order to get the story straight from
the researchers involved. The full text of the article can be found


(Featured in 16 August 1996 Science)
American Association for the Advancement of Science News Release

Ever since scientists learned that water once flowed on Mars,
they've wondered whether life might also have flourished on the
apparently now-dead planet. In the 16 August issue of Science,
McKay et al report the first identification of organic compounds
in a Martian meteorite. The authors further suggest that these
compounds, in conjunction with a number of other mineralogical
features observed in the rock, may be evidence of ancient Martian
microorganisms. The paper's authors are David S. McKay and
Everett K. Gibson, Jr., of NASA's Johnson Space Center in
Houston, TX; Kathie L. Thomas-Keprta of Lockheed Martin in
Houston, TX; Hojatollah Vali of McGill University in Montreal,
Quebec; Christopher S. Romanek of the University of Georgia's
Savannah River Ecology Laboratory in Aiken, SC; and Simon J.
Clemett, Xavier D. F. Chllier, Claude R. Maechlin, and Richard N.
Zare of Stanford University in Stanford, CA.

Organic (complex, carbon-based) molecules are the requisite
building blocks of life on Earth. The authors looked for signs
of such molecules and other mineralogical and textural
indications of past life within the pore space and fractures of
meteorite Allan Hills 84001 (ALH84001), one of only 12 meteorites
identified as having come from Mars. ALH84001 is the oldest of
the Martian dozen, having crystallized from molten rock about 4.5
billion years ago, early in the planet's evolution, and it is the
only Martian meteorite to contain significant carbonate minerals.
(The carbonates formed sometime after the rock, perhaps about 3.6
billion years ago.)

About 15 million years ago, a major asteroid impact on Mars threw
ALH84001 into space, where it eventually fell onto an ice field
in Antarctica about 13,000 years ago. ALH84001, which shows
little evidence of terrestrial weathering, was discovered by
meteorite-hunting scientists in 1984 and only recently identified
at Martian. ALH84001 is riven with tiny fractures resulting
primarily from impacts that occurred while the rock was on Mars.
The secondary carbonates formed along with some of these
fractures. The Science authors prepared thin sample sections
that included these pre-existing fractures, and found on their
surfaces a clear and distinct distribution of polycyclic aromatic
hydrocarbons (PAHs), organic molecules containing multiple
connected rings of carbon atoms--the first organic molecules ever
seen in a Martian rock. A variety of contamination checks and
control experiments indicated that the organic material was
indigenous to the rock and was not the result of terrestrial
contamination. For example, the authors noted that the
concentration of PAHs increases inward, whereas terrestrial
contamination likely would have resulted in more PAHs on the
exterior of the rock.

The big question is: where did the PAHs come from? It is
thought that PAHs can form one of two ways: non-biologically,
during early star formation; or biologically, through the
activity of bacteria or other living organisms, or their
degradation (fossilization). On Earth, PAHs are abundant as
fossil molecules in ancient sedimentary rocks, coal and
petroleum, the result of chemical changes that occurred to the
remains of dead marine plankton and early plant life. They also
occur during partial combustion, such as when a candle burns or
food is grilled.

To address the origin of these PAHs, the authors examined the
chemistry, mineralogy, and texture of carbonates associated with
PAHs in the Martian meteorite. Under the transmission electron
microscope, the carbonate globules were seen to contain fine-
grained magnetite and iron-sulfide particles. From these and
other analyses, the authors developed a list of observations
about the carbonates and PAHs that, taken individually, could be
explained by non-biological means. However, as they write in
their Science article, "when considered collectively ... we
conclude that [these phenomena] are evidence for primitive life
on early Mars." Some of their observations are as follows:

* The higher concentrations of PAHs were found associated with
the carbonates.

* The carbonates formed within the rock fissures, about 3.6
billion years ago, and are younger than the rock itself.

* The magnetite and iron-sulfide particles inside the carbonate
globules are chemically, structurally and morphologically similar
to magnetosome particles produced by bacteria on Earth.

* High-resolution scanning electron microscopy revealed on the
surface of the carbonates small (100 nanometers) ovoids and
elongated features. Similar textures have been found on the
surface of calcite concretions grown from Pleistocene groundwater
in southern Italy, which have been interpreted as representing

* Some earlier reports had suggested that the temperature at
which the ALH84001 carbonates formed was as high as 700 degrees
C--much too hot for any kind of life. However, the isotopic
composition of the carbonates, and the new data on the magnetite
and iron-sulfide particles, imply a temperature range of 0 to 80
degrees C, cool enough for life.

