Unlike the Earth, the Moon has no atmosphere to protect it and even small rocks can hit its surface.
Since these impacts take place at huge speeds, the rocks get instantaneously vaporised at the impact, producing an expanding plume of debris whose glow can be detected from our planet as short-duration flashes.
Observers watching the January 21 total eclipse saw a short-lived flash as a meteorite hit the lunar surface, according to a study published in the journal Monthly Notices of the Royal Astronomical Society.
Observers in North and South America and Western Europe enjoyed the best view of the lunar eclipse. Just after the beginning of the eclipse, a flash was seen on the lunar surface.
Amateur astronomers indicated that the flash was bright enough to be seen with the naked eye.
The Moon Impacts Detection and Analysis System (MIDAS), which uses eight telescopes in south of Spain to monitor the lunar surface, recorded the moment of impact. Spanish astronomers Jose Maria Madiedo of the University of Huelva and Jose L. Ortiz of the Institute of Astrophysics of Andalusia operate the MIDAS.
The impact flash lasted 0.28 seconds and is the first filmed during a lunar eclipse, despite a number of earlier attempts. MIDAS telescopes observed the impact flash at multiple wavelengths (different colours of light), improving the analysis of the event.
Madiedo and Ortiz concluded that the incoming 30-60 cm rock had a mass of 45kg and hit the surface at 61,000 km an hour.
“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.
The impact site is close to the crater Lagrange H, near the west-south-west portion of the lunar limb, the study said.