NASA’s OSIRIS-REx spacecraft leaves the surface of the asteroid Bennu after collecting a sample. Credit: Goddard Space Flight Center from NASA / CI Lab / SVS
Scientists have learned something surprising after analyzing the data collected when NASA’s OSIRIS-REx spacecraft collected a sample of the asteroid Bennu in October 2020. The spacecraft would have sunk into the asteroid if he had not fired his thrusters to retreat immediately after taking his dust sample. and rock from the surface of Bennu.
“Our expectations about the asteroid’s surface were completely wrong.” – Dante Lauretta, principal investigator of OSIRIS-REx
Unexpectedly, it turns out that the particles that make up Bennu’s exterior are so lightly packaged and lightly bound together that if a person stepped on the asteroid they would feel very little resistance. It would be like getting into a well of plastic balls that are popular play areas for kids.
“If Bennu were completely full, that would involve an almost solid rock, but we found a lot of empty space on the surface,” said Kevin Walsh, a member of the OSIRIS-REx scientific team at Southwest Research Institute, based in San . Antonio.
Side-by-side images of NASA’s OSIRIS-REx spacecraft of the robotic arm as it descended to the surface of the asteroid Bennu (left) and as it touched it to shake dust and rock for collection of samples (right). OSIRIS-REx landed in Bennu at 18:08 EDT on October 20, 2020. Credit: NASA’s Goddard Space Flight Center
The latest findings on the Bennu surface were published on July 7, 2022 in a couple of articles in the journals Science and Science Advances, edited respectively by Dante Lauretta, principal investigator at OSIRIS-REx, based at the University of Arizona, Tucson, and Kevin. Walsh. These startling results add to the intrigue that has trapped scientists throughout the OSIRIS-REx mission, as Bennu has proven to be consistently unpredictable.
The first surprise presented by the asteroid was in December 2018, when the NASA spacecraft arrived in Bennu. The OSIRIS-REx team found a rough surface full of blocks instead of the smooth, sandy beach they had been waiting for according to ground and space telescope observations. The researchers also discovered that Bennu was expelling rock particles from its surface into space.
“Our expectations about the asteroid’s surface were completely wrong,” Lauretta said.
The last clue that Bennu was not what it appeared occurred after the OSIRIS-REx spacecraft collected a sample and transmitted stunning close-up images of the asteroid’s surface to Earth. “What we saw was a huge wall of rubble radiating from the sample site,” Lauretta said. “We were like, ‘holy cow!'”
The asteroid Bennu, close to Earth, is a pile of rock debris and blocks left over from the formation of the solar system. On October 20, 2020, NASA’s OSIRIS-REx spacecraft briefly landed on Bennu and collected a sample to return to Earth. During this event, the spacecraft’s arm sank much deeper into the asteroid than expected, which confirmed that Bennu’s surface is bound smoothly. Now, scientists have used OSIRIS-REx data to review the sample collection event and better understand how loose top layers of Bennu are held together. Credit: Goddard Space Flight Center from NASA / CI Lab / SVS
Scientists on the mission were perplexed by the abundance of scattered pebbles, given the smoothness with which the spacecraft touched the surface. Even stranger was that the spacecraft left a large crater 26 feet (8 meters) wide. “Every time we tried the sample collection procedure in the lab, we barely made a divot,” Lauretta said. The mission team decided to send the spacecraft back to take more photographs of the Bennu surface “to see the great disaster we did,” Lauretta said.
The researchers analyzed the volume of debris visible in the images before and after the sample site, nicknamed “Nightingale.” They also analyzed the acceleration data collected during the spacecraft landing. These data revealed that when OSIRIS-REx touched the asteroid it experienced the same resistance, very little, that a person would feel while squeezing the plunger of a French press coffee bottle. “When we fired our propellers to get off the surface, we were still submerged in the asteroid,” said Ron Ballouz, an OSIRIS-REx scientist based at the Johns Hopkins Laboratory of Applied Physics in Laurel, Maryland. .
Ballouz and the research team performed hundreds of computer simulations to deduce Bennu’s density and cohesion from spacecraft images and acceleration information. Engineers varied the surface cohesion properties in each simulation until they found the one that best fit their real-life data.
This vision of the asteroid Bennu expelling particles from its surface on January 19, 2019 was created by combining two images taken aboard NASA’s OSIRIS-REx spacecraft. Other image processing techniques were also applied, such as cropping and adjusting the brightness and contrast of each image. (Credits: NASA / Goddard / University of Arizona / Lockheed Martin)
Now, this accurate information about the surface of Bennu can help scientists better interpret remote observations of other asteroids, which could be useful for designing future asteroid missions and for developing methods to protect Earth from collisions with asteroids. asteroids.
It is possible that asteroids like Bennu, barely joined by gravity or electrostatic force, could break into the Earth’s atmosphere and therefore represent a different type of danger than solid asteroids. “I think we are still in the beginning of understanding what these bodies are, because they behave in a very counterintuitive way,” said Patrick Michel, a scientist at OSIRIS-REx and director of research at the Center National de la Recherche Scientifique in Côte d’Ivoire. ‘Azur Observatory in Nice, France.
References:
“Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu” by DS Lauretta, CD Adam, AJ Allen, R.-L. Ballouz, OS Barnouin, KJ Becker, T. Becker, CA Bennett, EB Bierhaus, BJ Bos, RD Burns, H. Campins, Y. Cho, PR Christensen, ECA Church, BE Clark, HC Connolly, MG Daly, DN DellaGiustina, CY Drouet d’Aubigny, JP Emery, HL Enos, S. Freund Kasper, JB Garvin, K. Getzandanner, DR Golish, VE Hamilton, CW Hergenrother, HH Kaplan, LP Keller, EJ Lessac-Chenen, AJ Liounis, H. Ma , LK McCarthy, BD Miller, MC Moreau, T. Morota, DS Nelson, JO Nolau, R. Olds, M. Pajola, JY Pelgrift, AT Polit, MA Ravine, DC Reuter, B. Rizk, B. Rozitis, AJ Ryan , EM Sahr, N. Sakatani, JA Seabrook, SH Selznick, MA Skeen, AA Simon, S. Sugita, KJ Walsh, MM Westermann, CWV Wolner and K. Yumoto, July 7, 2022, Science.DOI: 10.1126 / science .abm1018
by Kevin J. Walsh, Ronald-Louis Ballouz, Erica R. Jawin, Chrysa Avdellidou, Olivier S. Barnouin, Carina A. Bennett and Edward B. Ballouz, Bierhaus, Brent J. Bos, Saverio Cambioni, Harold C. Connolly, Marco Delbo, Daniella N. DellaGiustina, Joseph DeMartini, Joshua P. Emery, Dathon R. Golish, Patrick C. Haas, Carl W. Hergenrother, Huikang Ma, Patrick Michel, Michael C. Nolan, Ryan Olds, Benjamin Rozitis, Derek C Richardson , Bashar Rizk, Andrew J. Ryan, Paul Sanchez, Daniel J. Scheeres, Stephen R. Schwartz, Sanford H. Selznick, Yun Zhang, and Dante S. Lauretta, July 7, 2022, Science Advances.DOI: 10.1126 / sciadv. abm6229
NASA’s Goddard Space Flight Center offers global mission management, systems engineering, and mission security and assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the scientific team and the planning of scientific observation and mission data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and offers flight operations. 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 Directorate in Washington.