SPACE FOSSILS:
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Space Fossils 3 of 16
On Dec. 27, 1984 meteorite hunters found a meteorite fragment in
Allan Hills, Antarctica that they believed to be of Martian origin (yes
you read that right, but wait it gets weirder). Twelve years later in
1996 scientists studying the rock under an electron microscope found
evidence that this was actually fossil evidence of extraterrestrial
bacteria. This has provoked many experts to entertain the theory that
life as we know it did not originate on Earth but could have been
brought to Earth by falling space rocks.
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A Martian meteorite is a rock that formed on the planet Mars and was then ejected from Mars by the impact of an asteroid or comet, and finally landed on the Earth. Of over 61,000 meteorites that have been found on Earth, 132 were identified as Martian as of 3 March 2014.[1]
These meteorites are thought to be from Mars because they have
elemental and isotopic compositions that are similar to rocks and
atmosphere gases analyzed by spacecraft on Mars.[3] On October 17, 2013, NASA reported, based on analysis of argon in the Martian atmosphere by the Mars Curiosity rover, that certain meteorites found on Earth thought to be from Mars were indeed from Mars.[4]
The term does not refer to meteorites found on Mars, such as Heat Shield Rock.
On January 3, 2013, NASA reported that a meteorite, named NWA 7034 (nicknamed "Black Beauty"), found in 2011 in the Sahara desert, was determined to be from Mars and found to contain ten times the water of other Mars meteorites found on Earth.[2] The meteorite was determined to have formed 2.1 billion years ago during the Amazonian geologic period on Mars. |
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Filaments in the
Orgueil meteorite, seen under a scanning electron microscope, could be
evidence of extraterrestrial bacteria, claims NASA scientist Richard
Hoover. |
The finding
Astrobiologist Richard Hoover of NASA's Marshall Space Flight Center in
Huntsville, Ala., used scanning electron microscopes to analyze slices
of carbonaceous meteorites that fell to Earth from space.
Based on the appearance of "filaments" and other features that resemble
microbes, Hoover argues that the meteorites contain fossilized life in
the form of
cyanobacteria
– single-celled organisms also known as blue-green algae. He supports
this claim by presenting evidence of chemical compounds present in the
meteorites that are consistent with a biological origin.
Hoover writes that the "the size, structure, detailed morphological
characteristics and chemical compositions of the meteorite filaments are
not consistent with known species of minerals," and that they must be
evidence of single-celled life in the rocks.
If true, the discovery would mean
life in the universe
is not unique to planet Earth – that it may have sprouted up multiple
times in other locations, or even that Earth's life originated in space
and was deposited on the planet by meteorites.
"Because this would be a very important result if true, scientists are going to do what they
should do:
be skeptical," said astronomer Seth Shostak of the Search for
Extraterrestrial Intelligence (SETI) Institute in Mountain View, Calif.
The reaction
Shostak called the paper "an extensive and thorough review" of Hoover's
findings, but said they did not amount to convincing evidence.
"If you look at the microscope photos, they are certainly suggestive –
looking like photos made of various terrestrial bacteria," Shostak told
SPACE.com. "But then again, while intriguing, that's hardly proof. If
similarity in appearance were all it took to prove similarity in kind,
then it would be pretty easy for me to demonstrate that there are big
animals living in the sky, because I see clouds that look like them."
The same goes for the chemical evidence Hoover presents, Shostak said. While these compounds could have been produced by
microbial life, they also could have been made by non-biological, mundane processes.
The type of microbe Hoover claims to have discovered has also provoked some scientists' skepticism.
Cyanobacteria live in liquid water and are
photosynthetic,
meaning they convert carbon dioxide into organic compounds using energy
from sunlight. That implies that the meteorites would have had to
contain liquid water exposed to sunlight, and also that high
concentrations of oxygen would be present, said astrobiologist Chris
McKay of NASA's Ames Research Center in Moffett Field, Calif.
Such a scenario is unlikely based on researchers' current understanding
of meteorites, McKay said. If they contain liquid water at all, it is
likely in their interior, not on the surface, where it would be in
contact with sunlight.
McKay said Hoover's findings suggest that either the filaments in the
microscopic images are chance shapes, or that the environments on
meteorites were much different than scientists expect.
