A space rock collided with the Moon at a speed of 61,000 kilometres an hour during the total lunar eclipse in January this year, excavating a crater 10 to 15 metres across, scientists say.
Observers watching the total eclipse of the Moon on January 21 this year, witnessed a short-lived flash as a meteorite hit the lunar surface.
Researchers from the University of Huelva and Institute of Astrophysics of Andalusia in Spain used eight telescopes to monitor the lunar surface during the event.
The impact flash lasted 0.28 seconds and is the first ever filmed during a lunar eclipse, despite a number of earlier attempts.
Total lunar eclipses take place when the Moon moves completely into the shadow of the Earth. The Moon takes on a red colour -- the result of scattered sunlight refracted through the Earth's atmosphere -- but is much darker than normal.
The most recent lunar eclipse took place on January 21 this year, with observers in North and South America and Western Europe enjoying the best view.
Just after the total phase of the eclipse began, a flash was seen on the lunar surface. Widespread reports from amateur astronomers indicated the flash -- attributed to a meteorite impact -- was bright enough to be seen with the naked eye.
"Something inside of me told me that this time would be the time," said Jose Maria Madiedo of the University of Huelva.
Unlike the Earth, the Moon has no atmosphere to protect it and so even small rocks can hit its surface.
Since these impacts take place at huge speeds, the rocks are instantaneously vapourised at the impact site, producing an expanding plume of debris whose glow can be detected from our planet as short-duration flashes.
Researchers found that the incoming rock had a mass of 45 kilogrammes, measured 30 to 60 centimetres across, and hit the surface at 61,000 kilometres an hour.
The impact site is close to the crater Lagrange H, near the west-south-west portion of the lunar limb.
The impact energy is estimated to have been an equivalent to 1.5 tonnes of TNT, enough to create a crater up to 15 metres across, or about the size of two double-decker buses side by side.
The debris ejected is estimated to have reached a peak temperature of 5,400 degrees Celsius, roughly the same as the surface of the Sun.
"It would be impossible to reproduce these high-speed collisions in a lab on Earth. Observing flashes is a great way to test our ideas on exactly what happens when a meteorite collides with the Moon," Madiedo said.