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(meteorobs) life in martian meteorite: ins and outs...
(this is an article taken from the website of the Dutch Meteor Society
(DMS), http://www.pidot net/~terkuile/meteors/dms.htm)
ANCIENT LIFE ON MARS?!?
Scientists explore a Close Encounter of a Meteoritic Kind
By Marco Langbroek, August 15 1996
Introduction: Is there something Out There...?!?
Mars has fascinated mankind for ages. For some reason, Mars was thought to be a
reasonable place for living creatures to dwell ever since the Dutch pioneer
observer
Christiaan Huygens saw the first marks on its surface in the evening of
November 28,
1659. Such was the conviction about life on Mars, that most people were not
surprised
when US resident and Mars afficionado Percival Lowell pushed the idea of
intelligent
beings having created the famous illusionary 'canals' seen on its surface by
Earthling
observers in the late ninetheenth century, though the more sceptic of his
contemporary
scientists repudiated the idea of canals -but not necessarily of life on
Mars. And even
after Lowell and his canals seemed to have entered the realm of oldfashioned
lore, the
idea of life on Mars did not left the minds of scientists, and certainly not
that of the
public.
In 1976, life on Mars was a hot topic again, when two NASA Viking spacecraft
landers
probed its surface in search for evidence of life. Ambiguous results of
different experi-
ments resulted in quite some discussions, but in the end the NASA team
concluded that
there was no definite evidence of life -at least on the few square meters of
Mars that were
investigated by the Viking landers. Still, the idea did not die. Talk was
going on that life
might once have existed when Mars experienced better times and was not the
chilly scene
of dry cold desserts, violent duststorms and frozen water and Carbondioxide
locked in
seasonally expanding and retreating polar caps that it is today. Talk
continued, fueled by
research on SNC-meteorites that are believed to be pieces of Mars ejected
from it's
surface by asteroid impacts, that fluid water and a more 'earthly'
atmosphere composition
might have been present on Mars in a not too distant past and that
watercontaining layers
might be locked somewhere beneath the surface of Mars, providing a shielded
environ-
ment against the harmfull UltraViolet radiation and a possible exile for
primitive
lifeforms.
Prelude to first contact: 'Is everything ready at the dark side of the Moon...?'
So much for the past. While Earthlings spend decades peering at Mars through
telescopes,
probing the planet by radar and sending spacecraft in trying to solve the
everlasting
enigma of the red planet, the answer to all speculations seems to have been
quite nearby
for 13000 years, in a remote corner of our own planet called Antarctica.
13000 years
ago, around the time of the Būlling interstadial that marked the first signs
of the end of
the Weichselian glacial (called the Wisconsin in the USA), when Magdalenian
people
hunted reindeer in Europe's tundra and gallery forest landscape after the
retreatment of
the glaciers and the first proto-Americans entered this continent through
the Beringian
landbridge (or paddled along it's shore by canoo), a short flash of light
illuminated the
desolate Antarctic skies for a few seconds. A piece of fusion crust covered
rock of
Martian origin, 1.9 kg weight after its short but violent travel through the
Earth's
atmosphere, slammed into the ice, unseen by any human eye. There it lay for
13 millenia,
steadily accumulating a cover of snow and ice and then slowly losing that
again as the ice
was pushed up against the nearby hills and slowly eroded away. Finally, in
the early
southern summer of 1984, a member of the US Antarctic Search for Meteorites pro-
gramm picked it up from the blue ice fields near the Allan Hills, some 300
km distant
from the US McMurdo Station. It was the first meteorite recovered that field
season. And
yet, it's special properties were not recognized. Mislabeled (!) as a
Diogenite, a rare kind
of achondritic meteorites not related to Mars but (presumably) to asteroidal
mantles, it
disappeared into the depots of the Antarctic search programm in Houston for
a while,
designated as meteorite ALH84001, now and then being taken out and sectioned
for an
examination by a scientist.
ALH84001: A Close Encounter of a Meteoritic Kind
It was not untill ten years later (!) that the true character of the rock
was recognized.
