THE surface make-up of an object from the Kuiper Belta source of comets beyond Neptunehas come to light. The object seems to harbour methane ice and tar-like hydrocarbons, a finding that adds weight to the idea that Pluto and one of Neptune's moons began their lives as the largest objects in this deep-frozen region.
The Kuiper Belt, thought to be the source of short-period comets, contains many thousands of objects no more than a few hundred kilometres across. Because these tiny worlds are so far away, they appear extremely faint. But by taking long exposures using the 10-metre Keck Telescope in Hawaii, Robert Brown of the University of Arizona in Tucson and his colleagues have at last managed to analyse the spectrum of a Kuiper Belt object.
They report in last week's
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