Mercury (and the Moon) possesses a tenuous atmosphere
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Transcript of Mercury (and the Moon) possesses a tenuous atmosphere
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PYTS 395B – Detecting Ice on the Moon 1
Mercury (and the Moon) possesses a tenuous atmosphere
Calcium now also seen at Mercury
Sodium emission at the Moon and Mercury shows temporal changes
Stirring of regolith by small impacts
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PYTS 395B – Detecting Ice on the Moon 2
Evidence for ice in polar craters of Mercury Evidence for ice at lunar poles
Clementine bi-static radar Lunar prospector neutron
Evidence for ice at poles of Mercury VLA radar returns
Sungrazing comets Kreutz group Source of water?
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PYTS 395B – Detecting Ice on the Moon 3
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PYTS 395B – Detecting Ice on the Moon 4
Feldman et al., 1998
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PYTS 395B – Detecting Ice on the Moon 5
Bussey et al., 1999
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PYTS 395B – Detecting Ice on the Moon 6
Margot et al., 1999
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PYTS 395B – Detecting Ice on the Moon 7
Modeling (Vasavada et al. 1999) shows temperatures in permanently shadowed craters are very low
These cold traps are favored condensation sites
Vasavada et al., 1999
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PYTS 395B – Detecting Ice on the Moon 8
Water leaves cold traps by sublimation 5-15% returns on Mercury 20-50% returns on the Moon The rest is lost
Water can be delivered by meteors and comets For Mercury these rates have been estimated Balance exists if Tice is ~113K
Killen et al., 1997
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PYTS 395B – Detecting Ice on the Moon 9
Lunar cold traps dry compared to Mercury Recent comet impact?
Polar inconsistency? More H in lunar north pole More permanent shadows in lunar south pole Burial depth differences Dispersed grains?