Geoscience Reference
In-Depth Information
Assuming that cometary ice exists at both the Moon and Mercury, it is
still puzzling that a thick deposit appears close to the surface on Mercury,
where it would be buried very quickly. Are we simply observing a spe-
cial time, soon after a recent comet impact on Mercury? Recent observa-
tions of Sungrazing comets by the Solar Heliospheric Observatory suggest
that there is currently a large population of comets (Kreutz family) that
cross Mercury's orbit. 23 A similar population could have existed in the
past to supply the putative deposits at Mercury. Further, it is true that the
impactor flux is greater at Mercury; but not by enough to account for
the difference in lunar and hermean near-surface ice.
Perhaps the loss rate from exposure is greater than our model has
incorporated. Then the slow burial of ice on the Moon would result in
a lower retention fraction. That would account for the observed differences
at Mercury and the Moon. Remote sensing data from upcoming lunar and
hermean missions will provide data that can help determine the contents of
the PSRs. They will give more information and may help better constrain
the possible source and retention mechanisms.
Acknowledgments
This
work
was
supported
by
NASA
grants
NNG05GB84G
and
NNG05GA80G.
References
1. A. R. Vasavada, D. A. Paige and S. E. Wood, Icarus 141 (1999) 179.
2. K. Watson, B. C. Murray and H. Brown, J. Geophys. Res. 66 (1961) 3033.
3. W. C. Feldman et al. , Science 241 (1998) 1496.
4. J. K. Harmon and M. A. Slade, Science 258 (1992) 640.
5. A. L. Sprague, D. M. Hunten and K. Lodders, Icarus 118 (1995) 211.
6. L. Starukhina, J. Geophys. Res. 106 (2001) 14701.
7. R. R. Hodges, J. Geophys. Res. 107 (2002) 5125.
8. J. Arnold, J. Geophys. Res. 84 (1979) 5659.
9. B. J. Butler, J. Geophys. Res. 102 (1997) 19283.
10. M. J. Cintala, J. Geophys. Res. 97 (1992) 947.
11. G. Neukum et al. , Planet. Space Sci.
(2001) 1507.
12. D. H. Crider and R. R. Vondrak, J. Geophys. Res.
49
108
(2003) 5079.
13. D. H. Crider and R. R. Vondrak, Adv. Space Res.
31
(2003) 2293.
32
14. D. H. Crider and R. M. Killen, Geophys. Res. Lett.
(2005) L12201.
15. J. K. Harmon, P. J. Perillat and M. A. Slade, Icarus
149
(2001) 1.
Search WWH ::




Custom Search