Monday, April 24, 2023

3972 - BENNU ASTEROID - sample returns September, 2023.

 

-   3972 -  BENNU  ASTEROID  -  sample returns September, 2023.    The OSIRIS-REx mission unleashed an unexpected explosion when it touched down on asteroid Bennu in October 2020 to collect a precious sample to carry home to Earth.


-----------------  3972  - BENNU  ASTEROID  -  sample returns September, 2023.

-    Mission scientists have described the dramatic sample retrieval, which led to surprising discoveries about the asteroid's nature.    The findings might have implications for a possible future deflection mission, should the 1,640-feet-wide Bennu one of the riskiest known near-Earth asteroids ever threaten to impact the planet.

-

-    We expected the surface to be pretty rigid, like touching down on a gravel pile  A little bit of dust flying away and a few particles jumping up.  But, the images after the event showed a giant wall of debris flying away from the sample side.

-

-     Six months after sample collection, in April 2021, the researchers got another glimpse of the OSIRIS-REx touchdown site. When the spacecraft first arrived at Bennu, that site, called “Nightingale”, sat within a 65-foot-wide impact crater. After touchdown, mission scientists found a brand new 26-foot-wide gaping hole in the surface, with displaced rubble and boulders scattered around the site.

-

-    That's a surprisingly large scar; scientists had expected to scoop out a bit about as wide as the sample collector itself, 12 inches. "But, there clearly was no resistance whatsoever. The surface was soft and flowed away like a fluid.

-

-    The probe sank as deep as 30 inches, revealing pristine material that, unlike the asteroid's surface, was unaltered by the steady battering of cosmic rays and the solar wind, the streams of high-energy particles from the sun.

-

-    From the measurements acquired during this repeat visit, they calculated that the density of the surface material was only about 31 to 44 pounds per cubic foot.   For comparison, "a typical Earth rock" has a density about six times higher, more like 190 pounds per cubic foot per cubic meter.

-

-     A second study, based on measurements of forces exerted on the probe during the impact, confirmed those numbers.   The surface boulders are very porous and there is a lot of void space between them.We expected that small, fine grains and dust would stick to the large boulders and fill the void space and act as a glue to provide some strength, which would allow the surface to push back against the spacecraft more. But it's not there.

-

-    Bennu's soft, fluffy nature may complicate a possible future deflection attempt, should astronomers determine the rock threatens to hit Earth. At 1,640 feet wide, a strike by Bennu would cause continent-wide disruption on our planet. And even though NASA estimates the chance of collision at 1 in 2,700 between the years 2175 and 2199, Bennu is still one of the most dangerous asteroids currently known.

-

-    Moreover, scientists assume that many asteroids sport a similar "rubble pile" structure: essentially conglomerations of rock, gravel and dirt held together by weak gravitational forces. The sampling experiment at Bennu shows that it's almost impossible to predict how such a rubble pile might respond to an impact.

-

-   The touchdown did provide the first experience of really pressing something into the surface.   If we ever go and actually try to deflect something like this, we would need to know what the surface is like so that it doesn't just absorb the impact.

-

-   The underground material appeared more red compared to the bluish surface of Bennu, which suggests that cosmic rays and other forms of space weather erode the exposed space rocks. The reddish hues hint that organic molecules, like hydrocarbons, may be present inside the asteroid, which greatly interests researchers trying to understand the origins of life on Earth.

-

-    The scientists will have to wait until OSIRIS-REx's scheduled delivery in September 2023 to get their hands on the precious material. During the dramatic sampling attempt, the probe collected almost 9 ounces of asteroid dust, which is somewhat less than the teams had hoped for but still four times more than they need to conduct the analysis.

-

-   The OSIRIS-REx mission was recently extended and after the spacecraft drops off its cargo at Earth next year, it will head to Apophis, another high-risk asteroid, which it will visit in 2029.

-

                   April 24, 2023                 3972                                                                                                                          

----------------------------------------------------------------------------------------

-----  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Monday, April 24, 2023  ---------------------------

 

 

 

 

         

 

-

 

 

 

 

           

 

 

No comments:

Post a Comment