A small object near Earth has been identified as a lunar rock

The small object 2024 PT5, discovered last year near Earth but not orbiting it, was probably ejected into space after an impact on Earth. Luna thousands of years ago.

As described in a study published in Astrophysical Journal Letters, researchers have gathered more evidence that 2024 PT5 — which measures about 10 meters across — is of local origin: It appears to be composed of rock broken off from the Moon’s surface and ejected into space after a large impact.

“We had a general idea that this asteroid could have come from the Moon, but the irrefutable proof was when we discovered that it was rich in silicate minerals, not the type seen in asteroids, but those that have been found in samples of lunar rocks,” Teddy Kareta, an astronomer at Lowell Observatory in Arizona, who led the research, said in a statement. “It appears that it hasn’t been in space for very long, perhaps only a few thousand years or so, as there is a lack of space erosion that would have caused its spectrum to redden.”

The asteroid was first detected on August 7, 2024 by the NASA-funded Sutherland, South Africa telescope of the University of Hawaii’s Asteroid Terrestrial Impact Latest Alert System (ATLAS). Kareta’s team then used observations from the Lowell Discovery Telescope and NASA’s Infrared Telescope (IRTF) at the Mauna Kea Observatory in Hawaii to show that the spectrum of sunlight reflected by the surface of the small object did not match that of no known type of asteroid; instead, the reflected light more closely matched the Moon’s rock.

A second clue emerged by observing how the object moves. Along with asteroids, Space Age debris, such as old rockets from historic launches, can also be found in Earth-like orbits.

The difference in their orbits has to do with how each type responds to the pressure of solar radiation, which comes from the momentum of photons (quantum particles of light from the Sun) that exert a minuscule force when they hit a solid object in space. This exchange of momentum of many photons over time can push an object back and forth very slightly, speeding it up or slowing it down. While a man-made object, such as a hollow rocket booster, will move like an empty can in the wind, a natural object, such as an asteroid, will be much less affected.

To rule out 2024 PT5 as space junk, scientists at NASA’s Center for Near-Earth Object Studies (CNEOS), which is managed by the agency’s Jet Propulsion Laboratory in Southern California, analyzed its motion. . Their precise calculations of the object’s motion under the force of gravity eventually allowed them to look for additional motion caused by the pressure of solar radiation. In this case, the effects were found to be too small for the object to be artificial, showing that 2024 PT5 is most likely of natural origin.

“Space debris and space rocks move slightly differently in space,” said Oscar Fuentes-Muñoz, a co-author of the study and a NASA postdoctoral fellow at JPL working with the CNEOS team. “Man-made debris is usually relatively light and moves under the pressure of sunlight. “The fact that 2024 PT5 is not moving in this direction indicates that it is much denser than space debris.”