I am generally
convinced that wherever it becomes possible and that means over a large range
of conditions, that some form of life will arrive and lodge itself and occupy
the local niche as best it can. It is
enough that the conditions make it plausible.
That certainly was true on the surface of early mars and deep in present
Mars.
Thus seeing strong
evidence in the rocks is good news. Recall
that we are presently unable to properly detect life on Earth during the
billion or so years need for it to originally emerge. This is no simple task and the progress here
informs us of our own evaluation of ancient rocks.
These are all problems
waiting for our first true space craft able to operate at one g acceleration so we can fully explore
the solar system.
Mars Meteorite with
Odd 'Tunnels' & 'Spheres' Revives Debate Over Ancient Martian Life
By Megan Gannon, News
Editor | February 28, 2014 01:00am ET
![http://assets.pinterest.com/images/PinExt.png](file:///C:/Users/florence/AppData/Local/Temp/msohtmlclip1/01/clip_image001.png)
Credit: NASA
The discovery of tiny carbon-rich balls and
tunnels inside a Martian meteorite has once again raised the possibility that
the Red Planet was teeming with primitive life millions of years ago.
The meteorite, which
fell to Earth during the Stone Age, contains microscopic burrows and spheres
that resemble the marks microorganisms leave when they eat through rocks on
Earth, scientists report in the journal Astrobiology this month. What's more,
these features seem to have been pressed into the Mars rock before it was
hurled off the Red Planet by an impact event, the researchers add.
The authors of the new
research are not claiming they've found evidence of ancient life on Mars. In
fact, nowhere in their paper do they use the word "life." (Their
preferred term is "biotic activity.") But their findings revive the
debate about the possibility of microbes in Mars' past and highlight how much
information scientists can actually glean from Martian meteorites that end up
on Earth.
"It further
strengthens the case for past life on Mars,
but, of course, it is by no means proof," said astrobiologist
Dirk Schulze-Makuch of Washington State University, who was not
involved in the study.
Scientists haven't yet
found any solid proof that life actually existed on ancient Mars — but they
have found evidence that the planet could have been habitable. Though Mars is
barren today, scientists think water — a key ingredient for life — would have
covered its surface in the form of oceans, rivers and streams. And last year,
NASA's newest Mars rover, Curiosity, discovered the first evidence that
the Red
Planet could have supported living microbes billions of
years ago.
While Mars rovers,
landers and satellites are hunting for life-friendly conditions on the Red
Planet, scientists also can look for evidence of ancient life in Martian
meteorites that have landed on Earth.
###
![http://assets.pinterest.com/images/PinExt.png](file:///C:/Users/florence/AppData/Local/Temp/msohtmlclip1/01/clip_image001.png)
Credit: NASA
Mars meteorite mystery
The meteorite at the
center of the new study is known as Yamato 000593. The 30-lb. (14 kilograms)
rock was found by scientists with the Japanese Antarctic Research Expedition in
2000 at the Yamato Glacier in Antarctica.
Researchers believe it formed on Mars 1.3 billion years ago and was altered by
water during the Red Planet's wet past before being blasted to Earth during the
last 10,000 years.
The study's principal
investigator, Lauren White, a researcher at NASA's Jet Propulsion Laboratory in
Pasadena, Calif., said the main goal of the research was to find out whether
the tunnels and carbon-rich spherules inside the meteorite were indigenous or
the result of contamination on Earth.
"The paper isn't
really meant to identify if these features were formed from biotic or abiotic
means, but rather to discover if these features are actually Martian in
origin," White told Space.com in an email. "We compare this
meteorite, Yamato — which was discovered in Antarctica — to another
Martian meteorite, Nakhla, which fell in Egypt."
The Nakhla
meteorite dropped from the sky in 1911 in Egypt.
In 2006, scientists reported that this 1.3-billion-year-old Mars rock also had
a series of microscopic tunnels that resembled the trails of bacteria on Earth.
White said
similarities between Yamato and Nakhla strengthen the case for a Martian
origin. The team also looked at another meteorite, dubbed LEW87051, found in
1987 in Antarctica, as a control. It's unknown where this space rock came from,
but a Mars origin had been ruled out because of the rock's concentration of
oxygen isotopes.
This non-Martian
meteorite, which was exposed to the same Antarctic environment as Yamato, did
not contain any of the microscopic tunnels that were observed in both Martian
meteorites. White said this bolsters the argument that the features are
Martian, and not created by contamination, though she noted it would be
difficult to prove that any meteorite on Earth contains traces of alien life.
"To really
determine [ancient life on Mars] in a 'smoking gun' fashion we would need a
sample return mission from Mars — samples free of any contamination,"
White said.
The study authors also
wrote that they couldn't rule out the possibility that these tiny fossils are
the result of abiotic (or nonliving) processes.
"However,
textural and compositional similarities to features in terrestrial samples,
which have been interpreted as biogenic, imply the intriguing possibility that
the Martian features were formed by biotic activity," the authors wrote in
their paper.
Chris McKay of NASA's
Ames Research Center in Moffett Field, Calif., who was not involved in the
study, said he was doubtful that the scientific community would be swayed
by "textural and compositional similarities" as proof of a biological
origin.
"At the small
scales involved, shapes and compositions are not compelling indications of
function," McKay said in an email. He and other researchers who were not
involved in the study said they would need stronger evidence before the science
community could declare Martian life found.
"It would be hard
to find compelling proof of extraterrestrial life in a meteorite short of
isolating an organism that grows in the lab but does not have EarthDNA,"
McKay said.
More intriguing
evidence, McKay added, would be a set of complex biomolecules like proteins and
DNA that don't resemble anything on Earth life but are too complex to have
arisen abiotically. Schulze-Makuch also noted that a better indicator of life
on Mars would be "the presence of DNA, some other nucleic acid or organic
macromolecules that could be a breakdown product of a nucleic acid associated
with these microfeatures."
Astrobiologist Louisa
Preston of the U.K.'s Open University said the authors of the study "have
done well not to cry wolf and to scientifically speculate on the tubules'
origins, accepting that, as of yet, they do not know whether they are of
biological origin or not."
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