Scientists peer inside an asteroid – is Beanu in the process of making its pieces?


This series of images taken by the OSIRIS-REx spacecraft shows Benue in a full rotation from a distance of about 50 miles (80 km). The spacecraft’s Polycam camera received thirty-six 2.2 millisecond frames over a period of four hours and 18 minutes. Credit: NASA’s Goddard Space Flight Center / University of Arizona

New findings from NASA’s OSIRIS-REX mission suggest that the asteroid Bennu’s interior may be weaker and less dense than its outer layers – such as a crème-filled chocolate egg flight into space.

The results appear in a study published in the journal Science advance And led by University of Colorado Boulder Osiris-Rex The team, consisting of Professor Daniel Shehr and Jay McMahon. The findings may give scientists new insights into the evolution of asteroids in the solar system – how bodies like beanu change over millions of years or longer.

OSIRIS-REX met in late 2018, with Beanu orbiting the sun more than 200 million miles from Earth. Since then, the spacecraft built by Colorado-based Lockheed Martin has studied the object in more detail than any other asteroid. History of Space Exploration.

However, until now, one question remains elusive: what is inside?

Benu orbit diagram

Diagram of Benu’s orbit in relation to Earth and other planets. Credit: NASA / Goddard / University of Arizona / Lockheed Martin

The skiers of the mission’s radio science team, McMahon and his colleagues now feel they have an answer — or at least a part. Using OSIRIS-REX’s own navigational devices and other equipment, the group spent nearly two years mapping the ebay and flow of Bibu’s gravitational field. Think of it as taking an X-ray of a portion of space debris with an average width about the height of the Empire State Building.

“If you can measure the gravitational field with sufficient accuracy, the place where the mass is located creates a hard barrier, even if you can’t see it directly,” said Andrew French, one of the new studies Co-student and a former graduate student at CU Boulder, now NASAJet Propulsion Laboratory (JPL).

What the team has found could also be a problem for Benue. The asteroid’s core appears to be weaker than its exterior, a fact that could threaten its existence in the not too distant future.

“You can probably imagine in a million years or less the whole flying thing,” said Sheeres, a distinguished professor in the Ann and HJ Smade Department of Aerospace Engineering Sciences.

Development of asteroids

Of course, this is part of the fun of studying asteroids. Sherese explained that Benue belongs to a class of small bodies called what scientists call a “debris pile” asteroid – as his name suggests, consisting of loosely held-off debris.

Asteroids also change over time than people think.

“None of them are unchanged since the dawn of the solar system,” Sherose said. “They are replaced by things like sunlight that affect how they spin and collide with other asteroids.”

To study how Bennu and other similar asteroids could change, however, he and his colleagues needed to peek inside.

Asteroid Bennu Crystals

On January 19, 2019, OSIRIS-REX saw small pieces of material leaping from the surface of the asteroid Bennu. Credit: NASA / Goddard / University of Arizona / Lockheed Martin

The team was lucky from here. When OSIRIS-REX first arrived at Bennu, the spacecraft appeared somewhat unusual: repeated, small objects, some small-sized boulders, which looked off into the asteroid and into space. In many cases, those particles circled Benue before falling back to the surface. Members of the mission’s radio science team at JPL were witnesses to how the body’s gravity worked for the first time — a bit like Isaac Newton’s Aprophal story referring to the existence of gravity after the observation of an apple falling on its head Does.

“It was a bit like someone was on the surface of the asteroid and throwing these stones so that they could be tracked,” Shehr said. “Our partners can estimate the gravitational field of the particles that carried those particles.”

Squishy center

In the new study, Sherees and his colleagues combined those records of Benue’s gravity in work with OSIRIS-REX data — accurate measurements of how the asteroid pierced the spacecraft over a period of months. He made some surprising discoveries: before the mission began, many scientists had assumed that Benue would have a homogenous interior. As Glass said, “A pile of rocks is a pile of rocks.”

But gravitational field measurements suggested something different. To explain those patterns, some parts of Benue’s interior would need to be packed more tightly than others. And some of the least densest spots in the asteroid were on its equator and around a different bulge at its core.

“It seems like there is a void in its center, within which you can fit a pair of football fields,” Shehr said.


Now, thanks to laser ultimetry data and high-resolution imagery from OSIRIS-REX, we can tour the remarkable terrain of Benue. Credit: NASA’s Goddard Space Flight Center

The asteroid’s spin may be responsible for that void. Scientists know that the asteroid is rotating faster and faster over time. Speed ​​can build up, Scheeres said, slowly pushing the material away from the asteroid’s center and toward its surface. Benue may, in other words, be in the process of spinning itself into pieces.

“If the density of its core is low, it may be easy to separate the entire asteroid,” Sheeshes said.

For the scientist, the new findings are bitwatches: after measuring Benue’s gravitational field, Scheer and his team have mostly wrapped up their work on the OSIRIS-REx mission.

Their results have contributed to the mission’s sample analysis plan – currently in development. The returned samples will be analyzed to determine cohesion between grains – a key physical property that affects the mass distribution observed in their studies.

“We were hoping to find out what happened to this asteroid over time, which can give us a better idea of ​​how all these small asteroids are being transformed into millions, crores, or millions of years.” Shiroz said. “Our findings exceeded our expectations.”

For more information on this and related research read the asteroid Beanu mystery unlocked by NASA’s OSIRIS-REX Ahead of Historic Heist.

DJ Skares, AS French, p. Tricarico, SR Chesley, Y. Takahashi, d. “Mass distribution of debris-pile asteroids (101955) Benue” by Fernochia, JW McMahon, DN Brack, AB Davis, R-L-L. . Balluz, E.R. Jouin, b. Rositis, JP Emery, AJ Ryan, RS Park, BP Rush, Ann. Mastrodemos, BM Kennedy, J. Belrose, D.P. Lube, d. Velez, AT Vaughan, JM Leonard, J. Geraert, b. . Page, p. Entresian, e. Mazariko, K. Getzandner, d. Rowlands, MC Morrow, J. Small, D. Highsmith, s. Gosens, EE Palmer, JR Weirich, RW Raskell, OS Barnoin, MG Daly, JA Seabrook, MM Al Assad, LC Filpot, CL Johnson, CM Hertelle, VE Hamilton, p. Mitchell, KJ Walsh, MC Nolan and DS Loretta, 8 October 2020 Science advance.
DOI: 10.1126 / Sciadv.abc3350

The University of Arizona leads the science operations for OSIRIS-REx. NASA’s Goddard Space Flight Center in Maryland manages the overall mission.

Other coauthors of the new study include researchers from the Jet Propulsion Laboratory, Smithsonian Institution, The Open University, Northern Arizona University, Canatex Aerospace, Inc., NASA Goddard Space Flight Center, University of Maryland, Johns Hopkins University, York University, University of the University Huh. British Columbia, Southwest Research Institute, Université Côte d’Azur, and University of Arizona.

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