Artist’s 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.
Credit: Addy Graham/University of Arizona.

Metal-rich Near-Earth asteroids are being eyed as potential mining targets.

New research, for example, underscores the value of asteroid 1986 DA, loaded with iron, nickel, cobalt, and platinum-group metals (PGM). Those characteristics present on the asteroid would exceed the global reserves of these metals here on Earth.

In fact, if 1986 DA is mined and the metals marketed over 50 years, the annual value of precious metals for this object would be roughly $233 billion.

This new appraisal stems from research published in the Planetary Science Journal, titled “Physical Characterization of Metal-rich Near-Earth Asteroids 6178 (1986 DA) and 2016 ED85,” work led by Juan Sanchez of the Planetary Science Institute in Tucson, Arizona.

NASA Infrared Telescope Facility (IRTF).
Credit: Institute for Astronomy, University of Hawaii

The paper’s findings are based on observations from the NASA Infrared Telescope Facility on the island of Hawaii. The work was funded by the NASA Near-Earth Object Observations Program, which also funds that facility.

Meteorite relationship

“Metal-rich near-Earth asteroids (NEAs) represent a small fraction of the NEA population that is mostly dominated by S- and C-type asteroids,” the paper explains. “Because of this, their identification and study provide us with a unique opportunity to learn more about the formation and evolution of this particular type of bodies, as well as their relationship with meteorites found on Earth.”

Credit: JPL’s Solar System Dynamics (SSD) website

Sanchez and colleagues present near-infrared (NIR) spectroscopic data of NEAs 6178 (1986 DA) and 2016 ED85. Contrary to 1986 DA, there are no radar data available for 2016 ED85. For this reason, in the present study this object is considered as a candidate metal-rich body.

“Our analysis shows that both NEAs have surfaces with 85 percent metal such as iron and nickel and 15 percent silicate material, which is basically rock,” said lead author Sanchez in a University of Arizona statement. “These asteroids are similar to some stony-iron meteorites such as mesosiderites found on Earth.”

Mesosiderites have been found to have similar pyroxene chemistry and produced a good spectral match when metal was added, suggesting similarities between the parent body of the NEAs and the parent body of these meteorites.

Exposed cores

Pointed out in the research paper is that metal-rich asteroids are thought to represent the exposed cores of differentiated asteroids whose crusts and mantles were stripped away following a catastrophic disruption.

Credit: NASA/Arizona State University

A more recent theory suggests that some of these objects, in particular asteroid Psyche, might still preserve a rocky mantle, and that the metal present on the surface could be the result of ferrovolcanic eruptions that covered the rocky material with liquid.

Indeed, asteroid 16 Psyche is thought to be the largest metal-rich body in the solar system, situated in the main asteroid belt between the orbits of Mars and Jupiter rather than near Earth. This space rock is the target of NASA’s Psyche mission.

Psyche is set to launch next year, marking the first time NASA has set out to explore an asteroid projected to be richer in metal than rock or ice.

Credit: Juan Sanchez, et al.

Compositional survey

Some of the largest known metal-rich asteroids are located in the middle and outer part of the asteroid belt.

“We started a compositional survey of the NEA population in 2005, when I was a graduate student, with the goal of identifying and characterizing rare NEAs such as these metal-rich asteroids,” said Vishnu Reddy, a University of Arizona planetary science associate professor and principal investigator of the NASA grant that funded the just-published work. “It is rewarding that we have discovered these ‘mini Psyches’ so close to the Earth,” he said in the University of Arizona statement

To access the paper — “Physical Characterization of Metal-rich Near-Earth Asteroids 6178 (1986 DA) and 2016 ED85,” go to:

https://iopscience.iop.org/article/10.3847/PSJ/ac235f/pdf

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