ICE: On The Moon
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Transcript of ICE: On The Moon
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ICE: On The Moon
Lindsay JohannessenPTYS 395
All photos courtesy ofVasavada el at., Feldman et al., Margot et al.,
www.nasa.gov, www.psrd.hawaii.edu, http://apollo.sese.asu.edu
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Ice: How would water ice get to the Moon?
- Impactors: Comets, Meteors ect…These would have a great amount (or release a great amount) of water ice onto the Moon.
- Solar Wind Sputtering: creating water ice in the exopshere.
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What happens to this water ice when its deposited there?
- They bounce around for a while until one of the following happens:
- Bounce around the exopshere in ballistic trajectories for however long they can
survive (being destroyed in a number of ways like photodissociation, solar-induced desorption etc…)
- Eventually land in a safe, permanently shaded area of the North or South pole regions of the Moon.
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- Studies show that approximately 20 – 50% of accumulated water deposits on the Moon should be settled as ice.
- Here, we see the evaporation rate as a function of temperature
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Where can this water ice form?
- Subsurface ice is referenced to be stable within 2° of latitude from the poles, meter-thick ice will be located no further than 13° from the poles (Vasavada et al.)
- Only in constantly shadowed areas will this water ice have a chance to accumulate (crater floors and walls, crescent shadow regions).
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Shadowing on the Moon
- In this image, we see how the effective shadow on the left side could potentially house water ice in the crater walls and shadowed floor. (Image not of polar region)
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If there is ice, how much could be there?
- Approximately 1850 km² around each polar region. (3700 km² in entirety)
- Possible depth of up to 2 meters in certain accumulations.
- All in all, each region could contain up to 3 X 10⁹ metric tons of water ice.
- Possible depths reach to that under a regolith layer of up to 40 cm.
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What are the theories? (How did we find out?)
- First, we see what areas are permanently shaded on the Moon.
- Analyze data taken from the LP spacecraft measuring hydrogen detection from a neutron spectrometer in polar regions.
- Compare data collected from other known icy bodies, such as Comets and meteors.
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Survival…
- If there is water ice on the moon, under what circumstances would it need to ‘survive’?- Constant shadowing from solar radiation- Protection by a regolith layer
- It is necessary to have a good understanding of the topography of the Moon’s poles.- Scientists use a dual radar inferometer to measure slopes of lunar topography.
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Discrepancies: - Different researchers predict different
latitudes for stable water ice at the poles:- Vasavada et al. say no more than 2°.- Nozette et al. say up to 2.5°, in agreement with Margot et al. and Feldman et al.
- Shadowed regions versus hydrogen data? - South pole regions have more constantly shadowed regions than the north.- However, north pole regions have more hydrogen data.
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- This implies that the hydrogen in the north polar regions may not be associated with any kind of water ice.
South Pole regions North Pole regions
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More discrepancies…
- Can we really detect further than one meter through regolith?
- Are there Layers?
Cold traps havebeen pixilated inwhite (north poleat top, south atbottom.
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Current Studies:
- LCROSS (Lunar Crater Observation and Sensing Satellite) will be launched this October.
It will send out a probe into one of the possible icy areas of the Moon and a flyby secondary craft will gather data from the impact.