From the November 2013 issue

More missions that looked for Moon water

Learn more about the spacecraft that have tried to find out how icy our satellite is.
By | Published: November 25, 2013 | Last updated on May 18, 2023
For years, scientists have been on a quest to determine whether the Moon has a reservoir of water ice locked in its permanently shadowed polar craters.
The history of humans’ direct interaction with the Moon goes back to 1959, when the Soviets sent a probe from their Luna spacecraft crashing into the lunar surface and, shortly after, NASA’s Pioneer 4 made a close pass and returned data about the Moon’s radiation. Since then, astronauts have walked on the surface, people have lived in Earth orbit for months, and probes are continuing past the farthest reaches of the solar system. At this point in our space exploration, we have sent many orbiters to explore and impact the Moon, and multiple have detected its water.

Clementine, a joint NASA and military project, was not even meant to search for water. The radar experiment that bounced radio waves from shadowed craters to receivers back on Earth was an idea dreamed up after the craft was well into its mission. As far as last-minute decisions go, it worked out pretty well.

NASA launched the Lunar Prospector just four years after Clementine, in 1998. But this time, they looked for ice on purpose. And, surprise, they found it again!

Japan’s Selenological and Engineering Explorer (Kaguya) definitely saw hydrogen on the Moon. But was it in the wells of craters or not? Later results from the missions after this contextualized the data … kind of.

The main mission of NASA’s Lunar CRater and Observation Sensing Satellite (LCROSS) was to look for water, while it was merely a part of what the other crafts’ goals were. Let’s hear it for LCROSS’s single-minded dedication!

NASA’s Lunar Reconnaissance Orbiter (LRO) is the most sophisticated Moon-mapper yet, able to link hydrogen to its actual location on the Moon’s surface. Showoff!