Shulou(Shulou.com)11/24 Report--

On the morning of November 4, Beijing time, it is reported that scientists have discovered the potential source of a special type of meteorite, whose characteristics may help explain some differences in the classification of near-Earth asteroids.

In 2013, a fireball exploded over Chelyabinsk, Russia, leaving behind a very rare meteorite that distinguishes it from other similar meteorites in its dark veins, a process known as shock darkening. However, planetary scientists have not been able to determine what type of asteroid these particular meteorites originated from.

Recently, researchers at the University of Arizona published a paper in the Journal of Planetary Science that an asteroid named 1998 OR2 has been discovered, which may be the source of impact darkening meteorites. The near-Earth asteroid, about 2.4 kilometers in diameter, passed the Earth at close range in April 2020. Meteorites are fragments of asteroids that collide with Earth.

Adam Battle, lead author of the study and a graduate student in planetary science at the University of Arizona, said: "shock darkening is a process of change. when an object has a large enough impact on planetary celestial bodies, the temperature will partially or completely melt planetary rocks, changing their appearance in human visual observations and data records. at present, impact darkening has been found in meteorite samples. But they only come from a small number of meteorite samples from the solar system's asteroid belt, which lies between Mars and Jupiter. "

Vishnu Reddy, a professor of planetary science and Barter's consultant, discovered the impact darkening of the asteroid belt between 2013 and 2014. He and engineering professor Roberto Farfaro (Roberto Furfaro) are in charge of the space domain consciousness laboratory of the lunar and planetary laboratory, where Balter is said to have worked since 2019.

The researchers found evidence of shock darkening in the meteorite. Reddy pointed out that meteorite collisions are common in asteroids and any solid matter in the solar system, because we can see the corresponding impact craters from spacecraft observation images. however, it is very rare to find meteorite source celestial bodies that produce collision melting and impact darkening effects, and finding a near-Earth asteroid dominated by this process is of great significance for collision risk assessment. Balter's results show that in our classification tools, ordinary chondrite asteroids may appear carbonaceous if they are affected by impact darkening, and the two materials have different physical strengths. this is important when trying to deflect a dangerous asteroid.

Balter, Reddy and colleagues used the Kuiper Space Science roof's RAPTORS telescope to collect data on the surface composition of a 1998 OR2 asteroid and determined that it looked like an ordinary chondrite asteroid. Chondrite asteroids are lighter in appearance and contain olivine and pyroxene minerals.

However, when the team analyzed the data through a classification tool, the results showed that the asteroid was a carbonaceous asteroid, a typical dark and relatively unfeatured asteroid.

"this mismatch was one of the potential early reasons for the project's investigation," Balter said. "this asteroid is not a mixture of ordinary chondrite and carbonaceous asteroid, depending on its mineral composition, it must be an ordinary chondrite asteroid, but it has been changed, most likely through the process of shock darkening, so it looks like a carbonaceous asteroid when observed by classification tools."

The hypothesis of shock darkening theory appeared as early as the 1980s, but it was not until scientists discovered that the fireball meteorites over Russia in 2013 had the characteristics of shock darkening that the theory received people's attention and in-depth study.

Scientists, including Reddy, became interested in shock darkening, and he soon discovered impact darkening asteroids in the asteroid belt. Balter said that of the more than 60,000 ordinary spherical meteorites found on Earth, about 2% of meteorites have experienced varying degrees of impact and collision.

Researchers can rule out many other potential factors. 1998 OR2 appears to be a carbonaceous asteroid rather than an ordinary chondrite asteroid, and one possible reason for the difference is space weathering, in which case exposure to space can cause changes in the asteroid's surface, making the asteroid's surface slightly redder than the original color. Shock darkening is a process that suppresses the appearance of olivine and pyroxene and darkens the surface of asteroids, making them look like carbonaceous asteroids.

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