Most detailed maps of asteroid Psyche reveal an ancient world of rock and metal

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NASA is set to launch a probe the size of a tennis court to the asteroid belt between the orbits of Mars and Jupiter this year; where the remnants of the early solar system circle the sun. After the probe reaches the asteroid belt, it will zero in on Psyche, a large, metal-rich asteroid that is thought to be the ancient core of an early planet. In fact, the probe itself is named after the asteroid and will spend close to two years orbiting and analysing how early planetary bodies evolved.

But ahead of the mission, planetary scientists have prepared the most detailed maps of the asteroid’s surface to date. These maps are created based on the observations taken by a large array of ground telescopes in northern Chile. The maps show vast metal-rich regions across the asteroid’s surface, along with a large depression that appears to have a different surface texture between the interior and its rim. This difference could potentially be a crater filled with finer sand and rimmed with rockier material.

The research team presented the maps in a research article titled, “The Heterogeneous Surface of Asteroid (16) Psyche,” published in the journal JGR Planets.

Overall, Psyche’s surface was revealed to be surprisingly varied in its property. The maps also hint at the asteroid’s history. The rocky regions on it could be the vestiges of an ancient mantle, similar composition to the rocky outermost layer of Earth, Mars and the asteroid Versa. On the other hand, it could also be from past impacts made by space rocks.

Previous studies have proposed the idea that the asteroid may have experienced early eruptions of metallic lavas as its ancient core cooled. The craters that contain metallic material support this idea. Psyche’s surface has been a focus of many previous mapping efforts, Researchers have observed the asteroid using various telescopes to measure the 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 until recently.

The researchers used the combined power of 66 radio antennae of the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. Each of these antennae measures light emitted from an object at millimetre wavelengths; within a range that is sensitive to temperature and certain electrical properties of surface materials.

ALMA focused its entire array on Psyche on June 19, 2019, as it orbited and rotated within the asteroid belt. The researchers collected data during this period and converted it into a map of thermal emissions across the asteroid’s surface, which the team reported in a study published in 2021. In another study published during the same year, the team used this data to create the most recent high-resolution 3D shape model of Psyche.

In the latest study, the researchers ran simulations of Psyche to see which surface properties could best match and explain the thermal emissions that were measured earlier. The researchers set the asteroid’s surface with different combinations of materials such as areas of different metal abundancies. They modelled the asteroid’s rotation and measured how simulated materials on the asteroid would give off thermal emissions. They then looked for the simulated emissions that best matched the actual emissions measured earlier by ALMA.

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