He expressed respect for the overall methods of the study, and said
Hoover had presented enough evidence that the structures present do come
from the meteorites and weren't introduced as contamination after the
rocks landed on Earth.
"Richard Hoover is a careful and accomplished microscopist, so there is
every reason to believe that the structures he sees are present and are
not due to contamination," McKay wrote in an e-mail to SPACE.com.
Questioning the journal
As soon as word of the paper was announced, some scientists were
reluctant to give it credence based on the Journal of Cosmology's
reputation.
"It isn't a real science journal at all, but is the ginned-up website
of a small group of crank academics obsessed with the idea of [Fred]
Hoyle and [Chandra] Wickramasinghe that life originated in outer space
and simply rained down on Earth," P.Z. Myers, a biologist at the
University of Minnesota, Morris, wrote on his popular science blog
Pharyngula. "It doesn't exist in print, consists entirely of a crude and
ugly website that looks like it was sucked through a wormhole from the
1990s, and publishes lots of empty noise with no substantial editorial
restraint."
Myers also referred to the paper as "garbage."
Rosie Redfield, a microbiologist at the University of British Columbia,
questioned whether the journal's papers are really peer-reviewed, as it
claims.
"The journal proudly announces that it is obtaining and will publish
100 post-publication reviews," she wrote on her blog, RRResearch. "But
did it bother getting any pre-publication reviews? It will be shutting
down in a few months, after only two years of online publication (the 13
'volumes' are really just 13 issues). Its presentation standards are
pretty bad – there doesn't seem to have been any effort at copy-editing
or formatting the text for publication (not even any page numbers)."
NASA confirmed that the paper had not been peer-reviewed.
"NASA cannot stand behind or support a scientific claim unless it has
been peer-reviewed or thoroughly examined by other qualified experts,"
Paul Hertz, chief scientist of NASA’s Science Mission Directorate in
Washington, D.C., said in a statement. "This paper was submitted in 2007
to the International Journal of Astrobiology. However, the peer review
process was not completed for that submission."
Some scientists approached about the paper asked not to comment officially but said the research didn't merit attention.
The editors of the Journal of Cosmology dismissed such attacks as
"tantamount to school-yard taunts by jealous children," in a follow-up
press release after the paper's announcement.
In response to some critics questioning why the research wasn't
published in the more prestigious journals Science or Nature, the
Journal of Cosmology responded with a statement that "both Science and
Nature have a nasty history of rejecting extremely important papers,
some of which later earned the authors a Nobel Prize."
"Science and Nature are in the business of making money," the journal
charged. "The Journal of Cosmology, is free, open access, and is in the
business of promoting science."
We've seen this before
This is not the first time that a debate has raged over possible evidence for life in meteorites.
In 1996, researchers made a splash when they announced evidence for fossilized microbial life in a meteorite from Mars called
Allan Hills 84001
(ALH 84001). The lead author of the paper announcing these findings in
the journal Science was David McKay, a researcher at NASA's Johnson
Space Center (not to be confused with NASA Ames' Chris McKay).The claim
prompted giant headlines in papers around the world at the time, and
even a statement from President Bill Clinton.
But in the years since, scientists have questioned those findings — and
most remain unconvinced that the meteorite offers conclusive evidence.
"Prior claims for evidence of microfossils in ALH 84001 remain
controversial at best, despite more than a decade of dedicated research
by many groups and dozens of scientific papers on the subject," said
planetary geologist Victoria Hamilton of the Southwest Research
Institute in Boulder, Colo. "I'm skeptical that these new claims will be
any less controversial or any more easily proven or falsified."
Shostak said wariness after the Allan Hills controversy could be carrying over to this announcement.
"The ALH 84001 result was based on photos and chemical evidence, much
as the current story," Shostak said. "And I think that's a major part of
the reason why many experts in this field are skeptical of Hoover's
claim to have found life that cooked up in comets."
Ultimately, this find, like the Allan Hills report, isn't enough to settle the score one way or the other.
"Sometimes scientific results are ambiguous, and are greeted with the
common (and rather uninspiring) refrain that 'more research is needed,'"
Shostak said. "That's the case here. We need evidence from other
approaches and from other researchers."