The varied surface of asteroid Psyche suggests a dynamic history, which could include metallic eruptions, asteroid-shaking impacts, and a lost rocky mantle.
Later this year, probe the size of a tennis court to the asteroid belt, a region between the orbits of metal-rich asteroid that is thought to be the ancient core of an early planet. The probe, named after its asteroid target, will then spend close to two years orbiting and analyzing Psyche’s surface for clues to how early planetary bodies evolved.
Ahead of the mission, which is led by principal investigator Lindy Elkins-Tanton ’87, SM ’87, PhD ’02, planetary scientists at
Overall, Psyche’s surface was found to be surprisingly varied in its properties.
The new maps hint at the asteroid’s history. Its rocky regions could be vestiges of an ancient mantle — similar in composition to the rocky outermost layer of Earth, Mars, and the asteroid Vesta — or the imprint of past impacts by space rocks. Finally, craters that contain metallic material support the idea proposed by previous studies that the asteroid may have experienced early eruptions of metallic lava as its ancient core cooled.
“Psyche’s surface is very heterogeneous,” says lead author Saverio Cambioni, the Crosby Distinguished Postdoctoral Fellow in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “It’s an evolved surface, and these maps confirm that metal-rich asteroids are interesting, enigmatic worlds. It’s another reason to look forward to the Psyche mission going to the asteroid.”
Cambioni’s co-authors are Katherine de Kleer, assistant professor of planetary science and astronomy at Caltech, and Michael Shepard, professor of environmental, geographical, and geological sciences at Bloomsburg University.
The surface of Psyche has been a focus of numerous previous mapping efforts. Researchers have observed the asteroid using various telescopes to measure light emitted from the asteroid at infrared wavelengths, which carry information about Psyche’s surface composition. However, these studies could not spatially resolve variations in composition over the surface.
Cambioni and his colleagues instead were able to see Psyche in finer detail, at a resolution of about 20 miles per pixel, using the combined power of the 66 radio antennas of the Atacama Large Millimeter/submillimeter Array (a 2021 study. Those same data were used by Shepard to produce the most recent high-resolution 3D shape model of Psyche, also published in 2021.
On the left, this map shows surface properties on Psyche, from sandy areas (purple/low) to rocky areas (yellow/high). The map on the right shows metal abundances on Psyche, from low (purple) to high (yellow).
To catch a match
In the new study, Cambioni ran simulations of Psyche to see which surface properties might best match and explain the measured thermal emissions. In each of hundreds of simulated scenarios, he set the asteroid’s surface with different combinations of materials, such as areas of different metal abundances. He modeled the asteroid’s rotation and measured how simulated materials on the asteroid would give off thermal emissions. Cambioni then looked for the simulated emissions that best matched the actual emissions measured by ALMA. That scenario, he reasoned, would reveal the likeliest map of the asteroid’s surface materials.
“We ran these simulations area by area so we could catch differences in surface properties,” Cambioni says.
The study produced detailed maps of Psyche’s surface properties, showing that the asteroid’s façade is likely covered in a large diversity of materials. The researchers confirmed that, overall, Psyche’s surface is rich in metals, but the abundance of metals and silicates varies across its surface. This may be a further hint that, early in its formation, the asteroid may…