A decade-long lunar mystery has finally been solved. Satellite imagery of the surface of the moon has revealed the final resting place of the European Space Agency’s first lunar orbiter, SMART-1, including the gouge it made as it tumbled across the surface and the spray of material when it finally came to a stop.
Launched in 2003, SMART-1 was in effect a bit of a guinea pig satellite, being the first such device to leave the orbit of Earth and glide to the moon using nothing but solar power. After its 13-month trip, it collected 3D images of the moon’s pockmarked surface and readings of the chemical elements in the lunar rocks, before being deliberately crashed in 2006. Since then, little has been known about its fate.
As Bernard Foing, the then project scientist for SMART-1, explains: “SMART-1 had a hard, grazing and bouncing landing at two kilometres [1.2 miles] per second on the surface of the moon.” But even though the impact was caught on camera by the Canada-France-Hawaii Telecope (CFHT), there were no other spacecraft orbiting the moon to give a detailed view of it.
“Finding the precise location became a 'cold case' for more than 10 years,” continues Foing. “For this 'Crash Scene Investigation', we used all possible Earth witnesses, observational facts and computer models to identify the exact site and have finally found the scars.”
By using high-resolution images taken from NASA’s Lunar Reconnaissance Orbiter, they were able to identify the markings and scratches on the moon consistent with the medium-sized satellite tumbling across the surface. The pictures show a straight gouge roughly 4 meters (13 feet) wide and 20 meters (66 feet) long intersecting a small crater.
At the end of this groove, they are even able to see a fan of white ejecta about 7 meters (23 feet) across. This matches with the expected impact of the object, as it skidded across the moon before bouncing slightly, and finally coming to rest. The sprays of ejecta are thought to be about 40 meters (130 feet) in length.
The impact spot is incredibly close to where the small flash of impact was imaged over a decade ago, and consistent with those calculated when it was planned, but now the case has finally been put to rest with the photographic evidence.
“The next steps will be to send a robotic investigator to examine the remains of the SMART-1 spacecraft body and 'wings' of the solar arrays,” says Foing, although to date ESA do not actually have any plans to send a rover to the moon, so we may have to wait a while.