It can fly at up to 2.5 times the speed of sound and is designed for low-altitude, high-speed, precision attacks.

BBC: News | In Depth | Military Fact Files

The probe entered a special low-altitude orbit for about five months to allow the GRAND instrument to analyze emissions from Vesta's surface that result from collisions between cosmic ray particles and elements in the asteroid's dirt.

MSN: Surprisingly, giant asteroid Vesta covered in hydrogen

"Because the maximum thickness of these small, low-altitude glaciers rarely exceeds 40 metres, with such an annual loss they will probably completely disappear within the coming decades, " said lead author Antoine Rabatel, from the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France.

BBC: Massive melting of Andes glaciers

They were most concerned with low-Earth orbit (that is, below 2, 000km in altitude).

BBC: Space debris collisions expected to rise

But high-altitude carbon emissions are reckoned to be more damaging than low-level ones, although nobody is sure by exactly how much.

ECONOMIST: Flying and climate change