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- 积分
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- 威望
- 17983
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- 26159
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The most heavily cratered terrains on Mercury exhibit $ J6 z2 c& b: V- ]8 t/ F2 k
a lower density of craters smaller than about 100 km in diameter than on the
& B8 e8 d$ p i1 t& gMoon, a deficit that has been attributed to resurfacing by formation of ancient " g1 [' {3 n& U6 ` Q
intercrater plains. Simone Marchi et al. used a crater areal density map : O* x" E5 f. H1 U% H; h
based on data from the MESSENGER spacecraft (the colour-coded foreground on 5 _, O# a8 z# u, w( d' L+ D
cover, with a global surface mosaic in the background) to locate the oldest : E2 z+ l& w: i& _. S% j1 ?
surfaces on Mercury and interpret the crater populations in the framework of a - Q' `4 f# s2 R: S
recent lunar crater chronology. They conclude that the oldest surfaces were
/ J3 W+ F' I' J) V4 J0 t1 o8 femplaced just after the start of the Late Heavy Bombardment 4.0 to 4.1 billion
v: N( q! e) V1 {years ago. The large impact basins, not previously dated, yield a similar
6 q$ I% w/ [8 @1 R& @. Y% E1 t& ?3 Bsurface age. This agreement implies that resurfacing was global and due to
1 s5 L) G! K. g* S* g$ }8 Q( M: Jvolcanism, perhaps aided by heavy bombardment as previously suggested. Cover:
+ i! y! m3 [8 u) q) O# L. j. W7 dSimone 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
