The widely studied metallic asteroid known as 16 Psyche was thought to be the exposed iron core of a small planet that did not form during the early days of the solar system. But new research led by the University of Arizona suggests that the asteroid may not be as metallic or dense as previously thought and suggests a very different origin story.
Scientists are interested in 16 Psyche because, if its supposed origins are true, it would provide an opportunity to closely study an exposed planetary core. NASA is scheduled to launch its Psyche mission in 2022 and reach the asteroid in 2026.
Arizona graduate student David Cantillo is the lead author of a new article published in The Journal of Planetary Sciences proposed by 16 Psyche is 82.5% metal, 7% low iron pyroxene, and 10.5% carbonaceous chondrite that was likely released by impacts from other asteroids. Cantillo and his collaborators estimate that the apparent density of 16 Psyche, also known as porosity, which refers to the amount of empty space found in your body, is around 35%.
These estimates differ from previous analyzes of the composition of 16 Psyche, which led the researchers to estimate that it could contain up to 95% metal and be much denser.
“This drop in metal content and bulk density is interesting because it shows that 16 Psyche is more modified than previously thought,” Cantillo said.
Rather than being an intact exposed core from a primitive planet, it may actually be closer to a pile of debris, similar to another fully studied asteroid: Bennu. Urizona leads the science mission team for NASA’s OSIRIS-REx mission, which recovered a sample from Bennu’s surface that is now returning to Earth.
“A psyche like a rubble heap would be very unexpected, but our data continues to show low density estimates despite its high metallic content,” Cantillo said.
Asteroid 16 Psyche is about the size of Massachusetts and scientists estimate that it contains about 1% of all material in the asteroid belt. First spotted by an Italian astronomer in 1852, it was the 16th asteroid ever discovered.
“Having a lower metal content than previously thought means that the asteroid could have been exposed to collisions with asteroids containing the most common carbonaceous chondrites, which deposited a surface layer that we are seeing,” Cantillo said. This was also observed on the asteroid Vesta by NASA’s Dawn spacecraft.
Asteroid 16 Psyche was estimated at $ 10,000 trillion ($ 10,000 followed by another 15 zeros), but the new discoveries may slightly devalue the iron-rich asteroid.
“This is the first article that establishes some specific restrictions on its surface content. The previous estimates were a good start, but this refines those numbers a bit more, ”Cantillo said.
The other well-studied asteroid, Bennu, contains a large amount of carbonaceous chondrite material and has a porosity of more than 50%, which is a classic feature of a debris pile.
This high porosity is common for relatively small, low-mass objects like Bennu, which is as large as the Empire State Building, because a weak gravitational field prevents the object’s rocks and boulders from being compressed too much. But for an object the size of 16 Psyche to be so porous is unexpected.
“The opportunity to study an exposed nucleus of a planetesimal is extremely rare, so they are sending the spacecraft mission there,” Cantillo said, “but our work shows that Psyche 16 is much more interesting than expected.”
Previous estimates of the composition of 16 Psyche were made by analyzing sunlight reflected off its surface. The light pattern matched that of other metal objects. Instead, Cantillo and his collaborators recreated the regolith 16 Psyche, or loose material from the rock surface, mixing different materials in a laboratory and analyzing the light patterns until they matched the telescope’s observations of the asteroid. There are only a few labs in the world that practice this technique, including the Lunar and Planetary Laboratory in Arizona and the Johns Hopkins Applied Physics Laboratory in Maryland, where Cantillo worked during high school.
“I’ve always been interested in space,” said Cantillo, who is also president of the UArizona Astronomy Club. “I knew that astronomy studies would depend on computers and observation, but I like to do more practical work, so I wanted to connect my studies with geology in some way.”
“David’s article is an example of the cutting-edge research work done by our graduation student“Said study co-author Vishnu Reddy, an associate professor of planetary science who runs the lab where Cantillo works.” It is also a good example of the collaborative effort between undergraduate, graduate, postdoc, and my lab staff. “
The researchers also believe that the carbonaceous material on the surface of 16 Psyche is rich in water, so they will next work to merge data from ground-based telescopes and spacecraft missions with other asteroids to help determine the amount of water present.
David C. Cantillo et al, Constraining the Regolith Composition of Asteroid (16) Psyche via Laboratory Visible Near-Infrared Spectroscopy, The Journal of Planetary Sciences (2021). DOI: 10.3847 / PSJ / abf63b
University of Arizona
Appointment: Asteroid 16 Psyche May Not Be What Scientists Expect (2021, June 9) Retrieved June 9, 2021 from https://phys.org/news/2021-06-asteroid-psyche-scientists.html
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