Moon and Spica

As missions to the Moon go, Clementine was small, cheap, and low-key. Yet its accomplishments were big and long-lasting. Its maps of the lunar surface are still some of the best around. And scientists have worked long and hard to expand on its discovery of frozen water at the Moon’s poles.

Clementine was launched 25 years ago today. It was designed by the Defense Department to test sensors, batteries, and other technologies. It was targeted for the Moon, with a follow-up trip to an asteroid.

Clementine arrived at the Moon a few weeks later. During more than two months in orbit, it took almost a million pictures of the lunar surface, in multiple wavelengths. Those images produced the first map of the entire lunar surface. And they revealed the composition of the surface.

The probe also measured the elevation of the surface. And by tracking its radio waves, scientists measured the Moon’s “lumpy” gravity. Clementine also bounced radio waves off the poles. A radio telescope on Earth measured the reflected waves, which revealed ice hidden inside craters.

Clementine left lunar orbit in May of 1994 and headed for an asteroid. But a faulty thruster drained away its fuel, bringing its mission to an end.

And its first target has a bright companion the next couple of nights. The star Spica is to the lower right of the Moon as they climb into view after midnight tonight, and closer to the upper right of the Moon tomorrow night.

Script by Damond Benningfield