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Scientists were able to see the rock in greater detail, at a resolution of about 30 kilometers per pixel, using the combined power of 66 radio antennas at the Atacama Large Millimeter/submillimeter Array (ALMA) observatory, located in Chile.

Later this year, NASA will launch a tennis-court-sized space probe into the asteroid belt, a region between the orbits of Mars and Jupiter where remnants of the early solar system orbit the Sun. Inside the asteroid belt, the spacecraft will focus on Psyche, a large metal-rich asteroid thought to be the former core of an early planet. The probe, named after its asteroid, will spend about two years orbiting and scanning the surface of the rocky celestial body for clues about the evolution of early planetary bodies.

Before the mission, a team of planetary scientists from the Massachusetts Institute of Technology (MIT), and other research centers, presented in an article, published this Wednesday in the Journal of Geophysical Research: Planets, the most detailed maps yet of the asteroid’s surface, based on observations made by a wide range of ground-based telescopes in northern Chile. The work reveals large metal-rich regions spanning the asteroid’s surface, as well as a large depression that appears to have a different surface texture between the interior and its edge; this difference could reflect a crater filled with finer sand and surrounded by rockier material.

The new maps give clues to the history of the asteroid, named after the goddess Psyche from Greco-Roman mythology. Its rocky regions could be remnants of an ancient mantle – similar in composition to the outermost rock layer of Earth, Mars and the asteroid Vesta – or the imprint of ancient space rock impacts. Craters containing metallic materials support the idea proposed by previous studies that the asteroid may have experienced early eruptions of metallic lava as its former core cooled.

“These maps confirm that metal-rich asteroids are interesting and enigmatic worlds. This is another reason to hope that the Psyche mission will make it to the asteroid,” said Saverio Cambioni of MIT’s Department of Earth, Atmospheric, and Planetary Sciences.

How was the study carried out?

Exploring the massive metallic asteroid that's worth way more than the entire world's economy: What NASA's Psyche mission will look like this year

Worth more than the entire global economy, the surface of Psyche has been the subject of many previous mapping efforts. However, these studies have not been able to spatially resolve the compositional variations on its surface. Cambioni and his colleagues were able to see the asteroid in greater detail, with a resolution of around 30 kilometers per pixel, using the combined power of the 66 radio antennas of the ALMA Observatory (Atacama Large Millimeter/submillimeter Array). Scientists collected data obtained in 2019 by ALMA and converted it into a map of thermal emissions across the asteroid’s surface and produced the latest high-resolution 3D shape model of Psyche. Both studies were published in 2021.

Meanwhile, in the new study, they ran simulations of the rock to see which surface properties might best match and explain the measured thermal emissions. The rotation of the asteroid was modeled and it was measured how the simulated materials on the asteroid would emit thermal emissions. Next, the team looked for the simulated emissions that best matched the actual emissions measured by ALMA. “We did these simulations area by area so that we could capture the differences in surface properties,” Cambioni said.

Main conclusions of the study

The study produced detailed maps of Psyche’s surface, showing that the “facade” of the asteroid is probably covered with a wide variety of materials. The researchers confirmed that in general, the surface of Psyche is rich in metals, but the abundance of metals and silicates varies. This may be a further indication that early in its formation the rock may have had a silicate-rich mantle which has since disappeared.

New Temperature Measurements Confirm Asteroid Psyche Is Worth More Than The Entire World Economy

They also discovered that when the asteroid rotated, the material at the bottom of a large depression – probably a crater – changes temperature much faster than the material at the edge. This suggests that the crater floor is lined with “pools” of fine-grained material, like sand on Earth, that heats up quickly, while the crater rims are made up of rockier, slower-heating material.

“Pools of fine-grained material have been observed on small asteroids, whose gravity is low enough that impacts lift the surface and cause finer material to clump together,” Cambioni explained. “But Psyche is a large body, so if the fine-grained material has accumulated at the bottom of the depression, it’s interesting and somewhat mysterious,” he said.

The original article can be read here

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