Two years ago March 17 an object the size of a small boulder hit the surface of the moon in Mare Imbrium and exploded in a flash of light nearly 10 times as bright as anything ever recorded before. Mare Imbrium is a lunar “sea” that forms the left eye in the Man in the Moon face we see at full moon.
NASA video of the meteorite impact that created a new moon crater
The impact and explosion were recorded with a video camera at NASA’s Marshall Space Flight Center. Based on the brightness of the flash, scientists determined a space rock about a foot wide struck the lunar surface, big enough to hollow out a substantial crater. After pinpointing the impact’s coordinates, the information was relayed to NASA’s Lunar Reconnaissance Orbiter (LRO) team, which then directed the probe to take pictures of the area in hopes of finding a fresh impact scar.
Nothing was found at first because the low resolution video images didn’t allow for precision targeting. So the team broadened their search to adjacent swaths of terrain. After several attempts, they noticed something unusual – streaks that looked like faint rays. Could it be part of a classic blast pattern left by impact debris showering down on the moon’s surface?
They did the logical thing and traced the rays back to their convergence point. When the LRO was directed to photograph the new coordinates, immediately a fresh, new crater at the center of that pattern was revealed in photographs sent back to Earth.
The crater itself is small, measuring 61.7 feet (18.8 meters) in diameter, but its influence large; debris excavated by the sudden release of energy flew for hundreds of meters. More than 200 related changes, including surface material swept away and smaller secondary impacts, were spotted up to 19 miles (30 km) away. Before and after photos clearly show that less than a year prior, no crater was there.
Hundreds of changes have been recorded by the Lunar Reconnaissance Orbiter during its four years at the moon by comparing old and new images called “temporal pairs”. More than 25 new impacts have been discovered this way.
While we’re on the topic, the crescent moon will pass just 3° south or left of Venus this evening in the western sky at dusk. They should make for an attention-grabbing scene. Be sure to look up!