During an investigation into Diogenite meteorites in the early ninethies,
scientist David
Mittlefehldt of Lockheed Engineering and Sciences Co. obtained a thin
section of ALH
84001 and noted that its peculiar composition did not fitt in well among the
Diogenites,
but seemed to be affiliated to that of the SNC-class of meteorites, rare
basaltic meteorites
that already where tought to originate from Mars because of their basaltic
texture and
their noble gas composition similar to that established for the Martian
environment by the
Viking landers. After he announced the unmasking of ALH84001 as a Martian
meteorite
in the journal Meteoritics in March 1994, along with a study into the
meteorite's
mineralogy, petrography and geochemistry, the meteorite became a focus of
scientific
interrest because of its comparatively extreme age for a meteorite from the
SNC-clan and
in many respects very unusual composition. Much attention got the Carbonate
globules
embedded into it's basaltic orthopyroxene texture, and it are these
Carbonate globules that
are containing the material that is now causing so much excitement. In a
press conference
hastily gathered on August 7 1996 after news had leaked to the press too
early, NASA
announced to an excited audience that her scientists had found traces of
organics and
structures in the globules that might have a biologic origin: 3.465 billion
years ago,
primitive life indeed seemed to have existed on Mars!
The evidence: Extra-Terrestrial organics and suggestive microfossil-like
structures
Now, what exactly have the NASA scientists found? Fossilized little green
men? Martian
fungi or lichens? Certainly not. Not even little green bacteria. Actually,
they have found
nothing realy conclusive so far: some organics, which are not really
remarkable in itself,
and something what looks like fossilized bacteria. Yet, all together this
opens possibilities
which are far stretching. Though each line of evidence can be discounted for
individually,
together they form a strong argument for the opinion that life once might
have existed on
Mars. US President Bill Clinton, though confusing meteors and meteorites in
his speech,
was right when he announced to the gathered press in front of the White
House: 'It
speaks of the possibility of life. If this discovery is confirmed, it will
surely be one of the
most stunning insights into our universe that science has ever uncovered...'.
There are several lines of evidence that are put forward by the NASA
scientists. Let's
examine a few, as well as the arguments that can be put forward against
them. First,
they've found (by means of the technique called 'mass spectrometry') that
the meteorite
contains Polycyclic Aromatic Hydrocarbons (PAH's), in other words: organic
molecules.
Organic molecules of non-biological origin have been found in many
meteorites, but
according to the scientists the PAH's in ALH84001 are 'more simple than in other
meteorites' and more compatible with a biologic origin. They don't believe
they stem
from contamination that occured after the meteorite fel to Earth: the PAH's
are deep
inside the meteorite, but not present near the outside which is an argument
against leaking
in of Earth contaminants from the Antarctic ice and the Earth atmosphere.
However,
neither of the scientists involved is an expert in this tricky matter of
micro-sediments.
The Calcium Carbonate globules in ALH84001 (which are certainly
extra-terrestrial and
dated at 3.6 billion years, younger than the host rock itself which has a
dating of 4.5
billion years), feature rims that contain 40 to 50 nm large cristals of the
minerals
magnetite (an iron-oxide), phyrotite and gregite. All these can have an
anorganic origin,
but all of them are also produced by Earthly micro-organisms. The shapes of
the crystals
of magnetite and gregite are quite similar to the shapes of crystals of
these minerals
produced by micro-organisms in a low temperature fluid environment on Earth.
Oppo-
nents however point to the seeming contradiction introduced by research by
several
scientists that suggest that the Calcium Carbonates in ALH84001 containing
the mineral
crystals formed at rather high temperatures, near 700 C.
The most exiting -and controversial- things found by the scientists are the
tiny little
structures inside the meteorite, only 100 to 200 nm large, that resemble
fossilized bacteria
in shape. Yet, they have not been investigated for organic contents,
composition and have
not been investigated for evidence of a cellular structure. In addition,
they are very small
compared to Earthly fossilized bacteria, like those found in Australian
chert with an age
slightly younger than the Carbonate globules in ALH84001. And again, if the
Calcium
Carbonates in ALH84001 indeed formed at temperatures of 700 C or higher,
this is not
the most likely environment to expect micro-organisms -at least on Earth it
is not.
Yet, all these lines of evidence are intruiging and combined they form an
impressive case
and certainly warrant further investigation into the matter. If all the
things found do not
originate in extra-terrestrial life, they at least come very close, and the
scientists in
question need certainly not to be ashamed if it turns out that they have
been tricked by
coincidence. But if it all does turn out to be extra-terrestrial life
indeed, this is a true
turning point in history: the first time that life has been found that
originated outside
Earth, even though it are 'only' primitive micro-organisms and not
Extra-Terrestrial
intelligence ready to 'phone home'. It is an answer to a question that has
wondered many
generations of mankind: is there something else out there that lives...? If
the spectacular
discoveries presented by the NASA scientists can be further investigated and
confirmed,
the answer might be a definite yes: if life once flourished on early Mars
too, life might be
Universal indeed. And what about the posibilities that it still exists,
somewhere deep
down the Martian crust? Shielded against the harmfull ultraviolet, there's
nothing against
that possibility.
