The black stuff reminds me of what Arthur Clarke wrote
about in his book "2061: Odyssey Three" when Heywood Floyd
get to land on Halley's Comet.
Asteroid Ryugu contains material older than the planets, among the most
primitive ever studied on Earth
By Keith Cooper published 1 day ago
Samples returned to Earth by a Japanese asteroid mission are the most
untouched materials ever studied in the solar system.
An artist's depiction of the Hayabusa2 spacecraft at the asteroid Ryugu.
(Image credit: NASA)
The asteroid Ryugu contains some of the most primitive material ever
studied in a laboratory on Earth, dating back to just 5 million years
after the formation of the solar system, according to an analysis of
samples retrieved by Japan's Hayabusa2 mission.
Because it is so old, it is made of the same stuff that formed the
planets. "Ryugu is one of the building blocks of Earth," team-member
Hisayoshi Yurimoto, a professor at Hokkaido University in Japan, told
The Japan Aerospace Exploration Agency's Hayabusa2 spacecraft launched
in December 2014 and arrived at asteroid Ryugu in 2019. It retrieved two
small samples of regolith, amounting to 5.4 grams, from the asteroid.
These samples then landed on Earth in a capsule equipped with a
parachute in December 2020.
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Upon their return, the samples were distributed among scientific groups,
including one team led by Tetsuya Yokoyama, a professor at the Tokyo
Institute of Technology. The team's newly published results suggest that
the composition of the samples is the closest match to the solar nebula
— the gas cloud that condensed to form the sun and planets — ever found.
As such, it is made up of the ingredients that formed the solar system
4.5 billion years ago.
The findings support previous research that also concluded that Ryugu
was made of primitive material, but until now it wasn’t known just how
old it was.
Ryugu is a carbonaceous chondrite, meaning it is made from carbon-rich
stony material. But remote observations by Hayabusa2 found some
unexplained discrepancies — including a darker surface color, a larger
abundance of phyllosilicate materials and a more porous composition than
expected — so laboratory analysis was required to better understand the
asteroid's true nature. Ryugu is somewhat similar to the Ivuna
meteorite, which fell in Tanzania in 1938 and was loaned by the Natural
History Museum in London to Yokoyama's team for their study.
"The comparison between Ivuna and Ryugu is very helpful for revealing
the characteristics of Ryugu," Yurimoto said.
Utilizing a range of techniques — including electron microscopy, X-ray
fluorescence, inductively coupled plasma mass spectrometry and thermal
ionization — the team found that the samples had formed within liquid
water, at a temperature of about 81 to 117 degrees Fahrenheit (27 to 47
degrees Celsius), roughly 5 million years after the solar system began
JAXA personnel inspect Hayabusa2's return capsule against the red soil
of the Woomera Prohibited Area in Australia on Dec. 5.
With a diameter of just 3,000 feet (900 meters), Ryugu is too small to
have generated enough heat to melt water ice. Therefore, Ryugu itself
must have originated from a larger parent body that formed just 2
million to 4 million years after the birth of the solar system. At some
point after 5 million years, a powerful impact with another asteroid
smashed Ryugu's parent body apart, with some of the fragments forming
Ryugu. This idea is supported by the presence of large boulders on
Ryugu's surface, which appear to have originated as debris from a giant
Ryugu's material can be dated thanks to the abundance of certain
elements — hydrogen and noble gases — within the samples. They are the
closest match that we have for the composition of the sun's visible
surface, the photosphere, which is used as a proxy for the composition
of the solar nebula.
No meteoritic or asteroidal material studied in a laboratory on Earth
has ever been found to be so primitive and pristine. Some meteorites,
like Ivuna, may have once been as pristine. But after lying on Earth for
decades, if not centuries — where they were exposed to atmospheric
moisture and weathering, and then handled by humans — their mineralogies
and elemental composition may have been compromised.
One key question that needs to be answered to fully explain the origin
of the planets is where minor bodies, such as asteroids and comets, some
of which became planetary building blocks, formed. Their compositions
suggest that many of these bodies did not form in their current orbits
and that in the chaotic early solar system, with its turbulent
protoplanetary disk and migrating planets, the minor bodies were pushed
around and moved away from where they formed.
By knowing when Ryugu's parent body formed, and that it contained water,
can we say where the asteroid must have formed?
— Asteroid Ryugu samples, now on Earth, reveal inner workings of the
— Watch Japan's Hayabusa2 land on asteroid Ryugu in this exciting video
— Strange bright rocks reveal glimpse of asteroid Ryugu's violent past
"This is a very difficult question," Yurimoto said. "We have no
quantitative answer, but it would be beyond the snow line of the solar
system, [which is] located at the orbit of Jupiter." (The snow line is
the distance from the sun where water ice could have condensed during
the formation of the solar system.)
This is only the beginning of the analysis of the samples brought home
by Hayabusa2. The next step is to use the information contained within
those samples to determine the abundances of various elements and their
isotopes in the early solar system when the planets were forming.
According to Yurimoto, once determined, those abundances "would become a
new standard for studies of the solar system."
The findings are published in the June 9 issue of the journal Science.
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