Skip to comments.Surprise – Again! NASA Spacecraft Reveals Asteroid Bennu Is Not What It Seemed
Posted on 07/08/2022 6:51:20 AM PDT by Red Badger
OSIRIS REx Spacecraft Leaving Bennu Surface
NASA’s OSIRIS-REx spacecraft leaving the surface of asteroid Bennu after collecting a sample. Credit: NASA’s Goddard Space Flight Center/CI Lab/SVS
Scientists have learned something astonishing after analyzing data gathered when NASA’s OSIRIS-REx spacecraft collected a sample from asteroid Bennu in October 2020. The spacecraft would have sunk into the asteroid had it not fired its thrusters to back away immediately after it grabbed its sample of dust and rock from Bennu’s surface.
“Our expectations about the asteroid’s surface were completely wrong.” — Dante Lauretta, principal investigator of OSIRIS-REx
Unexpectedly, it turns out that the particles making up Bennu’s exterior are so loosely packed and lightly bound to each other that if a person were to step onto the asteroid they would feel very little resistance. It would be like stepping into a pit of plastic balls that are popular play areas for kids.
“If Bennu was completely packed, that would imply nearly solid rock, but we found a lot of void space in the surface,” said Kevin Walsh, a member of the OSIRIS-REx science team from Southwest Research Institute, which is based in San Antonio.
NASA's OSIRIS REx Spacecraft Surface of Asteroid Bennu
Side-by-side images from NASA’s OSIRIS-REx spacecraft of the robotic arm as it descended towards the surface of asteroid Bennu (left) and as it tapped it to stir up dust and rock for sample collection (right). OSIRIS-REx touched down on Bennu at 6:08 pm EDT on October 20, 2020. Credit: NASA’s Goddard Space Flight Center
The latest findings about Bennu’s surface were published on July 7, 2022, in a pair of papers in the journals Science and Science Advances, led respectively by Dante Lauretta, principal investigator of OSIRIS-REx, based at University of Arizona, Tucson, and Kevin Walsh. These surprising results add to the intrigue that has gripped scientists throughout the OSIRIS-REx mission, as Bennu has proved consistently unpredictable.
The first surprise the asteroid presented was in December 2018, when NASA’s spacecraft arrived at Bennu. The OSIRIS-REx team found a rough surface littered with boulders instead of the smooth, sandy beach they had expected based on observations from Earth- and space-based telescopes. Reasearchers also discovered that Bennu was ejecting particles of rock from its surface into space.
“Our expectations about the asteroid’s surface were completely wrong,” said Lauretta.
The latest clue that Bennu was not what it seemed came after the OSIRIS-REx spacecraft picked up a sample and beamed stunning, close-up images of the asteroid’s surface to Earth. “What we saw was a huge wall of debris radiating out from the sample site,” Lauretta said. “We were like, ‘Holy cow!’”
VIDEO AT LINK.................
Near-Earth asteroid Bennu is a rubble pile of rocks and boulders left over from the formation of the solar system. On October 20, 2020, NASA’s OSIRIS-REx spacecraft briefly touched down on Bennu and collected a sample for return to Earth. During this event the spacecraft’s arm sank far deeper into the asteroid than expected, confirming that Bennu’s surface is loosely bound. Now, scientists have used data from OSIRIS-REx to revisit the sample-collection event and better understand how Bennu’s loose upper layers are held together. Credit: NASA’s Goddard Space Flight Center/CI Lab/SVS
Mission scientists were perplexed by the abundance of pebbles strewn about, given how gently the spacecraft tapped the surface. Even more bizarre was that the spacecraft left a big crater that was 26 feet (8 meters) wide. “Every time we tested the sample pickup 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 Bennu’s surface “to see how big of a mess we made,” Lauretta said.
Researchers analyzed the volume of debris visible in before and after images of the sample site, nicknamed “Nightingale.” They also looked at acceleration data collected during the spacecraft’s touch down. This data revealed that as OSIRIS-REx touched the asteroid it experienced the same amount of resistance – very little – a person would feel while squeezing the plunger on a French press coffee carafe. “By the time we fired our thrusters to leave the surface we were still plunging into the asteroid,” said Ron Ballouz, an OSIRIS-REx scientist based at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
Ballouz and the research team ran hundreds of computer simulations to deduce Bennu’s density and cohesion based on spacecraft images and acceleration information. Engineers varied the surface cohesion properties in each simulation until they found the one that most closely matched their real-life data.
Asteroid Bennu Particles
This view of asteroid Bennu ejecting particles from its surface on Jan. 19, 2019, was created by combining two images taken on board NASA’s OSIRIS-REx spacecraft. Other image processing techniques were also applied, such as cropping and adjusting the brightness and contrast of each image. (Credit: NASA/Goddard/University of Arizona/Lockheed Martin)
Now, this precise information about Bennu’s surface can help scientists better interpret remote observations of other asteroids, which could be useful in designing future asteroid missions and for developing methods to protect Earth from asteroid collisions.
