Science

Interstellar objects may have fallen on the moon

A new paper suggests that at least one interstellar object (ISO) has likely crashed into Earth’s moon over eons.

Thus, the Moon, filled with thousands of craters, is a good hunting ground for objects originating from interstellar space, the authors suggest using statistics and modeling.

“Given the number of ISOs we expect to see in the Solar System, there are likely a few craters that were created by very high ISO speeds throughout the Solar System, and probably one or two on the Moon,” lead author. This was reported to Space.com by Sam Cabot, Ph.D. at Yale University.

However, the challenge is to find such a crater in the first place.

Related: Interstellar comet Borisov shines in incredible new Hubble photos

computer-generated image of an interstellar object as a swarm of debris flying through space

This simulation depicts the interstellar object ‘Oumuamua as a mass of fragments elongated by stellar tidal forces. (Image credit: ZHANG Yun/von ESO/M. Kornmesser)

ISOs are comets or asteroids that originated outside of our solar system. So far, only two have been confirmed: “Oumuamua and Borisov.” A new study suggests that we can learn more about the composition of these mysterious objects if we can track a crater on the Moon formed by an interstellar collision.

Decades of observations of our nearest large neighbor, especially with NASA’s Lunar Reconnaissance Orbiter, have yielded high-definition maps that will be used in NASA’s Artemis program. The Artemis program aims to land humans on the moon in the late 2020s if all goes according to plan.

However, the maps can only provide as much information about the craters as they are shown, the authors say. The problem is that maps provide little spectroscopic information about the composition of craters. While some analysis can be done from orbit, the authors say it will likely take “ground truth” to determine if the crater was indeed formed from ISO, Cabot said.

Related: Amazing photos of the moon from NASA’s Lunar Reconnaissance Orbiter

polar view of the moon filled with craters

The South Pole of the Moon is one of the most attractive places in the entire solar system. This mosaic was taken from the wide angle camera on NASA’s Lunar Reconnaissance Orbiter. (Image credit: NASA/Arizona State University)

Cabot added that it would be difficult to predict what the astronauts might find, as the two ISOs already discovered are very different from each other. Borisov is most similar to other objects of the solar system known to us; however, according to him, astronomers were surprised by how much carbon monoxide is present in its composition. ‘Oumuamua is even more mysterious, he says, because there is no “satisfactory theory” to fully explain its composition.

Cabot explained that something emanated from ‘Oumuamua’s surface and caused it to accelerate as it left our solar system and headed into interstellar space.

“The difficulty,” he continued, “is that we in the community have been observing with space telescopes, looking for typical gases that you would expect to evaporate from the surface of astronomical objects. None of them have been found with certainty.”

Because astronomers have not been able to find typical outgassing products such as water, Cabot says they instead think there are unique kinds of volatiles on the object’s surface. (Volatiles are chemical elements and compounds that evaporate relatively easily.) To better understand what isocyanates are made of in general, the Moon could provide one place to collect specific evidence, he added.

Related: Photographers capture ‘ridiculously detailed image’ of moon for NASA Artemis 1 launch

starship on the surface of the moon with the crescent of the earth behind

NASA hopes to land humans on the moon by the end of the decade. (Image credit: SpaceX)

Moreover, relatively soon boots may appear on the surface of the Moon. Provided that the funding and technological development of the Artemis program goes according to plan, people can look for sources of craters within their landing site.

The problem, however, is that it’s impossible to predict exactly where an ISO might land. In addition, human expeditions will be limited to the south pole of the moon for the time being; this is where NASA and other space agencies hope to send their astronauts in the near future.

However, according to Cabot, human missions “give us many opportunities to characterize regolith, [meaning] find out the composition of the lunar soil and try to answer questions about the early solar system.”

Related: How did the solar system form?

The planets of the solar system are lined up in the illustration, the sun is on the left. A comet flies overhead and the asteroid belt between Mars and Jupiter is visible

Solar system, not to scale. (Image credit: NASA)

What little we know about IOS suggests one strong hypothesis about how these craters might be different, he says. ISOs tend to move at higher speeds than other objects in our solar system. This is because objects tied to the sun have a sort of “speed limit” due to the sun’s gravity.

“ISOs that are free-flowing throughout the galaxy can enter the solar system at much higher speeds,” Cabot said. “So that was the premise of our paper: to investigate the signatures of extremely high speed collisions.”

Astronomers have chosen a top speed of 225,000 miles per hour (360,000 km/h) because solar system objects rarely reach that speed. The authors speculate that melting signatures at the impact site may be greater at this elevated velocity, although the composition of the melt will depend on the composition of the rock in the area.

Further, according to Cabot, “a widely accepted description of the lunar regolith that we hope to see with Artemis” is needed. The problem, he continued, is that astronauts and their equipment will need to figure out how to process large volumes of regolith from the Moon in order to make a meaningful comparison with what an ISO might contain.

Related: NASA Artemis 1 Lunar Mission Explained in Photos

comet object with degassing in artist's view

An artist’s idea of ​​what the surface of the interstellar comet 2I/Borisov might look like. (Image credit: M. Kormesser/ESO)

Some of NASA’s future robotic landing missions could serve as test drives for large-scale regolith processing. NASA has a program called Commercial Lunar Payload Services (CLPS) that aims to place private landers and payloads on the Moon to support the Artemis missions. Cabot said some of these payloads may treat regolith as a secondary target compared to other scientific studies.

Meanwhile, the authors, along with the rest of the astronomical community, are still looking for other ISOs with powerful wide-angle telescopes. And that search will get a boost in the near future when instruments like the Vera S. Rubin observatory go online.

An article based on the study was published in the Planetary Science Journal. (will open in a new tab). A preview is available on Archive. (will open in a new tab)

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