More results about Bennu from OSIRIS-REx
Scientists using the OSIRIS-REx spacecraft have now published a special collection of papers outlining some of their discoveries made during that spacecraft’s observations of the asteroid Bennu from February to October 2019.
These papers just make official much of what was revealed during a conference I attended in November 2019. To sum up the papers:
- Bennu has a lot of carbonates across its surface.
- Some of that material came from another object that had to have had water.
- The asteroid’s boulders come in two types, dark-porous and bright-solid, with the latter likely from that water-bearing other asteroid
- Bennu’s surface is fresh, only recently exposed to space, including the sample site Nightingale.
- Bennu’s interior has large voids, and its equatorial region is less dense.
The discovery of carbonates, produced from the interaction of water and carbon dioxide, is a big deal. As Dante Lauretta, OSIRIS-REx principal investigator, explained at that November conference, “To me this is one of the most exciting results from the conference.”
These findings have allowed scientists to theorize that Bennu’s parent asteroid likely had an extensive hydrothermal system, where water interacted with and altered the rock on Bennu’s parent body. Although the parent body was destroyed long ago, we’re seeing evidence of what that watery asteroid once looked like here – in its remaining fragments that make up Bennu. Some of these carbonate veins in Bennu’s boulders measure up to a few feet long and several inches thick, validating that an asteroid-scale hydrothermal system of water was present on Bennu’s parent body.
The material could not have been created on Bennu itself, which means it formed on a different object that was large enough and existed long enough to create the veins in these boulders. That material was then flung back into space to settle onto Bennu’s surface.
The freshness of Bennu’s surface is also a big deal, as it means that etither the asteroid is not that old, or that its surface somehow gets plowed over periodically. It also means that when OSIRIS-REx grabs samples at the Nightingale site on October 20th, they will be grabbing material that has not been altered much by the harsh environment of space.
Finally, the data about Bennu’s interior and density is maybe the neatest discovery. As the press release notes,
The reconstructed gravity field shows that the interior of Bennu is not uniform. Instead, there are pockets of higher and lower density material inside the asteroid. It’s as if there is a void at its center, within which you could fit a couple of football fields. In addition, the bulge at Bennu’s equator is under-dense, suggesting that Bennu’s rotation is lofting this material.
Bennu’s very weak gravity makes it a very alien and hard-to-comprehend place. It appears that the gravel in this floating gravel pile is barely held together, some interlocking in a way that leaves many open gaps, with other pieces pulled outward by the spin of the asteroid.
In reading these results, my first impression was an overwhelming sense of time and its inconceivable vastness. Much of Bennu’s most primitive material comes from the early solar system, about six billion years ago. Other material is newer, but required many many millions of years to get created elsewhere, and then somehow end up in space to be captured by this asteroid.
A million years is a very long time. A billion years is a thousand times longer. To conceive such time frames and all that can happen during that time is practically impossible. Bennu has shown us just a hint of how much can happen, some of which we would never have imagined otherwise.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Scientists using the OSIRIS-REx spacecraft have now published a special collection of papers outlining some of their discoveries made during that spacecraft’s observations of the asteroid Bennu from February to October 2019.
These papers just make official much of what was revealed during a conference I attended in November 2019. To sum up the papers:
- Bennu has a lot of carbonates across its surface.
- Some of that material came from another object that had to have had water.
- The asteroid’s boulders come in two types, dark-porous and bright-solid, with the latter likely from that water-bearing other asteroid
- Bennu’s surface is fresh, only recently exposed to space, including the sample site Nightingale.
- Bennu’s interior has large voids, and its equatorial region is less dense.
The discovery of carbonates, produced from the interaction of water and carbon dioxide, is a big deal. As Dante Lauretta, OSIRIS-REx principal investigator, explained at that November conference, “To me this is one of the most exciting results from the conference.”
These findings have allowed scientists to theorize that Bennu’s parent asteroid likely had an extensive hydrothermal system, where water interacted with and altered the rock on Bennu’s parent body. Although the parent body was destroyed long ago, we’re seeing evidence of what that watery asteroid once looked like here – in its remaining fragments that make up Bennu. Some of these carbonate veins in Bennu’s boulders measure up to a few feet long and several inches thick, validating that an asteroid-scale hydrothermal system of water was present on Bennu’s parent body.
The material could not have been created on Bennu itself, which means it formed on a different object that was large enough and existed long enough to create the veins in these boulders. That material was then flung back into space to settle onto Bennu’s surface.
The freshness of Bennu’s surface is also a big deal, as it means that etither the asteroid is not that old, or that its surface somehow gets plowed over periodically. It also means that when OSIRIS-REx grabs samples at the Nightingale site on October 20th, they will be grabbing material that has not been altered much by the harsh environment of space.
Finally, the data about Bennu’s interior and density is maybe the neatest discovery. As the press release notes,
The reconstructed gravity field shows that the interior of Bennu is not uniform. Instead, there are pockets of higher and lower density material inside the asteroid. It’s as if there is a void at its center, within which you could fit a couple of football fields. In addition, the bulge at Bennu’s equator is under-dense, suggesting that Bennu’s rotation is lofting this material.
Bennu’s very weak gravity makes it a very alien and hard-to-comprehend place. It appears that the gravel in this floating gravel pile is barely held together, some interlocking in a way that leaves many open gaps, with other pieces pulled outward by the spin of the asteroid.
In reading these results, my first impression was an overwhelming sense of time and its inconceivable vastness. Much of Bennu’s most primitive material comes from the early solar system, about six billion years ago. Other material is newer, but required many many millions of years to get created elsewhere, and then somehow end up in space to be captured by this asteroid.
A million years is a very long time. A billion years is a thousand times longer. To conceive such time frames and all that can happen during that time is practically impossible. Bennu has shown us just a hint of how much can happen, some of which we would never have imagined otherwise.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Yes, a billion years is a VERY long time. This is a prime reason we need to be careful evaluating and interpreting the geology of alien bodies. Even very slow and subtle processes can have a dramatic effect on such time scales. which are simply beyond human experience
I’m not sure I can handle knowing that bits of planets make up asteroids. It’s supposed to be the other way around.