It’s possible that asteroids like Bennu — barely held together by gravity or electrostatic force — could break apart in Earth’s atmosphere and thus pose a different type of hazard than solid asteroids. “I think we’re still at the beginning of understanding what these bodies are, because they behave in very counterintuitive ways,” said Patrick Michel, an OSIRIS-REx scientist and director of research at the Centre National de la Recherche Scientifique at Côte d’Azur Observatory in Nice, France.
“Spacecraft sample collection and subsurface excavation of asteroid (101955) Bennu” by D. S. Lauretta, C. D. Adam, A. J. Allen, R.-L. Ballouz, O. S. Barnouin, K. J. Becker, T. Becker, C. A. Bennett, E. B. Bierhaus, B. J. Bos, R. D. Burns, H. Campins, Y. Cho, P. R. Christensen, E. C. A. Church, B. E. Clark, H. C. Connolly, M. G. Daly, D. N. DellaGiustina, C. Y. Drouet d’Aubigny, J. P. Emery, H. L. Enos, S. Freund Kasper, J. B. Garvin, K. Getzandanner, D. R. Golish, V. E. Hamilton, C. W. Hergenrother, H. H. Kaplan, L. P. Keller, E. J. Lessac-Chenen, A. J. Liounis, H. Ma, L. K. McCarthy, B. D. Miller, M. C. Moreau, T. Morota, D. S. Nelson, J. O. Nolau, R. Olds, M. Pajola, J. Y. Pelgrift, A. T. Polit, M. A. Ravine, D. C. Reuter, B. Rizk, B. Rozitis, A. J. Ryan, E. M. Sahr, N. Sakatani, J. A. Seabrook, S. H. Selznick, M. A. Skeen, A. A. Simon, S. Sugita, K. J. Walsh, M. M. Westermann, C. W. V. Wolner and K. Yumoto, 7 July 2022, Science. DOI: 10.1126/science.abm1018
“Near-zero cohesion and loose packing of Bennu’s near-subsurface revealed by spacecraft contact” by Kevin J. Walsh, Ronald-Louis Ballouz, Erica R. Jawin, Chrysa Avdellidou, Olivier S. Barnouin, Carina A. Bennett, Edward B. 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 Sánchez, Daniel J. Scheeres, Stephen R. Schwartz, Sanford H. Selznick, Yun Zhang and Dante S. Lauretta, 7 July 2022, Science Advances. DOI: 10.1126/sciadv.abm6229
NASA’s Goddard Space Flight Center provides overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provides 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 Science Mission Directorate Washington.
This should be a cautionary tale for scientists everywhere. No matter how good you think your models are, reality trumps them every time.
This is solid evidence................no, wait.................
“The OSIRIS-REx team found a rough surface littered with boulders instead of the smooth, sandy beach they had expected based on observations from Earth- and space-based telescopes.”
But these same telescopes can accurately observe exoplanets and solar systems millions of light years from Earth. 😆
So drilling down 500 feet to plant the nuclear warhead would only require cans of compressed air?
Apparently so. The entire thing is held together by mutual attraction of their combined gravity wells..................
A hundred tons of solid rock hitting the atmosphere will scorch off a few tons on the way down, make a big sonic boom (think Chelyabinsk) thump into the ground and leave a smallish crater and local damage.
A hundred tons of gravel hitting the atmosphere will disintegrate and every single ounce of that hundred tons moving at tens of thousands of miles per hour will be exposed to static atmosphere at the same time, be frictionally super heated, flash from solid to white hot vapor. None of the solids will make it to the ground, but only as re-condensed pinheads of glassy rock. No crater.
On the other hand, the shock wave from all that energy released in a small space and time (think Tunguska) will flatten pretty much everything for 50 miles or more.
Of the thousands of exoplanets discovered so far, less than a dozen have been found using telescopes. The rest have relied upon other more indirect methods, and are typically hundreds or thousands of light years away, not millions.
As the asteroid approaches Earth, it will be pulled apart into a string of separate groups and individual rocks like the comet that struck Jupiter.
Hopefully they will mostly burn up as they enter the atmosphere........................
So Bennu is...fluffy?
Shoemaker-Levy broke up when it passed Jupiter, I don’t think there would be the same lateral Roche limit stresses on something coming straight in.
Bennu probably isn’t as compacted as the comet was. It’s barely conglomerated..................
So, if it’s constantly ejecting matter, how has it been doing it for “billions” of years? To be doing that, it would have had to start at the size of a small planet, which of course means it would not have been able to become the loose collection of debris it is today....
Inquiring minds want to know!
It’s too small to have sufficient gravity to hold everything tightly together.
It needs Gravitas!....................
Not left over from the birth of the Solar System. Left over from the destroyed planet that is now the Asteroid Belt. Google astronomer Tom Van Flandern.
Good article. Thanks for posting.
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