Thursday, December 18, 2008

Martian Carbonates Suggest Past Life on Mars

A research team has found evidence of a long-sought carbonates that shows Mars was home to a variety of watery environments, including regional pockets of neutral or alkaline water.

Recent observations from the Mars Phoenix lander has pointed to a period when clay-rich minerals were formed by water, followed by a drier time, when salt-rich, acidic water affected much of the planet. The presence of carbonates indicates that Mars had neutral to alkaline waters when the minerals formed in the midlatitude region more than 3.6 billion years ago.

“Primitive life would have liked it,” said Bethany Ehlmann, “It’s not too hot or too cold. It’s not too acidic. It's a ‘just right’ place.’

The carbonates showed up in the most detail in two-dozen images beamed back by the Compact Reconnaissance Imaging Spectrometer for Mars, an instrument aboard the NASA Mars Reconnaissance Orbiter. Scientists found the mineral near a trough system called Nili Fossae, which is 667 km long, at the edge of the Isidis impact basin. Carbonates were seen in a variety of terrains, including the sides of eroded mesas, sedimentary rocks within Jezero crater and rocks exposed on the sides of valleys in the crater’s watershed. The researchers also found traces of carbonates in Terra Tyrrhena and in Libya Montes.

The carbonates may have been formed by slightly heated groundwater percolating through fractures in olivine-rich rocks. Or, they may have been formed at the surface when olivine-rich rocks were exposed and altered by running water. Yet another theory is the carbonates precipitated in small, shallow lakes. Either way, such environments would have boded well for primitive life forms to emerge.

“We know there’s been water all over the place, but how frequently have the conditions been hospitable for life?” Mustard said. “We can say pretty confidently that when water was present in the places we looked at, it would have been a happy, pleasant environment for life.” press release
Ref: Orbital Identification of Carbonate-Bearing Rocks on Mars. 2008. Bethany L. Ehlmann, et al. Science 322: 1828 - 1832