This year NASA is going to launch a tennis court-sized probe to the asteroid belt between the orbits of Mars and Jupiter; where the remnants of the early solar system revolve around the sun. Once the probe reaches the asteroid belt, it will lock onto Psyche, a large, metal-rich asteroid believed to be the ancient core of an early planet. In fact, the probe itself is named after the asteroid and will spend about two years in orbit analyzing how early planetary bodies evolved.
But ahead of the mission, planetary scientists produced the most detailed maps of the asteroid’s surface to date. These maps are based on observations made by a large number of ground-based telescopes in northern Chile. The maps show extensive metal-rich regions on 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 potentially be a crater filled with finer sand and surrounded by more rocky material.
The research team presented the maps in a research paper titled “The Heterogeneous Surface of Asteroid (16) Psyche” published in JGR Planets.
In general, the surface of Psyche turned out to be surprisingly diverse in its properties. The maps also hint at the history of the asteroid. The rocky regions on it may be the remains of an ancient mantle similar in composition to the rocky outer layer of Earth, Mars, and the asteroid Versa. On the other hand, it could also be related to past space rock impacts.
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Previous research has put forward the idea that the asteroid may have experienced early metallic lava eruptions as its ancient core cooled. Craters containing metallic material support this idea. The surface of Psyche has been the focus of many previous cartographic works. The researchers observed the asteroid using various telescopes to measure the infrared light emitted by the asteroid, which provides information about the composition of Psyche’s surface. However, until recently, these studies could not spatially resolve compositional variations on the surface.
The researchers used the combined power of 66 Atacama Large Millimeter/submillimeter Array (ALMA) radio antennas in northern Chile. Each of these antennas measures the light emitted by an object at millimeter wavelengths; in a range sensitive to temperature and certain electrical properties of surface materials.
On June 19, 2019, ALMA focused its entire array on Psyche as it orbited the asteroid belt. The researchers collected data from this period and converted it into a map of thermal radiation on the asteroid’s surface, which the team reported in a study published in 2021. In another study published the same year, the team used this data to create the most recent high-resolution 3D model of Psyche.
In the latest study, the researchers ran Psyche simulations to see which surface properties might best fit and explain the thermal radiation that had been measured previously. The researchers identified the asteroid’s surface with various combinations of materials, such as areas with different metal content. They simulated the asteroid’s rotation and measured how the simulated materials on the asteroid would emit thermal radiation. They then looked for simulated emissions that best matched the actual emissions previously measured by ALMA.