November 15, 2012
Mars Did Have Life-Supporting Water At One Time
Lee Rannals for redOrbit.com — Your Universe Online
"Rovers on Mars — the Mars Exploration rovers Spirit and Opportunity, and the Mars Science Laboratory rover Curiosity — are studying rocks to find out about the geologic history of the Red Planet," Dr John Bridges, Reader in Planetary Science in the University of Leicester Space Research Centre and lead author, said in a prepared statement. "Some of the most interesting questions are what we can find out about water, how much there was and what temperature it might have had."
According to Bridges, the meteorites from Mars found on Earth comes in there different groups, including: the shergottites, the nakhlites and the chassignites.
"Of most interest for the question of water on Mars are the nakhlites, because this group of Martian meteorites contains small veins, which are filled with minerals formed by the action of water near the surface of Mars," he said.
The team studied those alteration minerals in great detail, and found that eight nakhlite Martian meteorites all have small but significant differences between them and in their alteration minerals.
Investigations of the minerals with an electron microscope and a transmission electron microscope have revealed that the first newly formed mineral to grow along the walls of the vein was iron carbonate. This would've been formed by C02-rich water around 300 degrees Fahrenheit. When the water was cooled to 122 degrees Fahrenheit, it would have formed the clay minerals, which were followed by an amorphous phase that has the same composition as the clay.
"The mineralogical details we see tell us that there had been high carbon dioxide pressure in the veins to form the carbonates," Bridges said. "Conditions then changed to less carbon dioxide in the fluid and clay minerals formed. We have a good understanding of the conditions minerals form in but to get to the details, chemical models are needed."
Dr Susanne Schwenzer, Postdoctoral Research Associate in the Department of Physical Sciences at The Open University, who previously studied Martian meteorite compositions, said she used the findings from orbiters around Mars, and modeled each of the new minerals individually.
"Those orbiters have found clays on the surface of Mars, but the spatial resolution is very different from the detailed study achieved in the nakhlites," Schwenzer said. "Before we had the detailed study of the nakhlite meteorites, we did not know that carbonates are forming first, followed by the clays. Therefore I was very excited to see the details of the new mineralogical study."
Bridge said that the driving force heating up the water might have an impact into the Martian surface.
"And you only have to look at a map of Mars to see how numerous those are on the Martian surface," Dr. Schwenzer said in a statement.