Mars probably never wet enough for life, nuclear bomb crater indicates

Spoilsport boffins: Theorised aliens have feet of clay

Spoilsport French scientists probing unusual clay deposits discovered in an old nuclear bomb crater say they have found that the planet Mars has never been - as previous researchers have hoped/suggested - wet enough to support Earth-style life.

Clays found on the red planet dating from its Noachian period (around four billion years ago) have a similar appearance to Earth clays created in the presence of flowing water, which has led previous scientists to believe that back then Mars was much warmer and wetter than it now is - warm and wet enough, perhaps, to support life. This naturally makes Mars a lot more interesting than it would otherwise be (though even if it has always been perishing cold and arid, it remains the most Earthlike planet that we know of for sure as yet, and has the added bonus that we can actually reach it with available technology).

Unfortunately for the possible habitability of ancient Mars, French boffins have now discovered clays not unlike Noachian ones here on Earth which were not formed by any flowing water. Rather they were created as molten lava cooled. In this case - these clays having been found at the Mururoa Atoll in French Polynesia - the lava was created during an early French atomic-weapons test.

The scientists write, in hefty boffinry journal Nature Geoscience:

The iron- and magnesium-rich clays described in thick, extensive outcrops of Noachian crust have been proposed to originate from aqueous weathering. This would imply that liquid water was stable at the surface of early Mars, presumably when the climate was warmer and wetter. Here we show that iron- and magnesium-rich clays can alternatively form by direct precipitation from residual, water-rich magma-derived fluids. Infrared reflectance spectra from terrestrial lavas from the Mururoa Atoll (French Polynesia) that underwent this precipitation process are similar to those measured for the Noachian crust.

"Mars was not as warm and wet in its earliest time as some have suggested. I do not believe in an early ocean on Mars," Professor Alain Meunier - lead author of the study - tells the Beeb.

That said, Meunier doesn't rule out possible surface Martian water at other points in its history, and other scientists still believe that such oceans, lakes or rivers may have existed at some point. Nobody is arguing that the red world is totally free of water even now: snow has been seen falling in its polar regions by robot landers, and various other previous studies have indicated water and warmth perhaps beneath the surface rather than on it, which might have offered limited habitats for life along the lines of Earth cave- or deep-ocean-dwelling lines.

We're liable to find out more on this subject in coming years following the recent arrival of NASA's robot rover Curiosity at the Gale Crater on Mars, a location specifically picked because it's a good spot (among other things) for a bit of red-clay sniffing. ®