Greenland's surface layer vaulted into the news in summer 2012 when higher than normal temperatures caused surface melting across about 97 percent of the ice sheet.

ENGADGET: NASA's GROVER eco-rover to examine Greenland's ice sheet (video)

About half of the route is across permafrost, which poses particular challenges because of the danger of subsidence caused by melting at the surface in summer.

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Discovery of volcanic ice flows and melting of ice on the surface of Europa that support the premise of liquid oceans underneath.

CNN: Galileo moves on to Europa

And now the Arctic's upper layers are getting less dense, for several reasons: melting Arctic glaciers, rising surface-water temperatures, increased precipitation and an absence of salt concentrations resulting from sea-ice formation.

ECONOMIST: The science

The acceleration of lift-off would not kill something that size, and if a rock is large enough, the heat generated as it is thrown clear will be negligible except at its surface where, if anything, melting may even produce an airtight skin to protect any microbes deeper down from the unpleasant vacuum of space.

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He has argued that many of the large asteroids out there could have reached a stage of partial melting - even ones that at the surface appear to be unchanged.

BBC: A fleeting encounter with an 'inbetweener'

Melting on the ice sheet's surface acts as a feedback mechanism, Dr van den Broeke explained, because the liquid water absorbs more and reflects less of the incoming solar radiation - resulting in a heating of the ice.

BBC: Greenland ice loss 'accelerating'

It includes striking examples, such as the melting glaciers of Kilimanjaro (the highest mountain in Africa) which have lost 80% of their surface area during the twentieth century due to the combined effects of climate change and human activities.

UNESCO: THEMES