* The magnetite--a mineral that contains some ferric (Fe3+) iron,
perhaps indicating formation by oxidation (the addition of
oxygen)--and iron sulfide--a mineral that can be formed by
reduction (the loss of oxygen)--were found in close proximity in
the Martian meteorite. On Earth, closely associated
mineralogical features involving both oxidation and reduction are
characteristic of biological activity.

Science is the official journal of the American Association for
the Advancement of Science (AAAS) in Washington, DC, the world's
largest general science organization.

NASA release 96-160

A NASA research team of scientists at the Johnson Space Center
(JSC), Houston, TX, and at Stanford University, Palo Alto, CA,
has found evidence that strongly suggests primitive life may have
existed on Mars more than 3.6 billion years ago. The NASA-funded
team found the first organic molecules thought to be of Martian
origin; several mineral features characteristic of biological
activity; and possible microscopic fossils of primitive,
bacteria-like organisms inside of an ancient Martian rock that
fell to Earth as a meteorite. This array of indirect evidence of
past life will be reported in the August 16 issue of the journal
Science, presenting the investigation to the scientific community
at large for further study. The two-year investigation was co-
led by JSC planetary scientists Dr. David McKay, Dr. Everett
Gibson and Kathie Thomas-Keprta of Lockheed-Martin, with the
major collaboration of a Stanford team headed by Professor of
Chemistry Dr. Richard Zare, as well as six other NASA and
university research partners.

"There is not any one finding that leads us to believe that this
is evidence of past life on Mars. Rather, it is a combination of
many things that we have found," McKay said. "They include
Stanford's detection of an apparently unique pattern of organic
molecules, carbon compounds that are the basis of life. We also
found several unusual mineral phases that are known products of
primitive microscopic organisms on Earth. Structures that could
be microscopic fossils seem to support all of this. The
relationship of all of these things in terms of location--within
a few hundred thousandths of an inch of one another--is the most
compelling evidence."

"It is very difficult to prove life existed 3.6 billion years ago
on Earth, let alone on Mars," Zare said. "The existing standard
of proof, which we think we have met, includes having an
accurately dated sample that contains native microfossils,
mineralogical features characteristic of life, and evidence of
complex organic chemistry."

"For two years, we have applied state-of-the-art technology to
perform these analyses, and we believe we have found quite
reasonable evidence of past life on Mars," Gibson added. "We
don't claim that we have conclusively proven it. We are putting
this evidence out to the scientific community for other
investigators to verify, enhance, attack--disprove if they can --
as part of the scientific process. Then, within a year or two,
we hope to resolve the question one way or the other."

"What we have found to be the most reasonable interpretation is
of such radical nature that it will only be accepted or rejected
after other groups either confirm our findings or overturn them,"
McKay added.

The igneous rock in the 4.2-pound, potato-sized meteorite has
been age-dated to about 4.5 billion years, the period when the
planet Mars formed. The rock is believed to have originated
underneath the Martian surface and to have been extensively
fractured by impacts as meteorites bombarded the planets in the
early inner solar system. Between 3.6 billion and 4 billion
years ago, a time when it is generally thought that the planet
was warmer and wetter, water is believed to have penetrated
fractures in the subsurface rock, possibly forming an underground
water system.

Since the water was saturated with carbon dioxide from the
Martian atmosphere, carbonate minerals were deposited in the
fractures. The team's findings indicate living organisms also
may have assisted in the formation of the carbonate, and some
remains of the microscopic organisms may have become fossilized,
in a fashion similar to the formation of fossils in limestone on
Earth. Then, 16 million years ago, a huge comet or asteroid
struck Mars, ejecting a piece of the rock from its subsurface
location with enough force to escape the planet. For millions of
years, the chunk of rock floated through space. It encountered
Earth's atmosphere 13,000 years ago and fell in Antarctica as a

It is in the tiny globs of carbonate that the researchers found a
number of features that can be interpreted as suggesting past
life. Stanford researchers found easily detectable amounts of
organic molecules called polycyclic aromatic hydrocarbons (PAHs)
concentrated in the vicinity of the carbonate. Researchers at
JSC found mineral compounds commonly associated with microscopic
organisms and the possible microscopic fossil structures.

The largest of the possible fossils are less than 1/100 the
diameter of a human hair, and most are about 1/1000 the diameter
of a human hair--small enough that it would take about a thousand
laid end-to-end to span the dot at the end of this sentence.
Some are egg-shaped while others are tubular. In appearance and
size, the structures are strikingly similar to microscopic
fossils of the tiniest bacteria found on Earth.

The meteorite, called ALH84001, was found in 1984 in Allan Hills
ice field, Antarctica, by an annual expedition of the National
Science Foundation's Antarctic Meteorite Program. It was
preserved for study in JSC's Meteorite Processing Laboratory and
its possible Martian origin was not recognized until 1993. It is
one of only 12 meteorites identified so far that match the unique
Martian chemistry measured by the Viking spacecraft that landed
on Mars in 1976. ALH84001 is by far the oldest of the 12 Martian
meteorites, more than three times as old as any other.

