Melting snow made water flow on Mars

National Geographic

In the search for life, Mars has been a bit of a let-down so far. A few decades ago everyone thought there were canals there built by little green men. It turned out that Mars’s surface features had just been misinterpreted. Then there was that famous rock half-way through the last decade that was thought to contain bacteria – it was actually a weird-shaped mineral. Then a few months ago we were told water had been seen flowing on Mars… only to discover that it was dust, not water. Oops.

But now a new discovery has raised the possibility of life existing on Mars, even if it died out long ago. Scientists have concluded that several gullies created millions of years ago were almost certainly formed by flowing water. Where did the water come from? Probably from melting snow, which started to thaw as the Martian spring began.

National GeographicLike any planet, the angle of Mars’s axis of rotation varies gradually over long periods of time. In fact, it may have reached as much as 45 degrees or more several million years ago, double its current angle of around 23 degrees. This would mean that it had more extreme seasons, which could have contributed to the thawing of the ice. Another intriguing possibility is that water somehow burst out from underground springs.

It’s all very well saying water was flowing millions of years ago, but how do we know? Basically, scientists saw that the gullies all tended to point in the same direction, which would tie in with the idea that the gullies were something to do with the Sun melting ice. The Sun would be at the same angle each spring, causing snow to melt in the same locations, carving out these gullies.

Does this latest discovery have any big implications for the hunt for life? It does raise the chances that there was once life on Mars, although it was already quite well known that Mars used to be a wetter planet. Nevertheless, every step forward in the search for life is important, and I’m hoping that this discovery will be able to pinpoint scientists to the locations where life was most likely to have existed.


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