MARS was once a wobbly planet. So propose two researchers, who say this explains evidence that glaciers once formed on mountain slopes at the planet's equator (Science, vol 311, p 368).
The problem was finding a source for the water, given that Mars appears to have been cold and dry for billions of years.
James Head of Brown University in Providence, Rhode Island and Francis Forget of the Pierre Simon Laplace Institute in Paris say it is possible if Mars, which has moons too small to stabilise it, wobbled along its rotational axis. A 45-degree tilt would point the planet's poles more towards the sun, melting the polar caps and releasing water that precipitated as snow on the slopes of low-latitude mountains.
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20:00 03 July 2008
