While Mars shows off its rusty face in Earth鈥檚 skies, making its close approach to within 67 million kilometres of our planet, new images show further evidence of near-surface ice on the Red Planet.
Images captured by the Mars Orbiter Camera (MOC) suggest that ground ice was present 10 million years ago. On a geological time scale, this is very recent.
The ice deposits were near Mars鈥� equator and are probably no more than five metres below the planetary surface. Being near the equator makes them accessible to exploration, as conditions there are less harsh.
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鈥淚f ground ice was present within five metres of the surface only a few million years ago, it is very likely to persist today within about the upper 10 metres,鈥� says Alfred McEwen from the University of Arizona.
Exactly where the ice came from is not known. It could have been left over from the planet鈥檚 formation, recondensed from atmospheric water vapour or recharged by surface flooding.
Cones ahead
The MOC images show Martian cones, similar in shape and size to the 鈥渞ootless鈥� cones of Iceland, in clusters of tens or many hundreds.
Rootless cones, or pseudocraters, form when hot lava meets with volatile substances such as water or carbon dioxide. The resulting explosion creates cones at the surface, with lava tubes flowing below.
Psuedocraters can also form when a sudden weight such as sediment presses down on volatiles. However, Dave Rothery from the Open University at Milton Keynes believes the researchers are right: 鈥淚n these examples, the cones do look like they are on lava flows.鈥�
Pseudocraters may also be possible further around the planet, but they appear to be in curved lines rather than being dotted about. When the British-led Martian lander Beagle 2 touches down in late 2003, scientists hope to gain an understanding of these cones.
鈥淭he evidence is mounting up,鈥� says Rothery. 鈥淚t looks like we鈥檝e got volatiles on Mars.鈥�
More at: Geophysical Review Letters (vol 28, p 2365)