Astronomers reveal the most detailed map of asteroid Psyche yet

Enlarge / Astronomers at MIT and elsewhere have mapped the composition of asteroid Psyche, revealing a surface of metal, sand and rock.


Astronomers have produced the most detailed map yet of the surface of 16-Psyche, an asteroid that scientists believe may hold clues to the formation of planets in our solar system. According to a paper published in the Journal of Geophysical Research, 16-Psyche has a highly varied surface of metal, sand, and rock that suggests its history could include metallic eruptions, as well as being hit by other celestial objects. . The asteroid is at the center of NASA’s Psyche mission, launched later this year.

As we reported earlier, 16 Psyche is an M-type asteroid (meaning it has a high metal content) orbiting the Sun in the Main Asteroid Belt, with an unusual apple-shaped shape. earth. The long-held preferred hypothesis is that Psyche is the exposed metallic core of a protoplanet (planetsimal) from the early days of our solar system, with the crust and mantle stripped away by collision (or collisions) with other objects. . In recent years, scientists have concluded that mass and density estimates are not consistent with an all-metal residual core. Rather, it is a complex mixture of metals and silicates.

Alternatively, the asteroid could have once been a parent body for a particular class of stony iron meteorites, one that fragmented and re-accreted into a mixture of metal and silicate. Or maybe it’s an object like 1 Ceres, a dwarf planet in the asteroid belt between the orbits of Mars and Jupiter, except that 16 Psyche may have experienced a period of ferrous volcanism in cooling, leaving highly enriched metals in these volcanic centers.

Scientists have long suspected that metallic cores lurk deep within terrestrial planets like Earth. But those nuclei are buried too far beneath rocky mantles and crusts for researchers to find. As the only metallic core-like body discovered, Psyche offers the perfect opportunity to shed light on how the rocky planets of our solar system (Earth, Mercury, Venus and Mars) may have formed. NASA approved the Psyche mission in 2017, with the intention of sending a spacecraft into orbit around the asteroid and collecting crucial data on its characteristics.

On the left, the map shows surface properties on Psyche, from sandy areas (purple/bottom) to rocky areas (yellow/top). The map on the right shows metal abundances on Psyche, from low (purple) to high (yellow).

Previous mapping efforts have relied on measuring infrared light bouncing off the asteroid’s surface with various telescopes around the world. Last year, astronomers produced a surface map of Psyche with much higher resolution, based on 2019 observational data collected by the 66 radio antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chile.

By combining all of these signals into a single synthetic signal, the team achieved the equivalent resolution of a telescope with a diameter of 16 kilometers (10 miles), or about 20 miles per pixel. This view allowed them to resolve many compositional variations on the asteroid’s surface. They used it to create a thermal emission map of the asteroid’s surface and a high-resolution 3D model of Psyche.

This latest map is based on hundreds of computer-simulated scenarios, each featuring a different combination of surface material composition, taking into account the rotation of the asteroid. The team then compared these simulations to actual thermal emissions in the ALMA data to determine the most likely map of 16-Psyche’s surface.

The results: The asteroid is rich in metals, but the distribution varies across its surface. A similarly varied distribution of silicates suggests that 16-Psyche may once have had a silicate-rich mantle. Additionally, the material at the bottom of the craters changes temperature faster than along the rim as the asteroid rotates. The authors suggest that these craters may have deposits (“ponds”) of fine sand. This is somewhat surprising considering 16-Psyche’s mass and stronger gravity, compared to smaller asteroids that have fine-grained material.

“These data show that the surface of Psyche is heterogeneous, with possible remarkable variations in composition,” said Simone Marchi of the Southwest Research Institute, a co-investigator on the Psyche mission who was not involved in the 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 heterogeneities in composition is something the Psyche science team is eager to investigate. Continued.”

DOI: Journal of Geophysical Research, 2022. 10.1029/2021JE007091/a> (About DOIs).

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