Nasa spacecraft discovers water ice at Mercury poles

PanARMENIAN.Net - A Nasa spacecraft has found further tantalising evidence for the existence of water ice at Mercury's poles, BBC News reported.

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.

Scientists from the Messenger mission published findings that Mercury had been geologically active for a long period in its history.

Data from the probe shows that impact craters on the planet's surface were distorted by some geological process after they formed.

The findings, reported in Science magazine, challenge long-held views about the closest world to the Sun.

Scientists also presented a new model of Mercury's internal structure, which suggests the planet's huge inner core is encased in a shell of iron sulphide - a situation not seen on any other planet.

Messenger was launched in 2004, and entered orbit around its target in March last year. Nasa recently announced that its mission would be extended until 2013.