MERCURY POLES GIVE UP HINTS OF WATER ICE.

by WhiteKnight, UK, Thursday, March 22, 2012, 07:27

Mercury poles give up hints of water ice

Messenger map of Mercury poles Nasa/JHUAPL/Carnegie Institution The radar-bright patches line up perfectly with areas of permanent shadow

The radar-bright patches line up perfectly with areas of permanent shadow

A Nasa spacecraft has found further tantalising evidence for the existence of water ice at Mercury's poles.

Though surface temperatures can soar above 400C, some craters at Mercury's poles are permanently in shadow, turning them into so-called cold traps.

Previous work has revealed patches near Mercury's poles that strongly reflect radar - a characteristic of ice.

Now, the Messenger probe has shown that these "radar-bright" patches line up precisely with the shadowed craters.

Messenger is only the second spacecraft - after Mariner 10 in the 1970s - to have visited the innermost planet. Until Messenger arrived, large swathes of Mercury's surface had never been mapped.

The bright patches were detected by ground-based radio telescopes in the 1990s, but as co-author Dr Nancy Chabot explained, "we've never had the imagery available before to see the surface where these radar-bright features are located."

The researchers superimposed observations of radar bright patches by the Arecibo Observatory on the latest photos of Mercury's poles taken by the MDIS imaging instrument aboard Messenger.

"MDIS images show that all the radar-bright features near Mercury's south pole are located in areas of permanent shadow," said Dr Chabot, from Johns Hopkins University Applied Physics Laboratory (JHUAPL).

"Near Mercury's north pole such deposits are also seen only in shadowed regions, results consistent with the water-ice hypothesis."

However, she cautions, this does not constitute proof, and for many craters, icy deposits would need to be covered by a thin layer (10-20cm) of insulating debris in order to remain stable.

Maria Zuber, from the Massachusetts Institute of Technology (MIT), who is a co-investigator on the Messenger mission, told BBC News: "The most interesting interpretation of [the radar observations] is that they were due to water ice
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