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- 积分
- 17983
- 威望
- 17983
- 包包
- 26159
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The most heavily cratered terrains on Mercury exhibit
3 Z- F0 o! \1 Y& {1 l( x5 V0 |/ ]a lower density of craters smaller than about 100 km in diameter than on the 5 m+ \/ `1 J$ n6 \
Moon, a deficit that has been attributed to resurfacing by formation of ancient ; @% U/ n7 v0 m6 I# X7 D# D
intercrater plains. Simone Marchi et al. used a crater areal density map
# w0 H* B5 D. T, I$ o, sbased on data from the MESSENGER spacecraft (the colour-coded foreground on 3 H. |5 G" r- }1 U8 v1 n. w- L
cover, with a global surface mosaic in the background) to locate the oldest 9 F" r. p, p r0 ?5 k
surfaces on Mercury and interpret the crater populations in the framework of a ' D+ [& m' ?" z/ }
recent lunar crater chronology. They conclude that the oldest surfaces were
9 M) b2 l* L5 p% M! Y1 Pemplaced just after the start of the Late Heavy Bombardment 4.0 to 4.1 billion ; G9 ]1 f5 A$ ~; p9 Z! L
years ago. The large impact basins, not previously dated, yield a similar
, |/ z% K* A1 y {5 @. v9 psurface age. This agreement implies that resurfacing was global and due to
$ {* [% L% Y8 p) \ ]! h3 Cvolcanism, perhaps aided by heavy bombardment as previously suggested. Cover:
8 w5 e1 S9 H4 H" Q" N0 tSimone Marchi/MESSENGER data: NASA/JHUAPL/Carnegie Institution of Washington
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发表于 2013-7-5 23:43
发表于 2013-7-6 08:19
