NASA is reporting that a meteor smashed into the Moon on March 17, 2013 at a speed of 56,000 mph, sparking the biggest and brightest explosion ever observed and creating a crater 65 feet wide (20 meters).
The explosion was so bright that anyone looking at the Moon at the time might have seen it.
A NASA moon monitoring telescope captured the blast created by a space rock about the size of a small boulder believed to be part of a meteor swarm in the region of the Earth-Moon system..
Officials at the Meteoroid Environment office say they have recorded more than 300 lunar impacts since they began monitoring the lunar surface for impacts eight years ago. They say the latest impact was the biggest and brightest ever seen in eight years of monitoring the surface of the Moon. It was many orders of magnitude brighter than any previous impacts observed.
NASA said in a release: "Anyone looking at the moon at the moment of impact could have seen the explosion — no telescope required. For about one second, the impact site was glowing like a 4th magnitude star."
NASA reports that Bill Cook of NASA's Meteoroid Environment Office said in a statement: "On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium. It exploded in a flash nearly 10 times as bright as anything we've ever seen before."
According to National Geographic, Robert Suggs, manager of NASA's Lunar Impact Monitoring Program at Marshall Spaceflight Center in Huntsville, Alabama, said: "We have seen a couple of others in the ‘wow’ category but not this bright."
According to NASA, astronomers have been monitoring the Moon for lunar meteor impacts for the past eight years, and have not seen an impact as powerful as that.
They detected the impact long after it had occurred when Suggs was reviewing a video recorded by one of the Moon monitoring program's 14-inch telescopes. He said: "It jumped right out at me, it was so bright."
Frame from NASA telescope video capturing lunar flash on March 17, 2013. Credit: NASA/Robert Suggs
NASA scientists estimate the impacting rock at roughly about a foot wide (0.3 to 0.4 meters) and weighing about 88 lbs (40 kg). It generated an explosion equivalent to about 5 tons of TNT. NASA officials say the blast lasted a second and shone like a 4th magnitude star. It could be seen with unaided eyes.
False-color frames from the original black and white video show the explosion in progress. At its peak, the flash was as bright as a 4th magnitude star
The discovery led scientists to go through their records for evidence of other impacts. They found that more space rocks were hitting the Moon than previously thought. They also found that the impact could have been part of a meteoroid stream passing through the region of the Earth-Moon system. According to Cooke: "On the night of March 17, NASA and University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth. These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt."
The Earth is spared more impacts because its surface is protected a blanket of gases that make up the atmosphere. However, the Moon has no atmosphere so its surface is exposed to more direct hits. According to NASA, its monitoring program has detected more than 300 meteor impacts since 2005. More than half of the impacts come from known meteoroid streams such as the Perseids and Leonids.
NASA also explains that we are able to detect the flash of lunar impacts in spite of the fact that there is no oxygen on the Moon to support combustion because: "Lunar meteors don’t require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site."
NASA scientists hope to confirm the observation with close-up photography from the Lunar Reconnaissance Orbiter, Suggs said: "They are planning to image that location in hopes of finding the crater which would be very significant scientifically."
NASA explains that part of the reason why scientists are interested in monitoring lunar impacts is because when astronauts are sent to the Moon they will need to have an idea of the risk of a lunar impact at the area of the Moon's surface where they plan to make landing. Cooke said: "We'll be keeping an eye out for signs of a repeat performance next year when the Earth-Moon system passes through the same region of space. Meanwhile, our analysis of the March 17th event continues."