ICE: On The Moon

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ICE On The Moon

• Lindsay Johannessen
• PTYS 395
• All photos courtesy of
• Vasavada 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 10? 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 Moons 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 have
• been pixilated in
• white (north pole
• at top, south at
• bottom.

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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.