Learning English - Words in the News
04 August, 2004 - Published 10:48 GMT
Space mission to Mercury
The American space agency, NASA, has launched an unmanned probe, named Messenger, that will travel to Mercury, the closest planet to the Sun. Its journey will take almost seven years and cover a distance of eight billion kilometres. This report from Tracey Logan:
Almost thirty years ago, NASA's Mariner Ten spacecraft took the most recent pictures we have of Mercury, revealing a rocky surface - wrinkled like an old apple. It found a planet of extremes, with surface temperatures reaching five hundred degrees Celsius and shady crevices plummeting to minus two hundred. Later observations seemed to show ice there - one of the things Messenger will search for.
Circling the planet for a full year, instruments on board Messenger will seek to solve other mysteries on Mercury. Why is its iron core so big, for instance? Where does its Earth-like magnetic field come from? And where did those wrinkles - actually kilometre-high cliffs stretching hundreds of kilometres across the surface - come from?
Despite the absence of a lander, Messenger will learn much about the internal workings of this strange planet. Solving its riddles will help understand how Mercury formed, along with its rocky neighbours, Venus, Mars and our own planet - Earth.
Tracey Logan, BBC
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