The widely studied metal asteroid, known as 16 Psyche, has long been thought to have discovered the iron core of a small planet that failed to form in the earliest days of the solar system. But a new study conducted by the University of Arizona suggests that the asteroid may not be as metallic or dense as once thought, and hints at a very different history of origin.
Scientists are interested in 16 Psyche, because if its origin is assumed to be correct, it would provide an opportunity to study an open planetary core up close. NASA is scheduled to launch its Psyche mission in 2022 and arrive on the asteroid in 2026.
UArizona student David Cantillo is the lead author of a new article published in Journal of Planetary Science this suggests 16 Psyche is 82.5% metal, 7% low iron pyroxene and 10.5% carbon chondrite, which was probably supplied by impacts from other asteroids. Cantilo and his colleagues estimate that the volume density of 16 Psyche – also known as porosity, which refers to how much empty space is in his body – is about 35%.
These estimates differ from previous analyzes of the composition of 16 Psyche, which led researchers to estimate that it may 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,” Cantilo said.
Instead of being an intact discovered nucleus on an early planet, it may actually be closer to a pile of rubble, like another well-studied asteroid, Bennu. UArizona is leading NASA’s OSIRIS-REx scientific mission team, which took a sample from Bennu’s surface, which is now returning to Earth.
“The psyche as a pile of debris would be very unexpected, but our data continue to show low-density estimates despite its high metal content,” Cantilo said.
The Asteroid 16 Psyche is the size of Massachusetts and scientists estimate that it contains about 1% of the total material of an asteroid belt. First spotted by an Italian astronomer in 1852, it is the 16th asteroid ever discovered.
“The presence of a lower metal content than previously thought means that the asteroid could have been exposed to collisions with asteroids containing the more common carbon chondrites that deposit the surface layer we observe,” Cantilo said. This was also observed on the asteroid Vesta by the NASA Dawn spacecraft.
Asteroid 16 Psyche is valued at $ 10,000 quadrillion ($ 10,000, followed by another 15 zeros), but new discoveries may slightly devalue the iron-rich asteroid.
“This is the first article to place some specific restrictions on its surface content. Earlier assessments were a good start, but it improves those figures a little more,” Cantilo said.
The other well-studied asteroid, Bennu, contains a lot of carbon chondrite and has a porosity of over 50%, which is a classic feature of a pile of debris.
Such high porosity is common for relatively small and low-mass objects such as Bennu – which is as large as the Empire State Building – because the weak gravitational field prevents the rocks and stones from being placed too tightly on the object. But for an object of size 16 Psyche to be so porous is unexpected.
“The ability to study the open nucleus of a planetesimal is extremely rare, so they send the spacecraft mission there,” Cantilo said, “but our work shows that 16 Psyche is much more interesting than expected.”
Past estimates of the composition of 16 Psyche have been made by analyzing the sunlight reflected from its surface. The pattern of light matched that of other metal objects. Instead, Cantilo and his collaborators recreated Psyche’s regolith 16 – or loose rock material – by mixing different materials in a laboratory and analyzing light patterns until they matched the asteroid’s telescopic observations. There are only a few laboratories in the world that practice this technique, including UArizona’s Lunar and Planetary Laboratory and John Hopkins’ Applied Physics Laboratory in Maryland, where Cantilo worked while in high school.
“I’ve always been interested in space,” said Cantilo, who is also president of the UArizona Astronomical Club. “I knew that studying astronomy would be difficult for computers and observation, but I like to do more practical work, so I wanted to somehow connect the research with geology. I specialize in geology and a minority in planetary science and mathematics.”
“David’s report is an example of cutting-edge research done by our students,” said study co-author Vishnu Reddy, an associate professor of planetary science who runs the laboratory where Cantilo works. “It’s also a great example of a collaborative effort between students, undergraduates, PhD students and staff in my lab.”
Researchers also believe that the carbon material on the surface of 16 Psyche is rich in water, so the next job will be to combine data from ground-based telescopes and spacecraft missions with other asteroids to determine the amount of water available.
The study offers a more complete view of the massive asteroid psyche
David C. Cantillo et al, Limiting the composition of the regolith of the asteroid (16) Psyche by laboratory visible near-infrared spectroscopy, Journal of Planetary Science (2021). DOI: 10.3847 / PSJ / abf63b
Provided by the University of Arizona
Quote: Asteroid 16 Psyche may not be what scientists expected (2021, June 9), extracted on June 9, 2021 from https://phys.org/news/2021-06-asteroid-psyche-scientists. html
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