Astronomers have discovered how red stripes appeared on Ryugu asteroid

Japanese planetologists analyzed the images that the Hayabusa-2 probe received at the time of its landing on the surface of the asteroid Ryugu, and found hints that mysterious deposits of red rocks on its surface formed during its recent approach to the Sun. The findings of scientists published the scientific journal Science.

“Red rocks on the Ryugu asteroid could appear due to the fact that its orbit temporarily changed around 300 thousand years ago, as a result of which the asteroid became closer to the Sun. Its surface began to warm up more, causing the organic deposits on its surface to turn red “, – scientists write.

The Hayabusa-2 probe was launched in early December 2014 in order to study the asteroid Ryugu, as well as collect rock samples from its surface and deliver them to Earth.

The probe did this in two stages. First, he approached the surface of the asteroid in February 2019 and shot a five-gram tantalum bullet at it. Hitting the surface of the asteroid, it was supposed to pick up the dust that Hayabusa-2 had collected in the sampler.

 
Two months later, the probe dropped a bomb on Ryuga with about 4.5 kg of HMX, creating a man-made crater on the surface of the asteroid. In July last year, “Hayabusa-2” once again approached the surface of the asteroid at the point of explosion, taking allegedly pure samples of the primary matter of the solar system.

Blue red asteroid
However, the images that the camera took at the time of the first approach to the surface, made Japanese planetologists doubt it. In these photographs, samples of rocks are visible that a tantalum bullet threw up.


Image of Hayabusa-2 probe at the first approach to the surface of the Ryugu asteroid
© JAXA / U. Tokyo / Kochi U./Rikkyo U./Nagoya U./Chiba Inst. Tech./Meiji U./U. Aizu / aist

The fact is that immediately after the arrival of Hayabusa-2 to Ryug, scientists noticed that its surface is heterogeneous in composition. It is covered with alternating stripes of red and blue rocks, the nature of which until recently remained a mystery to astronomers.

At the point of the probe’s first approach to the surface of the asteroid, scientists note that blue rocks prevailed, which planetologists associated with the primary matter of the solar system. At the same time, scientists associated red rocks with less pristine matter, which fell into the bowels of the asteroid at the time of the death of its ancestor and the formation of Ryugu from its fragments.

When scientists began to examine the Hayabusa-2 landing and take-off shots, they found that a significant part of these red rocks looked like sand, which was easily blown off the probe’s engines from the Ryugu’s surface. Along with samples of blue primary matter, quite a lot of red rocks fell into the samplers of the apparatus.

A similar structure of the red regions of the asteroid, according to planetologists, suggests that they appeared on the surface of a celestial body relatively recently, about 300 thousand years ago. According to scientists, this happened as a result of the fact that Ryugu’s orbit changed sharply at that time, because of which it first fell to the Sun and became covered with a thin layer of red “sand”.

Blue stripes on the Ryugu surface, scientists note, arose much later, due to the fact that part of the red sand was ejected from the equatorial regions of the asteroid under the action of rotation force, as well as as a result of the formation of new craters in other parts of its surface. Studying the samples of red and blue matter that Hayabusa-2 will bring to Earth at the end of this year will help scientists test this hypothesis and finally learn the history of Ryugu formation.

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