Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, USA.
Nature. 2010 Apr 29;464(7293):1322-3. doi: 10.1038/nature09028.
Recent observations, including the discovery in typical asteroidal orbits of objects with cometary characteristics (main-belt comets, or MBCs), have blurred the line between comets and asteroids, although so far neither ice nor organic material has been detected on the surface of an asteroid or directly proven to be an asteroidal constituent. Here we report the spectroscopic detection of water ice and organic material on the asteroid 24 Themis, a detection that has been independently confirmed. 24 Themis belongs to the same dynamical family as three of the five known MBCs, and the presence of ice on 24 Themis is strong evidence that it also is present in the MBCs. We conclude that water ice is more common on asteroids than was previously thought and may be widespread in asteroidal interiors at much smaller heliocentric distances than was previously expected.
最近的观测结果，包括在典型的小行星轨道中发现具有彗星特征的物体（主带彗星，或 MBCs），已经模糊了彗星和小行星之间的界限，尽管到目前为止，在小行星表面还没有探测到冰或有机物质，也没有直接证明它们是小行星的组成部分。在这里，我们报告了对小行星 24 忒弥斯的水冰和有机物质的光谱检测，这一检测已经得到了独立的证实。24 忒弥斯属于与五个已知 MBCs 中的三个相同的动力学家族，而在 24 忒弥斯上存在冰，这有力地证明它也存在于 MBCs 中。我们的结论是，水冰在小行星上比以前认为的更为普遍，并且可能在比以前预期的更小的日心距离内广泛存在于小行星内部。
