Golden probe

日期:2019-03-07 04:09:06 作者:干嘴比 阅读:

By Jon Copley IF THERE is an ocean on Jupiter’s moon Europa, any probe sent to explore it will need to be gold-plated to avoid corrosion, say astronomers who have found sulphuric acid lurking in the moon’s icy crust. Europa’s surface consists mainly of water ice, but observations from a spectrometer on the Galileo spacecraft hint that there are other minerals there too. Bob Carlson of NASA’s Jet Propulsion Laboratory in Pasadena, California, hoped to make a chemical mix that resembles conditions on Europa. They found that the infrared spectrum of sulphuric acid most closely matches the pattern Galileo saw (Science, vol 286, p 97). The team suggests that the acid is there thanks to Europa’s neighbour Io, which belches sulphur from its volcanoes. The sulphur forms an atmosphere around Io, then is ionised and whipped away by Jupiter’s magnetosphere. When the ions hit Europa, they react with hydrogen peroxide in the ice to form sulphuric acid. “Sulphuric acid, sulphur polymers and sulphur dioxide are part of a continuing cycle on Europa’s surface,” says Carlson. “Most of the sulphur exists as sulphuric acid because it is the most stable.” Although this process occurs on the moon’s surface, Carlson believes the acid could be pushed down into the ocean that may lie beneath the icy surface ( New Scientist, 18 September, p 41). Sulphur may also come from Europa’s interior, an idea proposed by Jeff Kargel of the US Geological Survey in Flagstaff, Arizona. “We don’t know the concentration of sulphuric acid that might occur in the ocean, but it could be fairly corrosive,” says Carlson. The acid in his experiment was concentrated enough to corrode lab equipment. “I’d use nonreactive coatings for any probes,