Journey to a metallic world: New observations suggest Psyche’s composition different than thought

The Arizona State University-led NASA Psyche mission, which is planned to launch in 2022, will travel to an asteroid named Psyche, orbiting the sun between Mars and Jupiter. This asteroid is of particular interest in that it is rich in metal and may be the exposed nickel-iron core of an early planet, one of the building blocks of the sun’s planetary system.

While we’ll have to wait until the spacecraft arrives at Psyche in 2026 to fully investigate the properties of this unique asteroid, researchers are using the latest high-resolution images, radar measurements and other remote observations to add to our knowledge of the asteroid and prepare for the mission.

In a study recently published in the Journal of Geophysical Research: Planets, lead author Lindy Elkins-Tanton of ASU’s School of Earth and Space Exploration and her team, including ASU researchers Jim Bell, Hannah Bercovici, Steven Dibb and David Williams, analyzed new observations of Psyche’s physical properties and determined that Psyche may be different in composition than originally thought.

“Some years ago, the consensus was that Psyche was almost entirely metal, but this recent compilation of current data indicates that Psyche is a mixture of rock and metal,” said Elkins-Tanton.

For their analysis, the team combined new observations of Psyche including data on density, radar properties and spectral signatures with data from meteorites and models for planetesimal formation.  

While much of the scientific community thought the asteroid was 90% metal on its surface, this data analysis suggests that Psyche’s properties are more likely 30% to 60% metal volume, with the remainder likely composed of low-iron silicate rock.

“There are still contradictions in the compilations of all current data, but they suggest that Psyche is more of a mixture of rock and metal,” said Elkins-Tanton. “If that is the case, this composition may provide additional clues to how Psyche was formed, and perhaps we will discover an unexpected stage of planet formation.”

And as the scientists continue to collect and analyze current data while the spacecraft is being built, there will be an abundance of new understandings of the asteroid once the spacecraft arrives at Psyche in 2026.

The science instruments currently being built to determine what Psyche is made of include a multispectral imager, a gamma ray and neutron spectrometer, and a magnetometer. These instruments will provide high-resolution images, data on elemental composition, and detection and measurement of the asteroid’s magnetic field.

“What’s exciting about space missions is how much more we learn about the mysteries of our solar system when we can get an up-close view,” said Elkins-Tanton. “Our arrival at Psyche in 2026 will be just the beginning of 21 months of orbiting and studying this metallic world.”

About the Psyche mission

Psyche is a metal-rich asteroid orbiting the sun between Mars and Jupiter. As such, it offers a unique look into the violent collisions that created Earth and the terrestrial planets.   

The Psyche spacecraft is planned to launch in August 2022 and travel to the asteroid using solar-electric (low thrust) propulsion. After flying by Mars in 2023 for a gravity assist, the spacecraft will arrive at Psyche in 2026 and spend 21 months orbiting the asteroid, mapping it and studying its properties.

The scientific goals of the Psyche mission are to understand the building blocks of planet formation and explore firsthand a wholly new and unexplored type of world. The mission team seeks to determine whether Psyche is the core of an early planet, how old it is, whether it formed in similar ways to the Earth's core, and what its surface is like.

The spacecraft's instrument payload will include a magnetometer, a multispectral imager, and a gamma ray and neutron spectrometer. The mission will also test a sophisticated new laser communications technology, called Deep Space Optical Communications (DSOC).

The Psyche mission is part of NASA's Discovery Program. Psyche principal investigator is Lindy Elkins-Tanton, professor at ASU’s School of Earth and Space Exploration. Other ASU researchers on the Psyche mission team include Jim Bell (deputy principal investigator and co-investigator), David Williams (co-investigator), and Catherine Bowman (co-investigator and student collaborations lead).

The mission is led by Arizona State University. NASA’s Jet Propulsion Laboratory is responsible for the mission’s overall management, system engineering, integration and test, and mission operations. Maxar Space Solutions, formerly Space Systems Loral, is providing a high-power solar electric propulsion spacecraft chassis.