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February 15, 2013 5:06 pm
The planet Mercury was displayed on Friday as a colourful globe with a wide variety of terrains, in a new composite view compiled from images sent from the US space agency Nasa’s Messenger spacecraft.
Messenger has been in orbit for two years around Mercury – the first time the sun’s nearest planet has had a satellite – and its observations have transformed astronomers’ views of it.
“Although its appearance is superficially similar to that of the moon, Messenger has demonstrated that Mercury is radically different from the moon in all characteristics that have been measured,” said David Blewett, a mission scientist, who unveiled new images at the annual meeting of the American Association for the Advancement of Science in Boston.
The global map uses false colour to enhance the different appearance of various materials on Mercury's surface. Young “crater rays” spreading out from fresh impact craters appear light blue or white. Darker blue areas are rich in a dark, opaque mineral, while tan areas are plains formed by the eruption of lava from the planet’s interior.
The large round area near the top is the Caloris impact basin, whose interior is filled with smooth, somewhat younger volcanic plains. Small orange spots are materials deposited by volcanic eruptions.
More detailed observations, not shown on the global image, reveal deposits of ice in places that are permanently shaded from the sun’s searing heat.
The AAAS meeting also heard that researchers at Nasa’s Jet Propulsion Laboratory in California were drawing up plans for a $2bn unmanned mission to observe Europa, a moon of Jupiter that is believed to have a large ocean of water – kept liquid by tidal heating – beneath its icy crust.
“We believe that Europa is the most likely place beyond Earth to have life in our solar system,” said Robert Pappalardo of the JPL.
Nasa and the US government have not decided whether to fund the so-called Europa Clipper mission. If it goes ahead, a craft could be launched towards Europa in 2022, on the most optimistic timetable, and arrive six years later.
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