Life on Mars: latest issue of Marsbugs part one

Mark Pallen m.pallen at
Mon Aug 12 06:13:03 EST 1996


I enclose the latest issue of Marsbugs, which contains loads of links 
and info on the martian fossils.

Date: 8 Aug 1996 20:31:16 -0500
From: Julian Hiscox <julian_hiscox at>
Subject: Marsbugs- V.3. N.8. Part 1.
To: "Dr. Julian and Melissa Hiscox" <marsgene at>

                      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 at 
Julian Hiscox, Microbiology Department, BBRB 17, Room 361,  
University of Alabama at Birmingham, Birmingham, AL 35294-2170,  
USA, Julian_hiscox at 
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: 

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.
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 

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 at  WWW:
phone: day ++44(0)1715945254, eves ++44(0)1815057937, FAX 
Author, Microbial Underground:
"Presume not mice to scan, the proper study of mankind is man"
(not) Alexander Pope

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