Life on Mars?
Dave Smith
bacterial life exists on Mars.
It showed that microscopic worm-like structures found in a Martian
meteorite that hit the Earth 13,000 years ago are almost certainly
fossilised bacteria. The so-called bio-morphs are embedded beneath the
surface layers of the rock, suggesting that they were already present
when the meteorite arrived, rather than being the result of subsequent
contamination by Earthly bacteria.
“This is very strong evidence of life on Mars,” said David Mackay, a
senior scientist at the Nasa Johnson Space Centre , who was part of
the team of scientists that originally investigated the meteorite when
it was discovered in 1984.
In a 1996 study of the sample, Dr Mackay and others argued that the
microfossils were evidence of life, but sceptics dismissed the claims,
saying that similar-shaped structures might not be biological. The new
analyses, the product of high resolution electron microscopy, make a
strong case for the Allan Hills 84001 Meteorite having carried Martian
life to Earth. The microscopes were focused on tiny magnetite crystals
present in the surface layers of the meteorite, which have the form of
simple bacteria. Some argued that these could be the result of a
carbonate breaking down in the heat of the impact.
The new analyses show that this is very unlikely to have resulted in
the kinds of structures seen in the rock. Close examination suggested
that about 25 per cent of the crystal structures were chemically
consistent with being formed from bacteria.
“We feel vindicated. We’ve shown the alternate explanation is
absolutely incorrect, leading us back to our original position that
these structures are formed by bacteria on Mars,” Dr Mackay said.
Dennis Bazylinski, an astrobiologist from the University of Nevada who
peer-reviewed the findings, said: “Until now I was on the fence but
this paper has really thrown out the non-biological explanation.”
However, he added that the study was not “smoking gun” for life on
Mars. “One meteorite is never going to answer such a complex
question,” he said.
According to scientists, the meteorite was broken off the surface of
Mars by the impact of an asteroid, and reached Earth after floating
through space for about 16 million years. It landed in Allan Hills in
Antarctica. Scientists were able to trace the meteorite back to Mars,
as its chemical composition matched the relative proportions of
various gases measured in observations of the atmosphere of Mars made
by the Viking spacecraft in the 1970s.
The meteorite also preserves evidence of liquid water on Mars,
suggesting that the planet may have had more suitable conditions for
life to develop in the past. The investigation was published in the
November issue of Geochimica et Cosmochimica Acta, the journal of the
Geochemical and Meteoritic Society. Nasa is expected to announce the
findings formally on Monday.
The team has also been studying two other Martian meteorites — Nakhla,
which landed in Egypt in 1911, and Yamato 593, which was found by a
Japanese expedition to Antarctica. In research due to be published
shortly, the scientists claim that both of these fossils also show
evidence of microbial life.
Bill Clinton, then the US President, said of the research in 1997: “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. Its implications are as far-reaching
and awe-inspiring as can be imagined.”
http://www.timesonline.co.uk/tol/news/science/space/article6934078.ece
According to scientists, the meteorite was broken off the surface of
Mars by the impact of an asteroid, and reached Earth after floating
through space for about 16 million years. It landed in Allan Hills in
Antarctica. Scientists were able to trace the meteorite back to Mars,
as its chemical composition matched the relative proportions of
various gases measured in observations of the atmosphere of Mars made
by the Viking spacecraft in the 1970s.
The meteorite also preserves evidence of liquid water on Mars,
suggesting that the planet may have had more suitable conditions for
life to develop in the past. The investigation was published in the
November issue of Geochimica et Cosmochimica Acta, the journal of the
Geochemical and Meteoritic Society. Nasa is expected to announce the
findings formally on Monday.
The team has also been studying two other Martian meteorites — Nakhla,
which landed in Egypt in 1911, and Yamato 593, which was found by a
Japanese expedition to Antarctica. In research due to be published
shortly, the scientists claim that both of these fossils also show
evidence of microbial life.
Bill Clinton, then the US President, said of the research in 1997: “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. Its implications are as far-reaching
and awe-inspiring as can be imagined.”
Lance
> Nasa scientists have produced the most compelling evidence yet that
> bacterial life exists on Mars.
>
Interesting!
Lance
Mark....@bristol.ac.uk
: Nasa scientists have produced the most compelling evidence yet that
: bacterial life exists on Mars.
Superb! I'm still not 100% though, I need to see more examples to overcome
natural skepticism. And also an explanation of how these
"bacteria" evolved so simmilarly to those on Earth.
Mark
--
PG
KtvHpn.E...@bath.ac.uk...
I would like to see something other than the Times article, from an official
source, on this. Curiously I can find no other mentions of this latest
reinterpretation of the data anywhere other than in the Times and other
mainly European media and blog outlets, next to nothing from the US, and
nothing whatsover from NASA themselves.
pg
PG
4b127dc4$0$906$ba4a...@news.orange.fr...
Ok after a lot of searching (and Google didn't help for once) I found this
on the Dawkins forum:
"The investigation was published in the November issue of Geochimica et
Cosmochimica Acta, the journal of the Geochemical and Meteoritic Society.
Nasa is expected to announce the findings formally on Monday".
pg
PG
And here is the abstract from the aforementioned website (the full article
pdf has to be purchased):
"The Martian meteorite ALH84001 preserves evidence of interaction with
aqueous fluids while on Mars in the form of microscopic carbonate disks.
These carbonate disks are believed to have precipitated 3.9 Ga ago at
beginning of the Noachian epoch on Mars during which both the oldest extant
Martian surfaces were formed, and perhaps the earliest global oceans.
Intimately associated within and throughout these carbonate disks are
nanocrystal magnetites (Fe3O4) with unusual chemical and physical
properties, whose origins have become the source of considerable debate. One
group of hypotheses argues that these magnetites are the product of partial
thermal decomposition of the host carbonate. Alternatively, the origins of
magnetite and carbonate may be unrelated; that is, from the perspective of
the carbonate the magnetite is allochthonous. For example, the magnetites
might have already been present in the aqueous fluids from which the
carbonates were believed to have been deposited. We have sought to resolve
between these hypotheses through the detailed characterization of the
compositional and structural relationships of the carbonate disks and
associated magnetites with the orthopyroxene matrix in which they are
embedded. Extensive use of focused ion beam milling techniques has been
utilized for sample preparation. We then compared our observations with
those from experimental thermal decomposition studies of sideritic
carbonates under a range of plausible geological heating scenarios. We
conclude that the vast majority of the nanocrystal magnetites present in the
carbonate disks could not have formed by any of the currently proposed
thermal decomposition scenarios. Instead, we find there is considerable
evidence in support of an alternative allochthonous origin for the magnetite
unrelated to any shock or thermal processing of the carbonates."
So not quite so hyped up as the Times Online piece, but interesting.
Mark....@bristol.ac.uk
: So not quite so hyped up as the Times Online piece, but interesting.
Thanks for posting that - interesting. While we are probably all secretly
hoping that the discovery of extraterrestrial life will be a blinding
revelation that convinces most of science at once, the most likely
scenario is probably a slow accumulation of evidence that slowly converts
the mainstream bit by bit. These discoveries at least should provide the
impetus for a serious exploration of Mars to get more evidence.
Mark
--
PG
I've seen no sign of the promised official update from NASA. Anyone else
come across it? Perhaps it was another piece of creative writing from the
Times, based on the rather less than exciting Geochimica et Cosmochimica
Acta article of several weeks previously, but needing the mention of NASA
and imminent announcements about Martians to pique the curiosity of the
average Times reader.
pg