There's nothing like a good map to help plan a trip – to the moon.
This helps explain why scientists with the National Aeronautics and Space Administration this week unveiled the most detailed map yet of the lunar surface. The results are expected to play a key role in helping mission planners working on two lunar-science missions scheduled for launch later this year.
The new map covers a small patch of the surface, to be sure – some 644 kilometers by 402 kilometers (400 by 250 miles). But it includes the lunar south pole's Shackleton Crater, considered by many to be a prime target for a manned landing sometime after 2020. The crater's interior lies in perpetual shadow and may hold water ice in its depths.
"The south pole of the moon certainly would be a beautiful place to explore," says Doug Cooke, a top official with NASA's exploration systems mission directorate. Consider the view: A vast crater four times deeper than the Grand Canyon yawning before you, with summits on the horizon as tall as Mt. McKinley.
Until now, the best images of the surface derived from mapping missions have spotted objects as small as 1 kilometer across. This map picks up objects as small as 20 meters across – or about the size of a large yacht. Instead of an orbiter, scientists at the Jet Propulsion Laboratory (JPL) used radar and three giant antennas at the Goldstone tracking facility in California's Mojave Desert. For 90 minutes, the team bounced powerful signals off the surface at the moon's south pole. The results revealed a moonscape far rougher than previous maps showed.
The results come as NASA prepares to launch its Lunar Reconnaissance Orbiter and a mission called LCROSS. Both missions piggyback on the same rocket. While the orbiter takes up its repetitive swings around the moon, LCROSS will send its upper stage rocket and sensor package hurtling toward the bottom of Shackleton Crater in quick succession. The rocket will kick up an enormous plume of material. The sensor package will follow close on its heels to analyze the chemicals in the plume before it, too, smacks into the crater floor. Scientists say they expect to be able to watch the collision with earthbound telescopes.
For its part, the LRO will be making images of the lunar surface and gathering information on the moon's topography using a radar-like device that bounces a laser, rather than radio signals, off the surface.
Scott Hensley, a scientist at JPL who took part in the latest radar-mapping effort, notes that the orbiter's laser-like radar, or lidar, will be able to match Goldstone's 20-meter resolution at the south pole after some eight months of orbiting the moon. But the orbiter can't bring that level of detail to as wide a swath of the south pole as can the radar. But where the radar can distinguish changes in elevation of roughly five meters, the LRO will be able to detect changes in terrain height of around one meter.
But for other parts of the moon, the LRO will only match the one-kilometer resolution of past missions. The Goldstone radar still has the best chance of spotting those yacht-sized objects anywhere on the moon scientists can aim it, making it for now the lunar cartographer to beat.