Salt shakes up life debate on Mars

Last month salt was the villain in the on again, off again debate about the possibility that life may once have existed on Mars. Then it was a case of too much salt, but recent observations from the orbiting Mars Odyssey probe have uncovered chloride salts at more than 200 locations in the Red Planet’s southern hemisphere and this time it seems to be the right kind of salt. No mention is made of the earlier negative results obtained by the Opportunity Rover, and the reports, carried by publications such as the British Times newspaper and National Geographic are extremely upbeat for the case that these deposits are prime sites for life to have taken hold. Paul Knauth, a geologist at Arizona State University is reported to be particularly excited about the discovery, and has gone so far as to say that some of the 3.8 billion year old deposits may still yet be "actively oozing." An excellent article goes into depth regarding this theory at National Geographic.

Massive water deposits spotted on Mars

Evidence presented at the 39th Lunar and Planetary Science Conference here in Houston, Texas indicates that significant volumes of water ice have been discovered in Mars' mid-northern latitudes. The Sharad radar experiment on Nasa's Mars Reconnaissance Orbiter (MRO) has been looking at distinctive geological features called lobate debris aprons (LDAs). These dome-shaped structures are concentrated around the mid-latitudes in the planet's northern and southern hemispheres. By penetrating the domes with the Sharad radar, scientists were able to judge their geological makeup. Very little attenuation (reduction in signal strength) was detected, suggesting they were predominantly made of ice. Commenting on the likely concentration of water bound up in the features, lead scientist Dr Jeff Plaut estimated, "robustly, more than 50% ice by volume - but it could be much more." The ice is thought to have formed during the mid to late Amazonian era, the cold, dry period of Martian history which began around 1.8 billion years ago and lasts to the present day.

Holden crater - cup of life?

It may have have only held water for a few thousand years, but evidence gathered by the High Resolution Imaging Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter may well show that life had a chance of finding a foothold in Holden crater. The HiRise camera has spotted a jumble of house-sized rocks, called megabreccia, in the 154-kilometre-wide Holden Crater. They were probably formed in the impact that created the crater, but a spectrometer on MRO, called CRISM has discovered that the rocks are covered by layers of fine sediments and clay. Such material forms through prolonged contact with water. The evidence points to two wet periods in the history of the crater. The first would have lasted several thousands years, then later water from a network of large channels called the Uzboi Vallis system inundated the surrounding landscape. The crater wall held back the water for a time, before it rose high enough to flood the interior. This wet period would have lasted several hundred years, but it was this rapid flood that scattered the megabreccia and exposed clay that had been covered over by sediments from the first lake. Holden crater is one of 6 prime landing sites under consideration for the 2009 Mars Science Laboratory, and this discovery is sure to increase its chances of selection.