A space rock smashed into the Moon and left a huge crater in its surface – and chose its timing exactly right, scientists have said.
During the total lunar eclipse in January, even amateur observers spotted a very short flash in the corner of the lunar surface.
Right away, scientists got to work trying to understand what had caused it and what it might tell us about our nearest neighbour. And now the researchers have revealed early results from that study, published in a new paper in the Monthly Notices of the Royal Astronomical Society.
The rock hit the moon while it was going 61,000 kilometres an hour, they said, and left a crater behind that will be 10 to 15 metres across. When it hit, it did so with the force of 1.5 tonnes of TNT, throwing out debris that was as hot as 5400 degrees Celsius, roughly the same as the surface of the Sun.
Despite all that force, it lasted only 0.28 seconds.
The Moon has no atmosphere to protect it from such impacts, meaning that even small rocks can make their way to the planet and hit its surface. They are often travelling at very fast speeds when they arrive, meaning the rocks vapourise instantly and leave a plume of debris that can be seen even from Earth.
That flash was the first ever to be filmed during a lunar eclipse, despite repeated attempts by scientists.
"Something inside of me told me that this time would be the time", said Madiedo, who was impressed when he observed the event, as it was brighter than most of the events regularly detected by the survey.
By analysing the flash using a vast set of telescopes, the researchers were able to conclude that the rock had a a mass of 45kg, measured 30 to 60 centimetres across, and hit the surface at 61,000 kilometres an hour.
The team plan to keep watching for such impacts in the future, and learning more about how they happen. As well as yielding important scientific information, such study will be necessary to ensure the safety of the astronauts who are expected to head back to the lunar surface in years to come.
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