[meteorite-list] Life on Mars? (Again) Tissint

From: David R. Vann <drvann_at_meteoritecentral.com>
Date: Thu, 4 Dec 2014 10:52:11 -0500
Message-ID: <076b01d00fda$449643d0$cdc2cb70$_at_sas.upenn.edu>

Thought this might be of interest:
This is from "Laboratory Equipment", but it is making the rounds of such
rags. Let's see if I beat Paul H. on this one. ;)
If you are interested in the original article, and do not have access,
please contact me off-list.

Did Mars ever have life? Does it still? A meteorite from Mars has reignited
the old debate. An international team that includes scientists from EPFL has
published a paper in the scientific journal Meteoritics and Planetary
Sciences, showing that Martian life is more probable than previously
thought.
"So far, there is no other theory that we find more compelling," says
Philippe Gillet, director of EPFL's Earth and Planetary Sciences Laboratory.
He and his colleagues from China, Japan and Germany performed a detailed
analysis of organic carbon traces from a Martian meteorite, and have
concluded that they have a very probable biological origin. The scientists
argue that carbon could have been deposited into the fissures of the rock
when it was still on Mars by the infiltration of fluid that was rich in
organic matter.
Ejected from Mars after an asteroid crashed on its surface, the meteorite,
named Tissint, fell on the Moroccan desert on July 18, 2011, in view of
several eyewitnesses. Upon examination, the alien rock was found to have
small fissures that were filled with carbon-containing matter. Several
research teams have already shown that this component is organic in nature.
But they are still debating where the carbon came from.
Maybe biological, but not from our planet
Chemical, microscopic and isotope analysis of the carbon material led the
researchers to several possible explanations of its origin. They established
characteristics that unequivocally excluded a terrestrial origin, and showed
that the carbon content were deposited in the Tissint's fissures before it
left Mars.
The researchers challenged previously described views (Steele et al.,
Science, 2012) proposing that the carbon traces originated through the
high-temperature crystallization of magma. According to the new study, a
more likely explanation is that liquids containing organic compounds of
biological origin infiltrated Tissint's "mother" rock at low temperatures,
near the Martian surface.
These conclusions are supported by several intrinsic properties of the
meteorite's carbon, e.g. its ratio of carbon-13 to carbon-12. This was found
to be significantly lower than the ratio of carbon-13 in the CO2 of Mars's
atmosphere, previously measured by the Phoenix and Curiosity rovers.
Moreover, the difference between these ratios corresponds perfectly with
what is observed on Earth between a piece of coal - which is biological in
origin - and the carbon in the atmosphere. The researchers note that this
organic matter could also have been brought to Mars when very primitive
meteorites - carbonated chondrites - fell on it. However, they consider this
scenario unlikely because such meteorites contain very low concentrations of
organic matter.
"Insisting on certainty is unwise, particularly on such a sensitive topic,"
warns Gillet. "I'm completely open to the possibility that other studies
might contradict our findings. However, our conclusions are such that they
will rekindle the debate as to the possible existence of biological activity
on Mars - at least in the past."

David R. Vann, Ph.D.
Department of Earth and Environmental Science
The University of Pennsylvania
240 S. 33rd St.
Philadelphia, PA 19104
Received on Thu 04 Dec 2014 10:52:11 AM PST