- 3802 - ASTEROID
BENNU visit in 2020? When
OSIRIS-REx touched down on asteroid Bennu in October 2020 to collect a precious
sample to carry home to Earth it unleashed an unexpected explosion.
--------- 3802
- ASTEROID BENNU visit in 2020?
-
- Mission scientists say that 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,
kind of like if you touch down on a gravel pile: a little bit of dust flying
away and a few particles jumping up. Instead they saw 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.
-
- The spacecraft sunk in because 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.
-
- 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.
-
- 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 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.
-
- 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.
-
January 1,
2022 ASTEROID BENNU visit in 2020? 3899
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