Tuesday, August 22, 2006

Watching Lunar Dust Settle

Understanding the effects of meteorites and space "junk" is important for our colonization of the moon and Mars.

By David Chandler

A 3-D model of the SMART-1 spacecraft, slated to crash into the moon on September 3. (Credit: European Space Agency)

When the SMART-1 (Small Missions for Advanced Research in Technology) spacecraft smashes into the lunar surface on September 3, it will provide some valuable information about the moon -- and the frequent impacts that take place there.

The European Space Agency (ESA), which built SMART-1, is still enlisting observers to capture images and data during the brief moment when the craft completes its spiraling descent and crashes into the Lake of Excellence (Lacus Excellentiae), a volcanic plain in the moon's southern mid-latitudes.

Even binoculars might be adequate for detecting the flash of light when the 366-kilogram craft hits the surface at about two kilometers per second. More importantly, though, bigger telescopes with high-speed video or spectroscopic detectors could provide important data about the lunar surface and the dynamics of such impacts in a vacuum.

"We look for fast imaging of the impact and of the associated ejected material, and for spectroscopic analysis -- for example, to find hints about the mineralogy of the impact area," says Bernard Foing, ESA's project scientist for SMART-1.

Like the Deep Impact mission that smashed into comet Tempel 1 last year, this mission could lead to an improved understanding of the composition of this unexplored region of the moon, and of the strength and material properties of the surface -- information that could be useful as NASA prepares for a new generation of human landings on Mars, slated to begin in 2018.

Future "moon-crash" missions could reveal even more. For example, a mission called LCROSS (Lunar Crater Observation and Sensing Satellite) is planned to hit the moon's polar region in 2009, where some data suggest there may be significant amounts of water-ice in the soil. Analysis of the plume of material ejected by that mission might not only prove the presence of that ice, but also reveal how much there is, and thus whether or not it could be a practical source of drinking water and even rocket fuel for future lunar missions.

Another proposed mission, designed by students at Brown University, could help to answer some fundamental questions about the natural meteorite impacts that occur all the time on the moon as well as on the Earth and other planets.

The mission, dubbed FLASH (First Lunar Appulsion Spacecraft at Hypervelocity), would be the first ever to hit the moon at a speed comparable to natural meteorites, and thus it could provide a highly useful baseline for calibrating what size object it takes to produce a given brightness of the impact flash. That, in turn, would allow better estimates of the number of impacts that occur naturally on the airless moon -- something that could become an important safety issue for scientific research instruments on the moon, eventual human exploration, and ultimately permanent lunar bases.