The space rock that hit the moon at 61,000 kilometers at the hour

Observers who witnessed the total eclipse of the January moon witnessed a rare event: a brief flash when a meteorite hit the lunar surface. Spanish astronomers now think that the space rock collided with the Moon at 61,000 kilometers at the hour, digging a crater 10 to 15 meters wide. Professor Jose Maria Madiedo of the University of Huelva and Dr. Jose L. Ortiz of the Institute of Astrophysics of Andalusia publish their results in a new Monthly Notices from the Royal Astronomical Society.

Lunar total eclipses occur when the Moon moves completely into the shadow of the Earth. The moon takes on a red color – the result of scattered sunlight refracted in the Earth's atmosphere – but is much darker than normal. These spectacular events are regularly observed by astronomers and the general public.

The last lunar eclipse took place on January 21, 2019, with observers from North and South America and Western Europe enjoying the best view. At 4141 GMT, just after the start of the total phase of the eclipse, a flash was seen on the lunar surface. Many reports from amateur astronomers have indicated that the flash, attributed to a meteorite impact, was bright enough to be seen with the naked eye.

Madiedo and Ortiz use the Moon Impact Detection and Analysis System (MIDAS) with the help of eight telescopes located in southern Spain to monitor the lunar surface. MIDAS video footage recorded the moment of impact.

The impact flash lasted 0.28 seconds. It is the first film ever made during a lunar eclipse, despite several previous attempts.

"Something inside me said it would be the moment," Madiedo said, impressed by the event's observation because it was brighter than most events regularly detected by the survey.

Unlike the Earth, the moon does not have an atmosphere to protect it and even small rocks can hit its surface. Since these impacts occur at tremendous speeds, the rocks are instantly vaporized at the impact site, producing an expanding debris plume that can be detected from our planet in the form of short-duration lighting.

The MIDAS telescopes observed the impact of the flash at several wavelengths (different light colors), thus improving the analysis of the event. Madiedo and Ortiz conclude that the incoming rock had a mass of 45 kg, measured 30 to 60 centimeters in diameter and reached the surface at 61 000 kilometers at the time. The impact site is near the Lagrange H crater, near the west-southwest corner of the lunar limb.

The two scientists estimate that the impact energy is equivalent to 1.5 tons of TNT, which is enough to create a crater with a maximum width of 15 meters, about the size of two double-decker buses side by side. . It is estimated that the ejected debris reached a maximum temperature of 5400 degrees Celsius, about the same as that of the sun's surface.

Madiedo commented, "It would be impossible to replicate these high-speed collisions in a lab on Earth." Flash observation is a great way to test our ideas about what exactly is happening when a meteorite goes into collision with the moon. "

The team plans to continue monitoring the impacts of meteorites on the lunar surface, particularly to understand the risk they pose to astronauts, who are expected to return to the moon in the next decade.