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An artist’s concept of asteroid 16 Psyche. Credit: Maxar/ASU/P.Rubin/NASA/JPL-Caltech
The widely studied metallic asteroid 16 Psyche has long been believed to be the exposed iron core of a small planet that failed to 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 hints at a much different origin story.
Scientists are interested in 16 Psyche because if its supposed origins are correct, it would provide an opportunity to study an exposed planetary core up close. NASA is scheduled to launch its Psyche mission in 2022 and reach the asteroid in 2026.
University of Arizona undergraduate David Cantello is the lead author of a new research paper published in The Planetary Science Journal that suggests 16 Psyche is 82.5% metallic, 7% low-iron pyroxene and 10.5% carbonaceous chondrites likely to be produced about collisions from other asteroids. Cantillo and his collaborators estimate that 16 Psyche’s volume density – also known as porosity, which refers to the amount of empty space there is inside its body – is about 35%.
These estimates differ from previous analyzes of 16 Psyche’s composition that led researchers to estimate that it could contain up to 95% of the mineral and be more dense.
“This decrease in mineral content and bulk density is interesting because it shows that 16 psyches are more modified than previously thought,” Cantelo said.
Rather than being the intact exposed core of an early planet, it may actually be more like a pile of rubble, similar to another carefully studied asteroid – Bennu. UArizona leads the science mission team for NASA’s OSIRIS-REx mission, which retrieved a sample from the surface of Bennu that is now making its way back to Earth.
“A breath as a pile of rubble would be very unexpected, but our data continue to show estimates of low density despite its high mineral content,” Cantello said.
Asteroid 16 Psyche is the size of Massachusetts, and scientists estimate that it contains about 1% of all the material of the asteroid belt. First discovered by an Italian astronomer in 1852, it was the 16th asteroid ever.
“Having a lower mineral content than previously thought means the asteroid may have had collisions with asteroids containing the more common carbonaceous chondrites, which deposited a surface layer that we’re watching,” Cantelo said. This was also observed on the asteroid Vesta by NASA’s Dawn spacecraft.
Asteroid 16 Psyche has been valued at $10,000 quadrillion ($10,000 followed by 15 extra zeros), but the new findings could slightly underestimate the iron-rich asteroid’s value.
“This is the first paper to put some specific limitations on its surface content,” Cantelo said. “Previous estimates were a good start, but this improves these numbers a bit more.”
Another well-studied asteroid, Bennu, contains a lot of carbonaceous chondrite and has a porosity of over 50%, a classic characteristic of a rubble 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 boulders and boulders from clumping together too tightly. But for a 16-breath body to be so porous, that’s unexpected.
“The opportunity to study an exposed core from a small planet is extremely rare, which is why they’re sending a spacecraft mission there, but our work shows that 16 psyches are more interesting than expected,” Cantelo said.
Previous estimates of 16 Psyche’s composition were made by analyzing sunlight reflected off its surface. Match the light pattern with other metal objects. Instead, Cantelo and his colleagues recreated 16 Psyche regolith – or soft, rocky surface material – by mixing different materials in the lab and analyzing the light patterns until they matched the telescope’s observations of the asteroid. Only a few laboratories in the world practice this technique, including the UArizona Lunar and Planetary Laboratory and the Johns Hopkins Laboratory of Applied Physics in Maryland, where Cantelo worked while in high school.
“I’ve always been interested in space,” said Cantello, who is also president of the UArizona Astronomical Club. “I knew astronomy studies would be heavy on computers and observations, but I like to do more hands-on work, so I wanted to connect my studies with geology in some way. I major in geology and major in planetary science and mathematics.”
“David’s paper is an example of the cutting-edge research work done by our undergraduate students,” said study co-author Vishnu Reddy, associate professor of planetary sciences who heads the lab where Cantillo works. “It’s also a good example of a collaborative effort between undergraduates, graduate students, postdoctoral fellows, and staff in my lab.”
The researchers also believe that the carbonaceous material on 16 Psyche’s surface is water-rich, so they will then work to combine data from ground-based telescopes and spacecraft missions to other asteroids to help determine how much water is present.
Study provides a more complete view of the massive asteroid Psyche More information: David C. Cantillo et al, Restriction of regolith formation of the asteroid (16) Psyche via in vitro visible infrared spectroscopy, Journal of Planetary Science (2021). DOI: 10.3847 / PSJ / abf63b Provided by University of Arizona
Quote: Asteroid 16 Psyche may not be what scientists expected (2021, June 9) Retrieved June 9, 2021 from https://phys.org/news/2021-06-asteroid-psyche-scientists.html
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