Lunar Planetary Society Conference 2013:
Seeing in Permanent Shadow (on Mercury)
by Michael Poston
The case for water ice hidden in permanently shadowed regions at the north pole of the planet Mercury received another boost recently. On Wednesday March 20, 2013 at the Lunar and Planetary Science Conference, Nancy Chabot presented the very first visible-light images of what is in the shadows of these polar craters.
As Emily reported previously, radar return from Arecibo shows signals consistent with, but not unique to, large deposits of water ice inside the permanently shadowed regions at Mercury’s poles. Numerical models suggest temperatures plenty cold to maintain water ice for millions of years, exactly where the radar signals show potential ice. Measurements of neutron depletion are consistent with hydrogen-bearing molecules, such as water, at the poles, but cannot resolve their exact location in the same way as radar can.
The final piece of the pre-existing story is the strength of the reflection from the MESSENGER Laser Altimeter instrument, which measures the strongest reflection from its 1064 nm infrared laser in the coldest parts of permanent shadow…
(read more: Lunar Planetary Soc.)
(images: NASA / JHUAPL / CIW / NAIC, Arecibo Observatory)