Rowan geology chair co-authors series of articles ahead of asteroid sample’s return to Earth

The extraterrestrial payload of a NASA spacecraft is still about a year away from Earth but researchers, including Rowan University Geology Chair Dr. Harold Connolly Jr., are already publishing widely about the distant capture of materials from a moving asteroid.

In 2020, spacecraft OSIRIS-REx rendezvoused with and performed a touch-and-go retrieval mission just above the surface of Bennu, a near-Earth asteroid about 500 meters wide and 200 million miles away. The craft dropped a robotic arm, expelled a burst of nitrogen to loosen the surface, and captured about 250 grams of material.

The craft’s mission has been extended but in September 2023 it will eject its payload while orbiting Earth for retrieval by NASA scientists.

Connolly will be a lead investigator of the payload once it reaches Earth but he and others on the research team have begun publishing widely on the mission and its early results, from findings about the composition of Bennu to a breakdown of the process to collect materials from it.

On May 23, the team published a cover story in the journal Nature Geoscience, “Alignment of fractures on Bennu’s boulders indicative of rapid asteroid surface evolution,” which reviewed early geological findings from the asteroid.

On July 7, the journal Science Advances carried the article, “Near-zero cohesion and loose packing of Bennu’s near subsurface revealed by spacecraft contact,” which discussed the surprisingly loose nature of the asteroid’s surface. The same day, the journal Science ran the article, “Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu,” which detailed how “the sampling event mobilized rocks and dust into a debris plume,” essentially sucking up materials while excavating a nine-meter-long crater.

Connolly said early findings have been surprising but illuminating, from the looseness of the so-called “rubble pile” asteroid to the way the spacecraft performed its deep space mission.

“Part of what we learned by collecting the sample on this rubble pile asteroid is they’re loosely held together, even more loosely than sand on a beach,” said Connolly, a co-investigator and mission sample scientist on the OSIRIS-REx mission.

He said though the carbonaceous asteroid is hurtling through space as a seemingly unified body (which in fact has a slight risk of striking Earth over the next 200 years) it is loosely composed, held together by microgravity.

“Everything that has mass has gravity,” he said. “The question is, how much mass is there and how much gravity is exerted? We think of Earth as a solid rock. The asteroid is 50 percent porous space and every grain is exerting its own bit of gravity on its neighbors.”

He said among early findings the most important may be that Bennu is much looser than what scientists expected but he said the pristine sampling of an asteroid in space – as opposed to what they can learn from meteorites that breach Earth’s atmosphere and reach the surface – has much more to reveal including, possibly, clues to how planets formed in the first place.

“One of the most important questions is 'what is the origin of life?'” he said. “Well, you need water, oxygen, an atmosphere. You can’t have any of that until you have a planet.”

Connolly, who teaches in Rowan’s School of Earth & Environment and is also a co-investigator with the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 mission, said many of the lessons from his space work make their way into the classroom.

“Every week I give students updates on both missions,” he said. “My entire minerology and petrology course is based around how we explore space.”