Plantetary scientists who have analyzed the data from the MESSENGER probe's initial flyby of Mercury are "astonished." Mercury was always thought to be, essentially, a dead lump of rock: no water, no internal geological processes like vulcanism - heck, at one time we thought it didn't even rotate. Now we know it was shaped partly by volcanos and that its thin atmosphere, according to sample ions scooped up in MESSENGER's first visit, does indeed contain water vapor. A study of flyby data also confirmed a theory that Mercury has a liquid core.
MESSENGER science team member Thomas Zurbruchen said of the water: "Nobody expected that. I don't know a single person that did. We were astonished, just astonished."
How exactly does this sun-blasted planet boast water of any sort? There are three theories. The water may have come from comets; it may be the results of chemical reactions between the solar wind and the rocks of Mercury; or the planet may maintain (like Mars but on a much smaller scale) subsurface water ice in the polar regions.
COMMENT: This data (from the first flyby, remember: MESSENGER will be studying the planet for a long time yet) reminds us how much we have to learn. We are still learning basic information about a planet in our own solar system, information that contradicts the expectations of scientists who have studied the planet for many years. What else lies in the infinite realms beyond Earth, awaiting discovery?