The warnings from the past
Still, one has to be carefull for too rapid a conclusion, and for this
reason a lot of
scientists in the field of cosmochemistry and microbiology seem to hold an
attitude of
'sceptic optimism' towards the recent findings. For people that know the
history of their
field, the claim of 'fossil life in meteorites' is all too familiar. In
1961, Bartholomew
Nagy and his coworkers launched two papers on the alledged biologic contents of
carbonaceous chondrites, a very primitive kind of chondritic meteorites
containing Carbon
that are now believed to date from the very early origins of our solar
system. In the first
paper, they wrote that the Hydrocarbons in the Orgueil carbonaceous
meteorite 'resemble
in many important aspects the hydrocarbons in the products of living things
and sediments
on earth'. In a later paper, they presented microscopic structures
resembling fossilized
primitive life forms. Debates about the matter ran for over a decade, and
then gradually
died. Most critics, and eventually also Nagy, came to agree that the
structures resembling
primitive organisms were either contaminants from Earth or particular forms
of minerals
that tricked the investigators. As for the hydrocarbons in these meteorites,
scholars now
agree that they are of non-biologic origin. Yet, they can have provided the
building
blocks for life to emerge on Earth, and maybe on Mars. Coupled to the recent
findings
concerning ALH84001 and the early history of Mars, the idea of meteorites
providing
cheap space travel from planet to planet of living organisms or their basic
compounds, a
thought nicknamed 'panspermia', got a definite boost. Who knows: our origins
might
indeed be located elsewhere in this Universe, and the alledged Martian
microbes and their
Earthly cousins could well be very closely related to each other.
From the past to the future: this is Earth calling...
For sure, when you take a look at Mars through your telescope, it will
undoubtedly be
another planet to us Earthlings than it was before: somewhere out there,
life may have
existed in a distant past, and might still exist in the dark depths of
Utopia, Trivium
Charontis, Tharsis and all those other places so familiar to Earthling Mars
observers.
If the discoveries can be confirmed, and if future space explorations
suggest that primitive
life still may exist down there in the depths of the red planet, this
exposes some ethic
problems: what to do with those Martians and their environment? If there's
still life on
Mars, though primitive, shouldn't we leave their habitat alone? Though space
probes are
sterilized, the procedure can never been waterthight, as is proven in the
past. Earthling
contamination can endanger the Martian environment. We could unwantingly
exterminate
our single-celled cosmic neighbours, just by our curiousity. As Carl Sagan
wrote in 1980
in his best-selling book 'Cosmos': 'Mars is for the Martians, even if it are
only micro-
bes'. I think he is right.
Future might have more for us in store. SETI, the Search For Extra
Terrestrial Intelligen-
ce, has now become a much more significant endeavour even in the view of
it's largest
critics. And even before the recent findings, NASA had planned to launch an
investigati-
on programm concerning Mars including space probes, Mars vehicles and sample
return
missions. With the recent findings, these plans certainly will get more
support and more
attention from scientists, the public and hopefully politicians too.
President Clinton's
addressing of the topic short before the NASA press conference took place
certainly
sounded hopefull. So, even if it turns out that ALH84001 did not bring life
to Earth, it
certainly brought life into the US space exploration of that mysterious red
planet we call
Mars.
Sources:
-NASA press conference, August 7 1996
-Time Magazine, August 19 1996, p.42-49.
-Burke J.G., 1986: Cosmic Debris, meteorites in history, p.312-316.
-Drake M.J. et al., 1994: Meteoritics 29, p.854-859.
-Firsoff V.A., 1969: The World of Mars.
-Jull A.J.T. et al., 1995: Meteoritics 30, p.311-318.
-Lutgens F.K. and Tarbuck E.J., 1989: Essentials of Geology.
-Mittlefehldt D.W., 1994: Meteoritics 29, p.214-221.
-McSween H.Y., 1994: Meteoritics 29, p.757-779.
-Pannekoek A.J. and Van Straaten L.M.J.U. (eds.), 1984: Algemene Geologie.
-Sagan C., 1980: Cosmos (Chapter 5: Blues for a Red Planet).
-Wanders A.J.M., 1956: Het raadsel Mars.
-Wanders A.J.M., 1979: Het Marsavontuur, van Fiction (?) tot Science.
-Warren P.H., 1994: Meteoritics 29, p.152-153.
-Warren P.H. and Kallemeyn G.W., 1996: Meteoritics & Planetary Science 31,
p.97-105.
-Wenthworth S.J. and Gooding J.L., 1994: Meteoritics 29, p.860-863.
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