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- 积分
- 17983
- 威望
- 17983
- 包包
- 26159
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7 D0 N3 S: H5 N$ n+ r* Y2 ]% P" RThe most heavily cratered terrains on Mercury exhibit , _7 S. A$ `' E+ P) s+ c& F8 U8 H
a lower density of craters smaller than about 100 km in diameter than on the ( G$ T) R$ l; x+ Z& v6 v
Moon, a deficit that has been attributed to resurfacing by formation of ancient
- W# x7 U e5 u( J; D' ointercrater plains. Simone Marchi et al. used a crater areal density map
% i r6 A% @ r/ c- L0 ybased on data from the MESSENGER spacecraft (the colour-coded foreground on
6 H( d, Z6 a8 K' `' P$ o+ @! k2 hcover, with a global surface mosaic in the background) to locate the oldest G U C6 t$ T& L5 _/ \9 F; ?
surfaces on Mercury and interpret the crater populations in the framework of a 6 ^1 N. h) F% F
recent lunar crater chronology. They conclude that the oldest surfaces were
4 t: [% G. p! ^# Bemplaced just after the start of the Late Heavy Bombardment 4.0 to 4.1 billion 8 c: o0 F7 V) S2 d8 G- B6 X
years ago. The large impact basins, not previously dated, yield a similar / e( U, N6 ~6 U
surface age. This agreement implies that resurfacing was global and due to 4 C0 [6 G7 D5 @- d* X u
volcanism, perhaps aided by heavy bombardment as previously suggested. Cover:
% V% A* N3 T$ D' F5 x8 ?' XSimone Marchi/MESSENGER data: NASA/JHUAPL/Carnegie Institution of Washington% y& N/ `5 p1 ?
5 q% z, t8 K* T' {" V9 x
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发表于 2013-7-5 23:43
发表于 2013-7-6 08:19
