Just a few decades ago, Earth's Moon was on the receiving end of an asteroid-sized body that slammed into the lunar surface.
But finding telltale evidence from the celestial smacking proved elusive. The crater would be well below the resolution limit of Earth-based telescopes.
A research team now believes they've spotted the lunar leftovers from the impact, caught in images taken by a robotic lunar orbiter.
Eagle-eye scientists
In 1956, an amateur astronomer -- Leon H. Stuart -- reported in the Strolling Astronomer, that he had observed and photographed a flash a few years earlier on the Moon. This event is the only unambiguous record of the crash of an asteroid-sized body onto the lunar surface.
Now, decades later, a study of lunar images snapped by the Clementine spacecraft as it orbited the Moon in 1994 has uncovered a candidate crater formed by the impact.
Eagle-eye scientists, Bonnie Buratti of NASA's Jet Propulsion Laboratory and Lane Johnson of Pomona College in Claremont, California have locating a near mile across (1.5-kilometer) feature with a fresh-appearing ejecta blanket at the location of the flash. Spectral analysis of the crater, they report, reveals it to be bluer and fresher than other young craters.
Striking image
"We identified the crater on processed multispectral Clementine images. With the correct processing procedure and analysis it is obvious," Buratti told SPACE.com. The crater and resulting eject blanket of material tossed up by the impact is small. So tiny, in fact, it's not visible from Earth or on images taken by the Lunar Orbiter probes dispatched to the Moon in preparation for the Apollo lunar landing expeditions, she added.
A full account of their research has been accepted for publication in a forthcoming issue of Icarus, the prestigious professional space science journal.
Buratti and Johnson estimate that the energy of the impact event was about 0.5 megatons, resulting in the newly found feature. The radius of the impacting body was over 65-feet (20 meters). Such an event occurs every 10-50 years, they report.
Another result of their work suggests that the effects of space weathering -- intense solar radiation and meteorites striking the surface -- takes place very rapidly on the Moon, Buratti said.
The team's lunar detective work was performed in part at the Jet Propulsion Laboratory/California Institute of Technology under contract to NASA, and funded in part from a National Science Foundation grant.
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