Tiny Craters on Bennu Boulders Reveal Asteroid’s Age

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Boulder on Bennu's Surface

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SwRI and the University of Arizona studied centimeter- to meter-sized craters on stones spread around the surface area of the near-Earth asteroid Bennu. This composite reveals the cascading rim of an ancient crater from the time Bennu lived in the asteroid belt. The overlaid colors highlight the topography of the stone with warmer colors showing greater elevations. Credit: University of Arizona/Johns Hopkins APL/York University

Scientists presumed Bennu’s layover in the inner Solar System at 1.75 million years.

Last year NASA snagged a sample from the surface area of asteroid Bennu, an Empire State Building-sized body that Southwest Research Institute researchers have actually assisted map with almost unmatched accuracy. Using orbital information from the OSIRIS-REx spacecraft, scientists determined centimeter- to meter-sized craters on the stones spread around its rugged surface area to clarify the age of the asteroid.

While the gathered sample will yield huge clinical worth when it is gone back to Earth in 2023, an essential task for researchers throughout the time in orbit at Bennu was to comprehend the geology of the whole asteroid to offer essential context for the sample. This offers insights into all the procedures that may have impacted the nature of the sample.

“The amazing data collected by OSIRIS-REx at asteroid Bennu have allowed us to not just find impact craters across its surface, but to actually find and study the craters on the surfaces of boulders,” stated SwRI’s Dr. Kevin Walsh, a coauthor of “Bennu’s near-Earth lifetime of 1.75 million years inferred from craters on its boulders,” released in the journal Nature. “The craters that we could observe and measure on the surfaces of boulders allowed us to estimate their strengths, a first-of-its-kind measurement.”

Bennu is a dark debris stack held together by gravity and believed to be an asteroid residue produced following an accident including a bigger main-belt things. Boulders are spread throughout its greatly cratered surface area, showing that it has had a rough-and-tumble life because being freed from its much bigger moms and dad asteroid millions or perhaps billions of years back. Scientists usage research studies of effect craters to figure out the ages of planetary surface areas.

Team members from the University of Arizona established a mathematical formula that enables scientists to compute the optimum effect energy a stone of a provided size and strength might withstand prior to being smashed.

Walsh, lead author Dr. Ron Ballouz (a postdoctoral fellow at the University of Arizona), and coworkers united an understanding of the variety of craters, the strength of the products affected, and the varieties of impactors to assist constrain the chronology of Bennu’s presence in the inner Solar System at 1.75 million years. Since the spacecraft reached Bennu in 2018, researchers have actually been defining the asteroid’s structure from orbit and comparing it to other asteroids and meteorites. Now NASA has actually gathered a real sample of its surface area that researchers will have the ability to study.

“We held our breath as the spacecraft touched the asteroid’s boulder-strewn surface with a robotic arm for a few seconds to collect a sample of rocks and dust on October 20 — a first for NASA,” Walsh stated. “Hitting pay dirt on the first attempt is fantastic. We look forward to learning so much more when the sample arrives back at Earth in 2023.”

The manuscript explains an approach for determining the strength of strong items utilizes remote observations of craters on surface area stones. Determining the strengths of stones on asteroid surface areas is a leap forward from determining the strength of much smaller sized meteorites, which have the predisposition of making it through passage through Earth’s environment.

“The rocks tell their history through the craters they accumulated over time,” stated Ballouz. “The boulders serve as witnesses to Bennu’s time as a near-Earth asteroid, validating decades of dynamical studies of the lifetime of near-Earth asteroids.”

For more on this research study, read Impact Craters on Bennu’s Rugged Surface: Asteroid’s Scars Tell Stories of Its Past.

Reference: “Bennu’s near-Earth lifetime of 1.75 million years inferred from craters on its boulders” by R.-L. Ballouz, K. J. Walsh, O. S. Barnouin, D. N. DellaGiustina, M. Al Asad, E. R. Jawin, M. G. Daly, W. F. Bottke, P. Michel, C. Avdellidou, M. Delbo, R. T. Daly, E. Asphaug, C. A. Bennett, E. B. Bierhaus, H. C. Connolly Jr, D. R. Golish, J. L. Molaro, M. C. Nolan, M. Pajola, B. Rizk, S. R. Schwartz, D. Trang, C. W. V. Wolner and D. S. Lauretta, 26 October 2020, Nature.
DOI: 10.1038/s41586-020-2846-z



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