A glimpse of asteroid Psyche, provided by a NASA telescope array in Chile, hints at a very lively history for the body that includes metallic eruptions, asteroid impacts and even a now-lost rocky mantle.
Psyche is the target of an upcoming NASA mission later this year. Meanwhile, a probe will spend nearly two years in orbit analyzing Psyche to help us better understand how it formed. As such, the asteroid is naturally attracting the attention of astronomers around the world eager to gather as much data about it as possible for the next mission.
As part of the effort, a trio of American researchers used readings from an array of telescopes in northern Chile to create the most detailed map yet of the asteroid’s surface properties. The map reveals stretches of metal-rich areas on Psyche, as well as a Great Depression that may give us a glimpse through its surface into the ancient mantle below.
A turbulent history
“The surface of Psyche is very heterogeneous,” says lead author Saverio Cambioni, 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 and enigmatic worlds. This is another reason to look forward to the Psyche mission heading to the asteroid.
The featured face of Psyche suggests that this celestial body has had quite a dynamic history, the team explains. Its surface characteristics are surprisingly varied for a asteroid its sizethey add, and each offers a unique clue to what Psyche has been through.
The rocky outcrops of Psyche could be the remnants of an ancient rocky mantle similar in composition to the outer layers of Earth or Mars. That being said, until we get a better look, we won’t know for sure; they could also be remnants of past impacts with space rocks. What the team is quite confident in are the metal structures of Psyche. They support previous theories that the asteroid likely experienced metallic lava eruptions during its early days before its core cooled and hardened.
Although the composition of Psyche’s surface has been widely studied in the past, using telescopes that peer into infrared light reflected from the body, researchers have had great difficulty using this data in a meaningful way in the past. . The main problem was to solve the spatial variations of composition on the surface of the asteroid; in other words, we knew what materials its surface was made of, but we didn’t know what material went where.
The team was able to overcome this limitation and map Psyche in greater detail than ever before – at around 20 miles per pixel – by aggregating data obtained from 66 Atacama Large Millimeter/submillimeter Array (ALMA) radio antennas into the northern Chile. This data collection was obtained on June 19, 2019, when ALMA focused its entire lineup on Psyche.
“Signals from ALMA antennas can be combined into a synthetic signal equivalent to a telescope with a diameter of 16 kilometers (10 miles),” says co-author Katherine de Kleer, assistant professor of planetary sciences and astronomy at Caltech. . “The larger the telescope, the higher the resolution.”
On June 19, 2019, ALMA focused its entire network on Psyche as it tossed and turned in the asteroid belt. De Kleer collected data during this time and converted it into a map of thermal emissions across the asteroid’s surface, which the team reported in a 2021 study. This same data was used by Shepard to produce the newest high resolution 3D shape model of Psyche, also released in 2021.
The final step of the research was to run a series of simulations to see which distribution of surface properties would best match the thermal emissions obtained by ALMA. Such simulations assumed different combinations of materials on Psyche’s surface, such as different abundances of various metals. The team performed these simulations “area by area,” says Cambioni, to allow greater precision in the process.
Overall, the team reports that the asteroid’s face is likely rich in metals, although the ratios of metals and silicates vary quite significantly across its surface. Another interesting finding is that as the asteroid rotates, the material inside a large depression changes temperature much faster than that around the edge, suggesting that the bottom of this structure is covered in slabs of fine-grained material like sand, while the edges are made of rockier material.
“Pools of fine-grained material have been observed on small asteroids, whose gravity is low enough that impacts shake the surface and cause finer material to accumulate,” says Cambioni. “But Psyche is a large body, so if fine-grained material accumulates at the bottom of the depression, it’s interesting and somewhat mysterious.”
“These data show that the surface of Psyche is heterogeneous, with possible remarkable variations in composition,” said Simone Marchi, a scientist at the Southwest Research Institute and co-investigator of NASA’s Psyche mission, who was not involved in the study. current study. “One of the main objectives of the Psyche mission is to study the composition of the asteroid’s surface using its gamma-ray and neutron spectrometer and a color imager. Thus, the possible presence of compositional heterogeneities is something the Psyche Science team is eager to investigate further.
The article “The heterogeneous surface of the asteroid (16) Psyche” was published in the Journal of Geophysical Research: Planets.
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