By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - A meteorite as large as 4-1/2 feet in diameter smashed into the moon in September, producing the brightest flash of light ever seen from Earth, astronomers said this week.
Similarly sized objects pummel Earth daily, though most are destroyed as they plunge through the planet's atmosphere. NASA says about 100 tons of material from space enter Earth's atmosphere every day.
The moon, with no protective atmosphere, is fair game for celestial pot-shots. The evidence is all over its cratered face and is occasionally recorded by cameras on Earth.
Such was the case on September 11, 2013, when a pair of telescopes in Spain, which were automatically trolling for lunar meteorite impacts, hit pay-dirt with the longest, brightest flash ever observed on the moon.
"At that moment I realized that I had seen a very rare and extraordinary event," astronomer Jose Madiedo, with the University of Huelva in Spain, said in a statement.
Typically, flashes of light from meteorite impacts on the moon last just a fraction of a second. The September flash was nearly as bright as Polaris, the North Star, and the afterglow lasted another eight seconds, a video recording made by Madiedo shows.
"Anyone on Earth who was lucky enough to be looking at the moon at that moment would have been able to see it," the United Kingdom's Royal Astronomical Society said in a press release.
Scientists estimate the meteorite was between 2 feet and 4.6 feet in diameter and weighed about 882 pounds (400 kg.)
Moving faster than 37,900 mph, the meteorite smashed into a region known as Mare Nubium with the force of about 15 tons of TNT. It likely left behind a 130-foot (40-meter) wide crater.
Based on their ongoing observations, Madiedo and colleagues estimate that objects roughly 3.3 feet (1 meter) hit Earth's atmosphere about 10 times more often than previously thought. Occasionally, some create bright so-called "fireball" meteors in the night-time skies.
The Spanish telescopes are part of the Moon Impacts Detection and Analysis System, which monitors the lunar surface.
The research was published on Sunday in the Monthly Notices of the Royal Astronomical Society.
(Reporting by Irene Klotz; Editing by Dan Grebler)