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OSIRIS-REx snags more than enough asteroid stuff

The leaders of NASA’s OSIRIS-REx mission to the asteroid Bennu, more than 200 million miles from Earth, say they’ve collected an overflowing amount of rocks and dust to bring back home.

Camera views of the probe’s sample collection head — captured on Oct. 22, two days after the collection maneuver — showed particles slowly escaping into space, through small gaps where rocks have wedged the container’s lid in an open position.

Based on what they’re seeing, scientists have concluded that they captured more than the 2 ounces (60 grams) of material that was considered the minimum requirement for mission success. The best guess is that the probe grabbed as much as 14 ounces (400 grams)

To make sure they maximize the return, team members are working to stash the disk-shaped head in its return capsule as soon as possible.

“The loss of mass is of concern to me,” the University of Arizona’s Dante Lauretta, principal investigator for the $800 million mission, said today in a news release. For that reason, the mission team decided to forgo a maneuver that would have involved spinning the probe and determining its moment of inertia, in order to get a better estimate of how much extra mass the sample added to the spacecraft.

“We were almost a victim of our own success,” Lauretta said.

Thomas Zurbuchen, NASA’s associate administrator for science, said he’s “so excited to see what appears to be an abundant sample that will inspire science for decades beyond this historic moment.”

“Bennu continues to surprise us with great science and also throwing a few curveballs,”  Zurbuchen said. “And although we may have to move more quickly to stow the sample, it’s not a bad problem to have.”

This week’s sample collection maneuver — known as a touch-and-go, or TAG — served as the climax of a mission that began with the van-sized spacecraft’s launch in 2016. OSIRIS-REx arrived at Bennu two years ago and conducted a detailed survey, to prepare for the TAG as well as to study the 1,600-foot-wide asteroid’s composition in detail.

OSIRIS-REx carefully smashed its collection head into Bennu’s crumbly surface on Oct. 20. Scientists say the collection head ended up plunging 10 to 20 inches (24 to 48 centimeters) into Bennu’s crust. The head was beneath the surface for a mere six seconds, but that was enough time for a puff of nitrogen gas to blast a flurry of gravel and dirt into OSIRIS-REx’s dust catcher.

If the mission schedule holds true, OSIRIS-REx will fire its thrusters for the return trip next March, and drop off its precious sample capsule over the Utah desert during a flyby in September 2023.

OSIRIS-REx is an Egyptian-sounding acronym that actually stands for “Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer.”  Bennu was chosen as the mission’s target because it’s rich in the carbon-bearing compounds that are thought to have served as the chemical building blocks for life on Earth.

Scientists hope that studying the sample up close will yield new insights into the origin of the solar system and the workings of astrobiology. The mission is also designed to help scientists figure out what kinds of resources could be extracted from asteroids, and what strategies would work best if a potentially hazardous asteroid ever had to be diverted.

By Alan Boyle

Mastermind of Cosmic Log, contributing editor at GeekWire, author of "The Case for Pluto: How a Little Planet Made a Big Difference," president of the Council for the Advancement of Science Writing. Check out "About Alan Boyle" for more fun facts.

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