Asteroid Ryugu begins to tell his long story


The asteroid Ryugu, escorted by the Japanese spacecraft Hayabusa2, begins to reveal its secrets: hydrated minerals are present everywhere on its surface, according to researchers who hope to understand how asteroids could contribute to the presence of water on Earth and the emergence of life.

Three studies, published Tuesday in the journal Science, are devoted to this distant asteroid, an aggregate of rocks discovered in 1999.

"This is the first data available on a carbon asteroid," with those on the Bennu asteroid, studied by the American Osiris-Rex mission and published the same day in Nature, astrophysicist Patrick told AFP. Michel.

"We have discovered a new world, we feel a bit like Christopher Columbus," adds CNRS research director at the Côte d'Azur Observatory, which is one of the scientists at the Hayabusa mission.

Located 400 million miles from Earth, Ryugu, which is 900 meters in diameter, is a very old asteroid whose age is estimated to be between 100 million and a billion years from now. He has been escorted since June 2018 by the investigation of Japanese space agency Jaxa.

"Hydrated minerals are ubiquitous" on the surface, says AFP Kohei Kitazato of Aizu University in Fukushima.

"Carbon asteroids are considered as one of the potential sources of water on Earth. We hope that our results and the future analysis of the samples will provide us with new clues about the origin of the water," he says.

Hydrated minerals are rocks that have been in contact with water, but are no longer in the liquid state, at least on the surface, says Patrick Michel. "Inside, we do not know why the temperature drops dramatically just inches from the surface."

The astrophysicist points out that Ryugu is "less hydrated than Bennu." "It could mean that Ryugu may have warmed up a bit more than Bennu and may have been partially dehydrated."

Astrophysicists were surprised by the similarities between Ryugu and Bennu, including its shape, density and abundance of rocks on its surface.

Like Bennu, Ryugu is shaped like a sphere with a bubble at the equator. Turning in at 7.7 hours, it looks a bit "top", according to Patrick Michel.

Twice larger than Bennu, it has low density (1.2 grams per cm3) and is very porous.

Like Bennu, it is very dark, meaning it is potentially rich in carbon and therefore in organic compounds. But to verify this, it will be necessary to wait for the return on Earth, predicted for 2020, samples taken in the asteroid.

"We hope to bring back organic matter to see if its properties are compatible with those that have emerged in life on Earth," says the astrophysicist.

Researchers were surprised to find rocks almost across the surface.

Ryugu formed in the asteroid belt and "there is probably a cluster of small fragments of a larger body that was destroyed by a collision," Patrick Michel notes. "It is important to understand the history of these objects."

Hayabusa2 is scheduled to perform on April 5 an experiment that will send a projectile to the surface of Ryugu to create a crater, with the idea of ​​retrieving a sample later. "It's going to be great," enthuses the Frenchman.


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