Econintersect: Mercury (example of surface shown in picture) is the closest planet to the sun and has surface temperatures as high as 8000F (7000K, 4300C). That might seem like an unlikely environment to find water or ice. However, the axis declination and the planetary rotation are such that some surface regions near the poles receive little or no sunlight at any time. Surface temperature measurements of the Mercury night have found readings as low as 1oo0K (-1730C, -3400F), certainly cold enough to hold onto ice with limited sublimation. New data from the NASA MESSENGER spacecraft has now provided quite convincing data that water in significant amounts does exist on this "hot" planet.
According to Wikipedia, shiny areas found at the bottom of polar craters that would be permanently shielded from the very low angle polar sun have been thought to possibly be ice since the 1970s. New data from NASA appears to confirm this hypothesis. One of the papers published by NASA scientists in the latest Science has determined that the amount of ice at the poles of Mercury is between 2 × 1016 to 1018 g. That is between 20 billion and 2 trillion tons. The scientists say that this amount is consistent with what could have been delivered by "comets or volatile-rich asteroids." NASA terms the amount "abundant."
The composition of the water bearing material varies with depth. At the surface data measures hydrogen concentrations consistent with a material containing less than 25% water. But at depths only 10 to 20 cm (4-8 inches) the material is almost pure water. These ice reservoirs are quite shallow by earthly standards, estimated to be 10's of cm thick. If 100 cm thick (1 meter) the "frozen lake" would be a little over 3 feet deep.
But the latest data also raises some new questions. From the NASA website:
"But the new observations have also raised new questions," adds Solomon. "Do the dark materials in the polar deposits consist mostly of organic compounds? What kind of chemical reactions has that material experienced? Are there any regions on or within Mercury that might have both liquid water and organic compounds? Only with the continued exploration of Mercury can we hope to make progress on these new questions."
Below is an image of the water rich polar region from NASA. Click on the graphic for a larger image with caption:
See also Info Graphic of the Day 21 December 2012.
- Mercury (planet) (Wikipedia)
- Thermal Stability of Volatiles on Mercury (David A. Paige et al, Science)
- Evidence for Volatiles on Mercury's Poles (Gregory A. Neumann et al, Science)
- Neutron Spectrometer Reveals Water Ice on Mercury, (David J. Lawrence et al, Science)