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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
9 L1 e' P" U& O5 A' r/ S" u( ha lower density of craters smaller than about 100 km in diameter than on the
( I3 {+ q( X7 x: S5 P7 R+ UMoon, a deficit that has been attributed to resurfacing by formation of ancient
2 E4 u z! i+ O) B8 H, P6 @intercrater plains. Simone Marchi et al. used a crater areal density map
, ?3 O5 @$ d$ b1 qbased on data from the MESSENGER spacecraft (the colour-coded foreground on 6 Y# H& g4 j# M4 S4 f
cover, with a global surface mosaic in the background) to locate the oldest
! X% Z M1 a' N9 a6 ~# ksurfaces on Mercury and interpret the crater populations in the framework of a . I& {6 _- ^7 r
recent lunar crater chronology. They conclude that the oldest surfaces were & ~# X1 {" n) Q# Z0 Y% K
emplaced just after the start of the Late Heavy Bombardment 4.0 to 4.1 billion : r' P1 H8 v5 T( f
years ago. The large impact basins, not previously dated, yield a similar
9 \' l2 ]3 f' lsurface age. This agreement implies that resurfacing was global and due to h, D6 H1 }& z* m( ^2 i' [8 _3 ?
volcanism, perhaps aided by heavy bombardment as previously suggested. Cover: - _$ ~+ a" G7 C% ?5 b6 S2 g; v+ m; w
Simone Marchi/MESSENGER data: NASA/JHUAPL/Carnegie Institution of Washington& ~: Y& r0 `6 ], F$ I
x+ H8 [2 t# R$ G
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发表于 2013-7-5 23:43
发表于 2013-7-6 08:19
