Scientists have determined the origin of the second moon that the Earth had in the fall – it’s definitely not space debris

From the end of September to the end of November 2024, the Earth had a “second Moon” – a ten-meter asteroid lingered not far from the planet. Astronomers have been monitoring it since August, immediately after its discovery by the Planetary Defense Service. There was a possibility that these were just the remains of a rocket from one of the previous missions. A group of astronomers conducted a series of observations and defended the “small Moon”, proving that this object cannot be space debris.

Artistic representation of an asteroid. Image source: NASA

«We had a general idea that this asteroid might have come from the Moon, but the overwhelming evidence was that it was rich in silicate minerals—not the kind found on asteroids, but the kind found in lunar rock samples— said Teddy Kareta, an astronomer at the University of California who led the research. “It doesn’t appear to have been in space very long, maybe only a few thousand years or so, since the lack of space weathering has caused its spectrum to redden.”

Asteroid 2024 PT5 was first discovered on August 7, 2024 by the Sutherland Telescope (South Africa), as well as the University of Hawaii’s ATLAS Asteroid Early Warning System. To follow up on this 10th celestial body, the researchers used the Lowell Discovery Telescope in Arizona and NASA’s Infrared Telescope Facility (IRTF) at Mauna Kea Observatory in Hawaii. Scientists studied the sunlight reflected from the asteroid – its spectrum. The spectrum of 2024 PT5 appears to be more consistent with rock samples from the Moon than with known asteroids, such as those from the main belt between Jupiter and Mars.

It was also important to separate the object from space debris left by humanity in near space. The researchers assumed that an empty rocket, when exposed to solar wind, would move like a tin can in the wind. Thus, its drift speed will differ significantly from the speed of movement of the “space brick”. Observations made it possible to accurately calculate the dynamics of the movement of object 2024 PT5 – it behaved like a stone, and not a shell from a rocket or upper stage.

Diagram of the movement of asteroid 2024 PT5 near Earth