Europe’s SMART-1 is the first of several lunar crashes on the drawing board.

Slight tweaks to SMART-1's orbit over the course of the summer allowed engineers to direct its impact point. (European Space Agency)
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Seems everyone wants a shot at the moon these days.

The European Space Agency’s SMART-1 spacecraft, which has been testing advanced technologies in lunar orbit since November 2004, will be sent crashing into a rocky plain known as the Lake of Excellence early Sunday morning (impact is set for 1:42 a.m. Eastern Time, although the exact timing depends on the uncertain lunar topography – SMART-1 may clip a mountain peak on an earlier pass). Telescopes on Earth will be watching, and scientists hope to learn something from the way lunar rocks and dust are thrown up by the impact, much as they did when NASA’s Deep Impact probe slammed into a comet nucleus last year.

This isn’t the first time such an experiment has been tried, nor will it be the last.

In 1999, NASA’s Lunar Prospector made a kamikaze dive into a shadowed crater near the moon’s south pole, hoping to melt and splash up whatever ice might exist there. It was a long shot, not part of the original mission plan, and astronomers weren’t surprised when they saw nothing.

In 2009, they’ll have another try with the Lunar Reconnaissance Orbiter, which is expected to map the lunar surface in unprecedented detail. Normally, the 4,400-pound upper stage rocket that boosts the orbiter to the moon would be thrown away after its fuel is spent. Instead, it will be sent crashing into the moon at 5,600 miles per hour. A second, smaller "shepherding spacecraft" equipped with cameras and other sensors will direct the impact, then observe from nearby, looking for water ice and vapor. Because the upper stage will hit the moon with 200 times the energy of the 1999 Lunar Prospector, scientists are more hopeful that this time, they may solve the nagging mystery of whether water exists at the lunar south pole. Why does it matter? Because future moon explorers could drink it or turn it into rocket fuel.

With NASA planning to send people to live on the moon for long stretches beginning in the 2020s, the agency would like a better handle on the danger from meteoroid bombardment. Every day, more than a ton of material rains down on the moon, and with no air to slow it down, even a pebble could do a lot of damage at a moonbase. Researchers at NASA’s Marshall Space Flight Center in Alabama are studying old data from seismometers left on the lunar surface during the Apollo era to see if they can detect meteorite hits (see a video of a recent impact here).

A group of students at Brown University in Providence, Rhode Island, has another idea. Their proposed First Lunar Appulsion Spacecraft at Hypervelocity (FLASH) concept would send a small, cheap spacecraft – little more than a guided rocket engine – smashing into the moon at 22,000 mph. Telescopes would watch the flash, as usual. The idea is to help scientists calibrate the flashes from natural meteoroids, since the size, mass, and chemical makeup of the artificial impactor would be known in advance.

Unlike SMART-1 and LCROSS, there’s currently no funding for FLASH. But the Brown students hope the mission’s low price tag—just $7.5 million—might move it from the drawing board to the launch pad.

Meanwhile, we can all enjoy the show from SMART-1 (the flash may be visible with a small telescope), and be thankful we don’t live in the Lake of Excellence -- however cool that address may sound.

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