The mystery of how the moon got its surface water has just got deeper, following the failure of an attempt to replicate the mechanism that was thought to produce it. Many planetary scientists assumed the water was created when particles from the solar wind hit lunar soils, but this idea has now been thrown into doubt.
“The solar wind cannot produce water in sufficient quantities to account for the results of the three missions that observed it,” says Raúl Baragiola, a member of the team at University of Virginia, Charlottesville, that tried to reproduce this effect in the lab.
For years, theorists have believed that protons from the solar wind could produce water on the moon by prying oxygen atoms away from minerals in the lunar soil and combining with them to form hydroxyl radicals (OH) or water (H2O). This hypothesis gained credibility recently with the observations of hydroxyl and water by NASA Deep Impact and Cassini missions, and the Indian probe Chandrayaan-1.
Baragiola and colleagues tested the idea by blasting protons at crystals of ilmenite and anorthite, two of the most common lunar minerals, in a high vacuum. They found no sign that water or hydroxyl radicals were produced. In fact, they found the opposite: the protons destroyed any traces of water that had remained in the minerals after 24 hours of baking prior to the experiment.
Carle Pieters of Brown University in Providence, Rhode Island, who was lead author of last year’s report from Chandrayaan-1, admits to being puzzled by the results, but the established hypothesis might yet be correct. Baragiola is planning to repeat his experiments with real lunar soil.
Journal reference: Icarus, DOI: 10.1016/j.icarus.2010.11.007
Read the full story at NewScientist.com.
Posted by: Soderman/NLSI Staff