Differentiation of the asteroid Ceresas revealed by its shape

被引:200
作者
Thomas, PC [1 ]
Parker, JW
McFadden, LA
Russell, CT
Stern, SA
Sykes, MV
Young, EF
机构
[1] Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA
[2] SwRI, Dept Space Studies, Boulder, CO 80302 USA
[3] Univ Maryland, Dept Astron, College Pk, MD 20742 USA
[4] Univ Calif Los Angeles, IGPP & ESS, Los Angeles, CA 90095 USA
[5] Planetary Sci Inst, Tucson, AZ 85719 USA
基金
美国国家航空航天局;
关键词
D O I
10.1038/nature03938
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The accretion of bodies in the asteroid belt was halted nearly 4.6 billion years ago by the gravitational influence of the newly formed giant planet Jupiter. The asteroid belt therefore preserves a record of both this earliest epoch of Solar System formation and variation of conditions within the solar nebula. Spectral features in reflected sunlight indicate that some asteroids have experienced sufficient thermal evolution to differentiate into layered structures(1). The second most massive asteroid - 4 Vesta - has differentiated to a crust, mantle and core(2,3). 1 Ceres, the largest and most massive asteroid, has in contrast been presumed to be homogeneous, in part because of its low density, low albedo and relatively featureless visible reflectance spectrum, similar to carbonaceous meteorites that have suffered minimal thermal processing(4). Here we show that Ceres has a shape and smoothness indicative of a gravitationally relaxed object. Its shape is significantly less flattened than that expected for a homogeneous object, but is consistent with a central mass concentration indicative of differentiation. Possible interior configurations include water-ice-rich mantles over a rocky core.
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页码:224 / 226
页数:3
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