Nasa's Messenger spacecraft to crash into Mercury, ending mission
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Version 0 of 1. Mercury, the innermost planet of the solar system, will acquire a fresh crater on Thursday when a half-tonne US spacecraft slams into the planet’s surface to end its spectacular four-year mission. The Messenger probe launched from Earth in 2004 and has been mapping Mercury in exquisite detail since it arrived in orbit in 2011. The spacecraft has beamed back a series of breathtaking images of the tiny, scorched world, which orbits so close to the sun that daytime temperatures reach 427 Celsius. Mercury swings around the sun at an average distance of 36m miles, much closer than Earth, which orbits at a distance of about 93m miles. Related: Mercury's 'dynamic and complex world' revealed by Nasa's Messenger “Messenger has been an amazing mission. The only previous Mercury mission, Mariner 10, flew post the planet three times in 1974 and 1975 giving us only an incomplete view. Messenger revealed the whole globe in detail,” said David Rothery, professor of planetary geosciences at The Open University. The spacecraft is close to running out of fuel and is expected to crash into the surface of the planet at 8,750 miles per hour on Thursday at 8.30pm UK time. Nasa scientists said the probe would crash into the far side of Mercury, beyond the view of ground-based telescopes. The space agency will only confirm that the impact has taken place when Messenger fails to reappear hours later. John Grunsfeld, associate administrator for the science mission directorate at Nasa’s HQ in Washington said: “While spacecraft operations will end, we are celebrating Messenger as more than a successful mission. It’s the beginning of a longer journey to analyse the data that reveals all the scientific mysteries of Mercury.” Data beamed back from the spacecraft suggest that large quantities of frozen water – enough to cover Washington DC in a two mile thick layer of ice – lie in Mercury’s permanently shadowed polar craters. The surface of the ice is tainted with dark patches that are thought to be organic compounds. “It is now apparent that Mercury is a misfit planet that seems not to belong where we now find it. It is dense even for a rocky planet, showing that its iron-rich core occupies more than 80% of Mercury’s radius,” said Rothery. “The outer part of the core must still be molten, because this is where Mercury’s magnetic field is generated – a characteristic shared with the Earth, but not with Venus, Mars or the Moon.” Images from Messenger have revealed signs of recent volcanic eruptions blasting upwards through Mercury’s ancient lava fields. Others point to mysterious “hollows”, which are steep, flat-bottomed depressions in the planet where the top 10 metres or so of the surface are missing. “Airless Mercury has no wind to blow it away, and there are no signs of collapse into underground cavities, so we are forced to conclude that something in the ground has been turned to vapour and lost to space,” Rothery said. |