Europe's Moon mission to scan giant crater

 作者:皇褐笥     |      日期:2019-02-26 06:05:03
By Stuart Clark Europe’s first mission to the Moon is set to scrutinise the largest crater in the Solar System, looking for a new type of Moon rock. It will also be on the lookout for landing sites so that a future robotic mission can bring samples home. ESA’s spacecraft, SMART-1 is due to launch on 3 September 2003. It will use X-rays and infrared light to map the composition of the whole Moon, including the 2000-kilometre-wide Aitken Basin. The basin sits over the Moon’s south pole and was excavated billions of years ago by the impact of a giant asteroid or comet. It is hoped the observations will give a glimpse of a never-before-seen type of Moon rock: the lunar mantle. The mantle rocks will help astronomers understand better how the Moon was formed and evolved, but sit beneath the lunar crust that was sampled by astronauts. “To reach the mantle rocks you would normally have to drill through a few tens of kilometres of crustal rock,” says Sarah Dunkin, at the Rutherford Appleton Laboratory, in Oxfordshire, UK. “In the Aitken Basin, however, we believe that a giant meteorite has done the drilling for us.” The impact was so large that calculations suggest the object must have punched its way clean through the crust to hurl mantle rocks up onto the surface. The Aitken Basin’s location on the far side of the Moon means it was only recognised as an impact structure by NASA’s Galileo spacecraft 1990. SMART-1 will be the first spaceprobe to conduct a rigorous scientific survey of this feature. Its human-eye-sized camera will also map the Aitken Basin’s topography in detail. This will help scout out potential landing sights for a robotic sample-return mission to be led by NASA some time around 2010. SMART-1 is currently at Kourou, French Guiana, awaiting its launch on an Ariane-5 rocket. It will take 15 to 18 months to reach the Moon, via a spiral trajectory. It will be powered by ion engine – a new evolution of the technology pioneered on NASA’s Deep Space 1, 1998. SMART-1, conceived as a technology demonstrator for future spacecraft, is an all-new, miniaturised and lightweight spacecraft. It only needs an engine with a thrust equivalent to blowing on your hand, to waft it to the Moon and, at two kilograms, its infrared spectrometer is 10 times lighter than any previous instrument. The mission will cost 110 million Euros, but David Southwood, director of science at ESA, says: “To do SMART-1 without all the new innovation would probably have cost half as much again.” He sees SMART-1’s tests as essential to a number of future ESA missions, including Bepi-Colombo, which will study Mercury, and Solar Orbiter,