When the asteroid Psyche is first imaged up close by a NASA spacecraft, scientists expect to find a lot of metals. This could be the iron-rich interior of an early planetary building block that was stripped of its outer rocky shell as it repeatedly collided with other large bodies during the early formation of the Solar System.
New research by scientists at NASA’s Ames Research Center in Silicon Valley, California, suggests that this is exactly what the Psyche mission will find.
SOFIA’s involvement
The team observed Psyche in February 2022 using NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA). The observatory is a Boeing 747SP airplane modified to carry a reflector telescope. As a flying telescope, SOFIA collected data that is not affected by the lower layers of the Earth’s atmosphere and made observations from around the world, including over the oceans.
For the first time, SOFIA was able to collect data from every part of Psyche’s surface. This also allowed the team to collect data on the materials that make up Psyche’s surface – information that could not be collected using ground-based telescopes.
The scientists studied how different wavelengths of light are reflected from Psyche. To observe the asteroid, the researchers used a mid-infrared camera that detects wavelengths in the middle of the electromagnetic spectrum. They measured its emissivity (the amount of energy it emits) and porosity (how many tiny holes or spaces an object has). Both characteristics can give clues about the materials that make up an object.
A metal body
The team noticed that the data on Psyche’s emissivity was mostly flat, meaning that its spectra had no peaks or other noticeable features – that is, a chart or graph that shows the intensity of light emitted by an asteroid in a certain energy range. Similar flat spectra were found in laboratory conditions when mid-infrared devices were used on metal objects. This led the researchers to the conclusion that Psyche is probably a metallic body.
Notably, the team did not observe a spectral feature called the 10-micron plateau, which usually indicates a “fluffy” surface like that of lunar regolith. Previous studies of Psyche have identified this feature, suggesting that there may be differences between the surface at Psyche’s north pole, which was facing Earth during the team’s study, and the surface at its south pole, which has been the focus of previous research.
The scientists also speculated that the regolith at the south pole observed by other researchers may have been ejected by a collision elsewhere on Psyche’s surface. This idea is supported by past observations of Psyche, which have found evidence of huge depressions and impact craters throughout the asteroid.
“With this analysis and previous studies of Psyche, we have reached the limit of what astronomical observations can tell us about this fascinating asteroid,” said Maggie McAdam, principal investigator.
NASA/Frank Michaux
Close study
According to her, it is now necessary to physically visit Psyche to study it up close and learn more about what appears to be a very unique planetary body.
NASA’s mission to Psyche will provide this opportunity. The spacecraft is scheduled to launch on October 12, 2023. It will arrive at the asteroid in 2029 and stay in its orbit for at least 26 months.
Psyche’s potential to answer many questions about planet formation is a key reason why it was chosen for close observation by the spacecraft.
Metal cores of planets
Scientists believe that planets such as Earth, Mars, and Mercury have metallic cores, but they are buried too deep beneath the planets’ mantles and crusts to be seen or measured directly. If Psyche is confirmed to be a planet’s core, it could help scientists understand what is inside the Earth and other large planetary bodies.
The size of Psyche is also important for deepening scientific knowledge of Earth-like planets. It is the largest M-type (metallic) asteroid in our solar system. This means that Psyche is likely to show differentiation, where materials inside the planet separate from each other, with the heaviest materials sinking to the middle and forming cores.
The scientists’ conclusions suggest that the asteroid is very complex and likely hides many other surprises. The possibility of surprises is one of the most exciting parts of the upcoming Psyche mission.
