An artist impression of a close flyby of the metal-rich Near-Earth asteroid 1986 DA. Astronomers using the NASA Infrared Telescope Facility have confirmed that the asteroid is made of 85% metal. (Addy Graham/University of Arizona)
Metal asteroids offer something rare in the solar system — the core of a planet without all the rock that normally surrounds it.
Since it is impossible to directly examine a planetary or lunar core if the parent body remains intact, metal-rich asteroids where the upper mantle and crust layers have been lost to a cataclysmic crash offer a potential path to, in effect, peek inside the depths (and deep time) of an object.
The asteroid Psyche is such an object, and that’s why NASA approved a mission to the asteroid that is scheduled to launch next year. Orbiting the sun between Mars and Jupiter in the largest asteroid belt, Psyche appears to be the exposed nickel-iron core of an early planet, and as such reveals the early evolution of our solar system.
But Psyche is not the only metal-rich asteroid known to astronomers, and it certainly is not the closest.
Two much smaller “mini-Pysches” have been detected that are also comprised of iron, nickel, and other metals ranging from platinum to rare earth elements. And these two mini-asteroids — 1986 DA and 2016 ED85 — were recently found to have their spectral signatures are quite similar to asteroid Psyche.
And unlike Psyche, which is between 180 million and 360 million miles away, these mini-Psyches orbit less than twenty million from Earth every 20 to 30 years.
“These kind of metal-rich Near-Earth asteroids are extremely rare,” said Vishnu Reddy of the University of Arizona, and co-author of a recent paper in Planetary Science Journal. “There are some 27,000 known Near-Earth objects, and only these two are metal rich. Of the 1.2 million asteroids that have been identified, only a little over a dozen are in that metal-rich category.”
Reddy has been part of a group researching unusual near-Earth objects since 2005, and so these findings are most rewarding.
“In the years ahead we can study Psyche, a large metal-rich object that is quite far away,” Reddy said. “And now we also know of two much smaller metal-rich objects that are also much, much closer to us.”
Artist’s conception of Psyche, with orbiter spacecraft. The mission, led by Linda Elkins-Tanton at Arizona State University, is scheduled to launch next year.
