In what experts are calling “totally sweet”, NASA has announced plans to crash a 2000 kg impactor into the moon, triggering a 28m-diameter crater and a six-mile high plume of debris which will be visible from Earth via telescope. No, this isn’t April 1st; the four-month mission commences next Thursday, with intended impact on October 8. The purpose of the mission is to settle the question of whether there is in fact frozen water in the craters of the moon’s south pole.
Water ice in the ejected dust cloud will sublime (convert from a solid to a gaseous state) under the influence of solar irradiation. The rate of this sublimation depends primarily on the water to ice ratio and particle size, with ~0.1 mm dust rich (1% water ice) particles subliming their water in several minutes. The surface brightness of the cloud increases as the ejecta expands; in 40 seconds, the ejecta cloud will fill a 1 arc second observing aperture as seen from Earth-based telescopes. Subsequently, the water molecules will be dissociated by solar UV radiation and the OH molecule will be observable in emission at 308nm.
What I find interesting about this is how NASA can do something like this without consulting the international community. Sending rovers or astronauts to make observations is one thing, but creating giant explosions seems rather unilateral. Granted, an explosion of this size will cause no lasting changes, except for adding one more crater to the already pockmarked Luna, and the potential gain to the space program if water is indeed found would be huge, but it is interesting that there are no laws to govern this sort of thing. There was an attempt at a Moon Treaty in 1979, but since no major space-power signed the agreement, it is considered a failure. I imagine it is only a matter of time before we start to experience tensions over jurisdictions in regards to celestial bodies, especially with China and India‘s rapidly expanding space programs.