For two months late last year, Earth had a captured mini-moon, before it went back on its way around the sun. And now NASA said on January 22, 2025, that the little asteroid – named 2024 PT5 – is likely a chunk of our moon broken off in a past collision. A team of researchers believe the rock’s composition means a large impact ejected it from the moon’s surface.
The researchers published their peer-reviewed findings in Astrophysical Journal Letters on January 14, 2025.
Mini-moon was a piece of our moon
Teddy Kareta of Lowell Observatory in Arizona was lead author of the study. Kareta said:
We had a general idea that this asteroid may have come from the moon, but the smoking gun was when we found out that it was rich in silicate minerals. Not the kind that are seen on asteroids but those that have been found in lunar rock samples. It looks like it hasn’t been in space for very long, maybe just a few thousand years or so, as there’s a lack of space weathering that would have caused its spectrum to redden.
The researchers used the Lowell Discovery Telescope and the NASA Infrared Telescope Facility on Mauna Kea in Hawai’i to analyze the light reflected from the asteroid. That light didn’t match any known asteroid type. But it did look like what we know of the composition of our moon.
Analyzing the orbit of 2024 PT5
In addition to looking at the spectrum and composition of asteroid 2024 PT5, the researchers also analyzed the object’s orbit. They ruled out the object being space junk by how it was affected by solar radiation pressure. These little particles from our sun can give objects a push. Space debris, such as hollow rocket boosters, move more due to this push than natural objects such as asteroids. Co-author Oscar Fuentes-Muñoz of JPL said:
Space debris and space rocks move slightly differently in space. Human-made debris is usually relatively light and gets pushed around by the pressure of sunlight. That 2024 PT5 doesn’t move this way indicates it is much denser than space debris.
The 2nd asteroid from the moon
This is only the second asteroid known to come from the moon. In 2016, astronomers discovered asteroid 469219 Kamo’oalewa. While it also had an orbit similar to Earth’s, it never became a temporary mini-moon like 2024 PT5 did. Astronomers hope to find more asteroids from the moon, and maybe even match them to the craters they were ejected from. Kareta said:
This is a story about the moon as told by asteroid scientists. It’s a rare situation where we’ve gone out to study an asteroid but then strayed into new territory in terms of the questions we can ask of 2024 PT5.
Earth had an asteroid mini-moon for 2 months
Asteroid 2024 PT5 was a mini-moon of Earth from September 29 until November 25, 2024. However, the asteroid never completed one revolution of Earth, so it was considered a temporarily captured flyby as opposed to a temporarily captured orbiter. Asteroid PT5 is approximately 33 feet (10 meters) in size.
The ATLAS survey in South Africa discovered the asteroid on August 7, 2024.
Newly-discovered #asteroid 2024 PT5 is about to undergo a "mini-moon event" when its geocentric energy becomes negative from September 29 – November 25.https://t.co/sAo1qSRu3J pic.twitter.com/pVYAmSbkCF
— Tony Dunn (@tony873004) September 10, 2024
Asteroid mini-moon animation via Tony Dunn on X.
How did we get the asteroid mini-moon?
Asteroid 2024 PT5’s close approach to our planet at a relatively low velocity allowed Earth’s gravity to temporarily alter its path. But the sun eventually pulled it back into a heliocentric orbit. The asteroid had another somewhat close flyby of Earth on January 9, 2025, before:
leaving the neighborhood of Earth shortly afterward, until its next return in 2055.
Bottom line: Earth had an asteroid mini-moon late last year for two months. Now scientists say that the mini-moon was likely a chunk of our moon ejected in an impact.
Source: On the Lunar Origin of Near-Earth Asteroid 2024 PT5
Source: A Two-month Mini-moon: 2024 PT5 Captured by Earth from September to November
Read more: Say goodbye to Earth’s mini-moon on February 1 and 2
The post Earth’s asteroid mini-moon a chunk of the moon? first appeared on EarthSky.
from EarthSky https://ift.tt/fC6gDIA
For two months late last year, Earth had a captured mini-moon, before it went back on its way around the sun. And now NASA said on January 22, 2025, that the little asteroid – named 2024 PT5 – is likely a chunk of our moon broken off in a past collision. A team of researchers believe the rock’s composition means a large impact ejected it from the moon’s surface.
