[meteorite-list] Scientists Discover How Atmosphere of Mars Turned To Stone

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 22 Oct 2013 14:59:20 -0700 (PDT)
Message-ID: <201310222159.r9MLxKvR021032_at_zagami.jpl.nasa.gov>

http://www.gla.ac.uk/news/headline_293811_en.html

Scientists discover how the atmosphere of Mars turned to stone
University of Glasgow
October 21, 2013

Scientists at the Scottish Universities Environmental Research Centre,
the University of Glasgow and the Natural History Museum in London may
have discovered how Mars lost its early carbon dioxide-rich atmosphere
to become the cold and arid planet we know today. This research provides
the first direct evidence from Mars of a process, called "carbonation"
which currently removes carbon dioxide from our own atmosphere, potentially
combating climate change on Earth.

It is widely recognised that accumulation of carbon dioxide in the Earth's
atmosphere is contributing to global warming. The loss of carbon dioxide
from the atmosphere of Mars, however, around 4000 million years ago is
likely to have caused the planet to cool. So understanding how carbon
dioxide was removed from the Martian atmosphere could lead to new ways
of reducing the accumulation of greenhouse gases in our own atmosphere.

[Image]
This image is a false colour image of the Lafayette meteorite (sample
code: USNM 1505-5) from a scanning electron microscope showing evidence
of carbonation, with siderite (orange) replacing olivine (blue).

In a paper published in the journal Nature Communications, the research
team describe analyses of a Martian meteorite known as Lafayette, sourced
from the research collections of the Natural History Museum in London
and the Smithsonian Institution in Washington. It formed from molten rock
around 1300 million years ago, and was blasted from the surface of Mars
by a massive impact 11 million years ago. Since its discovery in Indiana,
USA, in 1931, Lafayette has been studied by scientists around the world.

This research focused on a carbon-rich mineral called siderite. Although
found in Lafayette previously, the team discovered that the siderite had
formed by the process of "carbonation", whereby water and carbon dioxide
from the Martian atmosphere reacted with rocks containing the mineral
olivine. These reactions then formed siderite crystals, replacing the
olivine, and in so doing captured the atmospheric carbon dioxide and
permanently stored it within the rock.

Lafayette provides direct evidence for storage of carbon dioxide in the
fairly recent history of Mars, some time after 1300 million years. However
as all of the ingredients for carbonation were present on early Mars,
in the form of olivine, water and carbon dioxide, this reaction may explain
how carbon dioxide was removed from the planet's atmosphere changing its
climate from warm, wet and hospitable to life, to cold, dry and hostile.

Whilst this process also occurs naturally on Earth, and is the focus of
research examining methods of permanently locking up carbon dioxide from
power stations, the magnitude of the effect on early Mars indicates that
it has the potential to be effective on a planetary scale.

Dr Tim Tomkinson of the Scottish Universities Environmental Research Centre,
Research Associate at the University of Glasgow and lead author of the
paper, said "Mars once had a thick atmosphere that was rich in water and
carbon dioxide, and so this process of carbonation may help answer the
mystery of why the Martian climate deteriorated around 4000 million years
ago."

"This discovery is both significant in terms of the way in which scientists
will study Mars in the future but also to providing us with vital clues
to how we can limit the accumulation of carbon dioxide in the Earth's
atmosphere and so reduce climate change."

Dr Caroline Smith, Curator of Meteorites at London's Natural History Museum,
and co-author of the paper said, "Our findings show just how valuable
meteorites from Museum collections like those we have here at the Natural
History Museum really are. There is so much important and useful scientific
information locked away in these rare rocks. Our study shows that as we
learn more about our planetary next door neighbour, we are seeing more
and more similarities with geological processes on Earth."
Received on Tue 22 Oct 2013 05:59:20 PM PDT