A team of scientists at the University of Glasgow and the Scottish Universities Environmental Research Centre and the Natural History Museum (London) have discovered the first evidence of water dissolving the surface of Mars. In a paper published in the Meteoritical Society's journal MAPS, the research team outline the results of tests on a 1.7-gram fragment of a Martian meteorite known as Nakhla, which was provided by the Natural History Museum.
Nakhla, named after the town in Egypt where it landed in 1911 after
being blasted from the surface of Mars by a massive impact around 10
million years ago, has been studied for decades by scientists around the
world.
Previous research on Nakhla has provided evidence of the existence of
water on Mars through the presence in the meteorite of 'secondary
minerals' – types of carbonates, hydrous silicates and sulfates most
likely formed when Martian minerals reacted with liquid water.
"What has been unclear in the past is exactly where the chemical
elements which made up the secondary minerals within Nakhla came from,"
said Martin Lee of the University's School of Geographical and Earth
Sciences, lead author of the paper. "Using a scanning electron
microscope, we examined many tiny bowl-shaped depressions, known as etch
pits, in grains of the minerals olivine and augite found in the
meteorite.
"What we've found for the first time is evidence that the etch pits
were created when water dissolved the olivine and augite, and that the
elements released from those minerals led to the formation of the
secondary minerals. It's an exciting discovery and better informs of our
understanding of how water affected rock on Mars."
By examining the amount of dissolution which occurred in the etch
pits (image below) formed within the minerals, the team have also been
able to estimate how long the water was present within the sample.
"From the amount of dissolution we observed, it's likely that this
particular piece of Mars was affected by water for only a few months and
probably less than a year in total," Lee added. "That's certainly not
long enough to sustain a life-supporting biosphere; however, the
findings of our study are from a tiny piece of a very small chunk of the
surface of Mars, so it's difficult to draw any large-scale conclusions
about the presence of water on the planet or its implications for life.
"Our research does raise fascinating questions about exactly how long
ago the water interacted with the part of Mars which Nakhla came from
and where the water might have gone. We'll be continuing to look for
clues to the answers to these questions in future research. Results from
NASA's Curiosity rover, currently on the surface of Mars, will also help us build a clearer picture of the history of Martian water."
Image at the top of the page shows a 50-kilometer-wide impact crater from ESA’s Mars Express photo of Meridiani Planum on Mars.
For more information: The paper, entitled 'Evidence for silicate dissolution on Mars from the Nakhla meteorite',
is published in MAPS and is available as an early view online
publication at onlinelibrary.wiley.com/doi/10.1111/maps.12053/pdf.
Source: The Daily Galaxy via University of Glasgow
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