The researchers published their peer-reviewed findings in Astrophysical Journal Letters on January 14, 2025.
Mini-moon was a piece of our moon
Teddy Kareta of Lowell Observatory in Arizona was lead author of the study. Kareta said:
We had a general idea that this asteroid may have come from the moon, but the smoking gun was when we found out that it was rich in silicate minerals. Not the kind that are seen on asteroids but those that have been found in lunar rock samples. It looks like it hasn’t been in space for very long, maybe just a few thousand years or so, as there’s a lack of space weathering that would have caused its spectrum to redden.
The researchers used the Lowell Discovery Telescope and the NASA Infrared Telescope Facility on Mauna Kea in Hawai’i to analyze the light reflected from the asteroid. That light didn’t match any known asteroid type. But it did look like what we know of the composition of our moon.
Analyzing the orbit of 2024 PT5
In addition to looking at the spectrum and composition of asteroid 2024 PT5, the researchers also analyzed the object’s orbit. They ruled out the object being space junk by how it was affected by solar radiation pressure. These little particles from our sun can give objects a push. Space debris, such as hollow rocket boosters, move more due to this push than natural objects such as asteroids. Co-author Oscar Fuentes-Muñoz of JPL said:
Space debris and space rocks move slightly differently in space. Human-made debris is usually relatively light and gets pushed around by the pressure of sunlight. That 2024 PT5 doesn’t move this way indicates it is much denser than space debris.
The 2nd asteroid from the moon
This is only the second asteroid known to come from the moon. In 2016, astronomers discovered asteroid 469219 Kamo’oalewa. While it also had an orbit similar to Earth’s, it never became a temporary mini-moon like 2024 PT5 did. Astronomers hope to find more asteroids from the moon, and maybe even match them to the craters they were ejected from. Kareta said:
This is a story about the moon as told by asteroid scientists. It’s a rare situation where we’ve gone out to study an asteroid but then strayed into new territory in terms of the questions we can ask of 2024 PT5.
Earth had an asteroid mini-moon for 2 months
Asteroid 2024 PT5 was a mini-moon of Earth from September 29 until November 25, 2024. However, the asteroid never completed one revolution of Earth, so it was considered a temporarily captured flyby as opposed to a temporarily captured orbiter. Asteroid PT5 is approximately 33 feet (10 meters) in size.
The ATLAS survey in South Africa discovered the asteroid on August 7, 2024.
Newly-discovered #asteroid 2024 PT5 is about to undergo a "mini-moon event" when its geocentric energy becomes negative from September 29 – November 25.https://t.co/sAo1qSRu3J pic.twitter.com/pVYAmSbkCF
— Tony Dunn (@tony873004) September 10, 2024
Asteroid mini-moon animation via Tony Dunn on X.
How did we get the asteroid mini-moon?
Asteroid 2024 PT5’s close approach to our planet at a relatively low velocity allowed Earth’s gravity to temporarily alter its path. But the sun eventually pulled it back into a heliocentric orbit. The asteroid had another somewhat close flyby of Earth on January 9, 2025, before:
leaving the neighborhood of Earth shortly afterward, until its next return in 2055.
Bottom line: Earth had an asteroid mini-moon late last year for two months. Now scientists say that the mini-moon was likely a chunk of our moon ejected in an impact.
Source: On the Lunar Origin of Near-Earth Asteroid 2024 PT5
Source: A Two-month Mini-moon: 2024 PT5 Captured by Earth from September to November
Read more: Say goodbye to Earth’s mini-moon on February 1 and 2
The post Earth’s asteroid mini-moon a chunk of the moon? first appeared on EarthSky.
from EarthSky https://ift.tt/fC6gDIA
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