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- 积分
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- 威望
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- 26159
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9 q# O5 i. u1 S, nThe most heavily cratered terrains on Mercury exhibit
3 l+ c5 e+ h8 ^6 D2 N$ Ea lower density of craters smaller than about 100 km in diameter than on the
L }5 G0 C: H$ d! sMoon, a deficit that has been attributed to resurfacing by formation of ancient * R6 M: M3 q" _; E/ Z
intercrater plains. Simone Marchi et al. used a crater areal density map
- y+ o D* F+ T5 U8 q4 \* Sbased on data from the MESSENGER spacecraft (the colour-coded foreground on * s; c- i5 U6 p
cover, with a global surface mosaic in the background) to locate the oldest
. s' [) `# q& `+ ~2 f msurfaces on Mercury and interpret the crater populations in the framework of a
/ r2 F3 m6 _5 G yrecent lunar crater chronology. They conclude that the oldest surfaces were
9 `7 s! L3 \: ^# cemplaced just after the start of the Late Heavy Bombardment 4.0 to 4.1 billion 8 m! d+ z y" z
years ago. The large impact basins, not previously dated, yield a similar
7 S2 l" f+ z- g" B" h& Xsurface age. This agreement implies that resurfacing was global and due to ) }4 a/ e5 a: r
volcanism, perhaps aided by heavy bombardment as previously suggested. Cover:
& J8 r6 N$ Y+ t" C' g* ~& ~Simone Marchi/MESSENGER data: NASA/JHUAPL/Carnegie Institution of Washington# D4 e- _; W# L. i9 z9 K
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发表于 2013-7-5 23:43
