The remarkable terrain of the asteroid Bennu. Credit: NASA’s Goddard Space Flight Center
The rocky surface of the asteroid Bennu provides protection against small meteoroid impacts, according to crater observations from the OSIRIS-REx spacecraft (Origins, Spectral Interpretation, Resource Identification, Security Rule Explorer). NASA. OSIRIS-REx traveled to the asteroid Bennu near Earth and is carrying a small sample to Earth to study it. The mission was launched on September 8, 2016 from Cape Canaveral Air Force Station. The spacecraft arrived in Bennu in 2018 and will return to Earth for a sample in 2023.
“These observations provide a new insight into how asteroids like Bennu respond to energy impacts,” said Edward (Beau) Bierhaus of Lockheed Martin Space, Littleton, Colorado, lead author of an article in this month’s issue of Nature Geoscience. .
Bennu is a “run-down” asteroid, meaning it was formed from the remains of a much larger asteroid that was destroyed by an ancient impact. Fragments of the collision joined under its own weak gravity to form Bennu.
The team used unprecedented high-resolution global data sets to examine Bennu craters: images from the OSIRIS-REx camera suite and surface height data (topography) derived from the OSIRIS-REx laser altimeter. a laser measuring instrument (lidar). in the spaceship.
This image shows the rocky surface of the asteroid Bennu. It was taken by the PolyCam camera of NASA’s OSIRIS-REx spacecraft on April 11, 2019, from a distance of 2.8 miles (4.5 km). The field of view is 211 feet (64.4 m) and the large rock in the upper right corner of the image is 50 feet (15.4 m) high. When the image was taken, the spacecraft was over the southern hemisphere, pointing PolyCam far to the north and west. Credit: NASA / Goddard / University of Arizona
“Measuring craters and their population in Bennu was exceptionally exciting,” said David Trang, of the University of Hawaii at Mānoa, Honolulu, co-author of the paper. “At Bennu, we discovered something unique about small, rocky bodies, which expanded our knowledge of impacts.”
Planetary scientists can estimate the age of surfaces by measuring the abundance and size of craters. Impact craters accumulate over time, so a surface with many craters is older than a surface with few craters. In addition, the size of the crater depends on the size of the impactor, with larger impactors usually making larger craters. Because small meteoroids are much more abundant than large ones, celestial objects such as asteroids tend to have many more small craters than large ones.
Bennu’s largest craters follow this pattern, with the number of craters decreasing as their size increases. However, for craters less than 6.6 to 9.8 feet (about 2 to 3 meters) in diameter, the trend is backward, with the number of craters decreasing as their size decreases. This indicates that something unusual is happening on the surface of Bennu.
Researchers believe that Bennu’s block profusion acts as a shield, preventing many small meteoroids from forming craters. Instead, these impacts are more likely to break the blocks or shavings and fracture them. In addition, some impactors that manage to traverse the rocks make smaller craters than if the surface of Bennu were covered with smaller, uniform particles, such as sand from the beach.
This activity causes the Bennu surface to change differently from objects with solid or fine-grained surfaces. “The displacement or disruption of a small individual or group of blocks by a small impact is probably one of the fastest processes of action on the surface of a asteroid of debris. In Bennu, this helps to make the surface look like many times younger than the interior, “Bierhaus said.
Reference: “Crater population on asteroid (101955) Bennu indicates armored impact and a young surface” by EB Bierhaus, D. Trang, RT Daly, CA Bennett, OS Barnouin, KJ Walsh, R.-L. Ballouz, WF Bottke, KN Burke, ME Perry, ER Jawin, TJ McCoy, HC Connolly Jr., MG Daly, JP Dworkin, DN DellaGiustina, PL Gay, JI Brodbeck, J. Nolau, J. Padilla, S. Stewart, S Schwartz, P. Michel, M. Pajola and DS Lauretta, April 7, 2022, Nature Geoscience.DOI: 10.1038 / s41561-022-00914-5
Learn more about the mission and team:
The research was supported by NASA under the New Frontiers Program and the OSIRIS-REx Participating Scientist Program, the Canadian space agency, the French space agency, the Italian space agency, the research program and Horizon 2020 innovation of the European Union and the Academies of Excellence. of the Joint, Excellent and Dynamic Excellence Initiative of the Université Côte d’Azur.
Dante Lauretta of the University of Arizona, Tucson, is the principal investigator for OSIRIS-REx. The University of Arizona also leads the OSIRIS-REx scientific team and mission-based scientific observation planning and data processing, and created the OSIRIS-REx camera suite. NASA’s Goddard Space Flight Center in Greenbelt, Maryland offers comprehensive mission management, systems engineering and security and mission assurance for OSIRIS-REx. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and offers flight operations. The OSIRIS-REx Laser Altimeter was provided by the Canadian Space Agency. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Scientific Mission Management at NASA’s Washington, DC headquarters. .