BBC Focus Magazine

[Shadowwolf]

Mars may have been arid for more than 600 million years, making it too hostile for any life to survive on the planet's surface, according to researchers who have been carrying out the painstaking task of analysing individual particles of Martian soil. Dr Tom Pike, from Imperial College London, will discuss the team's analysis at a European Space Agency (ESA) meeting on 7 February 2012.

The researchers have spent three years analysing data on Martian soil that was collected during the 2008 NASA Phoenix mission to Mars. Phoenix touched down in the northern arctic region of the planet to search for signs that it was habitable and to analyse ice and soil on the surface.

http://www.sciencedaily.com/releases/2012/02/120203092006.htm

[M Paul Lloyd]

*sigh* thought so...................

[Lateralman]

Darn, bang goes the holiday plans.

[MikeG]

The team also estimated that the soil on Mars had been exposed to liquid water for at most 5,000 years since its formation billions of years ago.

There's a bit of a discrepancy here. One team finding that water existed in liquid form for 5,000 at most. The other estimates that water existed for billions of years, The first quote is an extract from ShadowWolfs posting.

Mouginot says an ocean first existed 4 billion years ago, when warmer conditions prevailed on Mars. A second ocean may have formed a billion years later when subsurface ice melted following a large impact, creating outflow channels that drained the water into areas of low elevation. The search for life, meanwhile, goes on.

http://www.newscientist.com/blogs/short ... otogr.html

If the second estimate is correct, that was more than enough time for rudimentary life to emerge.

[M Paul Lloyd]

Then again any underground water that may have persisted far longer than either might just have provided ideal conditions?

[Shadowwolf]

There's a bit of a discrepancy here.

Not quite, even if an ocean formed twice as the Nature article mentions, it doesn't preclude the soil only being exposed to liquid water for a span of roughly 5000 years in total because both ocean periods were short. Plus, the main point of the article I linked to was that Mars has been arid for the last 600 million years and that's why life there is unlikely. Life arising in either section of those 5000 years may be possible but it's the existence of it now that seems unlikely with such a long dry spell.

Might be different a ways below the surface but we're not there yet.

[MikeG]

You're right SW. I should have been more alert when reading this. It never stated specifically how long the oceans lasted. I just assumed that the existence of deposits implied a long period.