One was more red, while the other was more blue. Now, based on a new analysis of the observations captured by the spacecraft, scientists know why.
Ryugu, like Icarus in Greek mythology, at a certain point in his history went a little too close to the sun.
Hayabusa2 landed on Ryugu on February 21, 2019, to collect a sample that is currently en route to Earth and will return in December 2020 after leaving the asteroid in December 2019. This touchdown also allowed the spacecraft camera to observe in detail the surface of the asteroid.
This landing event also caused a splash of material to be sent to the spacecraft’s thrusters. It disturbed a coating of dark fine-grained material on the asteroid similar to the reddish materials on the surface of the asteroid. This was compared to the location of the asteroid craters.
And that’s when Tomokatsu Morota, author of the study and associate professor at the University of Tokyo, and his colleagues determined “that the red and dark grains raised by the thrusters immediately after the touchdown were produced by solar heating,” said Morota in an email to CNN.
“We also found that surface alteration by solar heating occurred in a short period of time based on the stratigraphic relationship between the identified craters and the redder material. These results suggest that Ryugu has undergone an orbital excursion. near the sun. “
Asteroids don’t just go rogue and head for the sun. Their movements are governed by the orbits of the planets.
“In general, near-Earth asteroids are thought to be transported from the main asteroid belt to near-Earth orbits by orbital resonance with Jupiter and Saturn,” said Morota. “We think Ryugu underwent an orbital excursion near the sun when Ryugu was transported from the main belt to an orbit near Earth.”
This could have happened even when Ryugu became a near-Earth asteroid, said Patrick Michel, co-author of the study and director of research at the French National Center for Scientific Research in Paris.
“When an asteroid becomes close to Earth, close encounters with the planets disrupt their trajectory and experience a sort of casual walk in their medium distance from the sun,” Michel wrote in an email to CNN. “In Ryugu’s case, the planetary perturbations were such as to bring it closer to the sun at some point, and therefore to its current orbit.”
Michel added that asteroids do not undergo a typical evolution. Their unique trajectories are controlled by the planets.
Fortunately, the specimen that is returned to Earth contains a mix of materials from the asteroid’s surface – including evidence of the asteroid’s excursion to the sun.
The example may contain clues to Ryugu’s history, which are otherwise difficult to understand.
“Unfortunately, there is no way to trace the evolution of this asteroid by starting the calculations from its current orbit and calculating it back in time,” said Michel. “This is not possible for asteroids like Ryugu that have a very chaotic evolution because of its close approaches to the planets.”
This will help scientists not only better understand Ryugu, but also other aspects of the history of our solar system.
“The way these molecules chemically change from solar heating is important for understanding the chemical evolution of organic molecules, which may have been transported to primordial Earth,” said Morota.
Since visiting Ryugu, Hayabusa2 has returned a wide range of data that scientists have been able to study and analyze before the samples return to Earth.
Ryugu is a dark spinning top shaped asteroid measuring approximately 3000 feet in width. The surface is covered with boulders. It is also incredibly dry.
The photos captured by the spacecraft revealed a uniform distribution of dark and rough rocks, in addition to those that are bright and smooth. Scientists believe there are two types of material on the asteroid because it probably formed from the remaining rubble after its parent body was hit.
The rocks are similar to carbonaceous chondrites, which are primitive meteorites. Some rocks contain small colored materials called inclusions which may contain minerals such as olivine. This is also found in carbonaceous chondrites.
The researchers also determined that the asteroid is largely made up of highly porous material. This may explain why carbon-rich meteorites are rarely found on Earth; our atmosphere protects them and breaks them into fragments.
Information such as this, obtained by sending a spacecraft to the asteroid, will be compared with data collected by NASA’s OSIRIS-REx mission by visiting another near-Earth carbonaceous asteroid called Bennu.
“All the knowledge we are acquiring with Hayabusa2 has not been obtained from terrestrial observations,” said Michel. “So the detailed characterization of an asteroid definitely needs these space adventures!”
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