Many of the team's findings were made possible only because of
very recent technological advances in high- resolution scanning
electron microscopy and laser mass spectrometry. Only a few
years ago, many of the features that they report were
undetectable. Although past studies of this meteorite and others
of Martian origin failed to detect evidence of past life, they
were generally performed using lower levels of magnification,
without the benefit of the technology used in this research. The
recent discovery of extremely small bacteria on Earth, called
nanobacteria, prompted the team to perform this work at a much
finer scale than past efforts.

The nine authors of the Science report include McKay, Gibson and
Thomas-Keprta of JSC; Christopher Romanek, formerly a National
Research Council post-doctoral fellow at JSC who is now a staff
scientist at the Savannah River Ecology Laboratory at the
University of Georgia; Hojatollah Vali, a National Research
Council post-doctoral fellow at JSC and a staff scientist at
McGill University, Montreal, Quebec, Canada; and Zare, graduate
students Simon J. Clemett and Claude R. Maechling and post-
doctoral student Xavier Chillier of the Stanford University
Department of Chemistry.

The team of researchers includes a wide variety of expertise,
including microbiology, mineralogy, analytical techniques,
geochemistry and organic chemistry, and the analysis crossed all
of these disciplines. Further details on the findings presented
in the Science article include:

* Researchers at Stanford University used a dual laser mass
spectrometer--the most sensitive instrument of its type in the
world--to look for the presence of the common family of organic
molecules called PAHs. When microorganisms die, the complex
organic molecules that they contain frequently degrade into PAHs.
PAHs are often associated with ancient sedimentary rocks, coals
and petroleum on Earth and can be common air pollutants. Not
only did the scientists find PAHs in easily detectable amounts in
ALH84001, but they found that these molecules were concentrated
in the vicinity of the carbonate globules. This finding appears
consistent with the proposition that they are a result of the
fossilization process. In addition, the unique composition of
the meteorite's PAHs is consistent with what the scientists
expect from the fossilization of very primitive microorganisms.
On Earth, PAHs virtually always occur in thousands of forms, but,
in the meteorite, they are dominated by only about a half-dozen
different compounds. The simplicity of this mixture, combined
with the lack of light-weight PAHs like naphthalene, also differs
substantially from that of PAHs previously measured in non-
Martian meteorites.

* The team found unusual compounds--iron sulfides and magnetite--
that can be produced by anaerobic bacteria and other microscopic
organisms on Earth. The compounds were found in locations
directly associated with the fossil-like structures and carbonate
globules in the meteorite. Extreme conditions--conditions very
unlikely to have been encountered by the meteorite--would have
been required to produce these compounds in close proximity to
one another if life were not involved. The carbonate also
contained tiny grains of magnetite that are almost identical to
magnetic fossil remnants often left by certain bacteria found on
Earth. Other minerals commonly associated with biological
activity on Earth were found in the carbonate as well.

* The formation of the carbonate or fossils by living organisms
while the meteorite was in the Antarctic was deemed unlikely for
several reasons. The carbonate was age dated using a parent-
daughter isotope method and found to be 3.6 billion years old,
and the organic molecules were first detected well within the
ancient carbonate. In addition, the team analyzed representative
samples of other meteorites from Antarctica and found no evidence
of fossil-like structures, organic molecules or possible
biologically produced compounds and minerals similar to those in
the ALH84001 meteorite. The composition and location of PAHs
organic molecules found in the meteorite also appeared to confirm
that the possible evidence of life was extraterrestrial. No PAHs
were found in the meteorite's exterior crust, but the
concentration of PAHs increased in the meteorite's interior to
levels higher than ever found in Antarctica. Higher
concentrations of PAHs would have likely been found on the
exterior of the meteorite, decreasing toward the interior, if the
organic molecules are the result of contamination of the
meteorite on Earth.

Additional information may be obtained at 1 p.m. EDT via the
Internet at http://www.jsc.nasa.gov/pao/flash/

Dr Mark Pallen, Senior Lecturer in Medical Microbiology,
St Bartholomew's Hospital Medical College, London, EC1A 7BE
currently on a Research Leave Fellowship at Imperial College 
Rm 502, Dept of Biochem, Imperial College, London, SW7 2AY
email:m.pallen@ic.ac.uk  WWW: 
phone: day ++44(0)1715945254, eves ++44(0)1815057937, FAX 
Author, Microbial Underground: http://www.qmw.ac.uk/~rhbm001
"Presume not mice to scan, the proper study of mankind is man"
(not) Alexander Pope