The asteroid (101955) Bennu was discovered by the Lincoln Near-Earth Asteroids Research team on September 11, 1999 from the Socorro Experimental Test Observatory (New Mexico). When it was chosen as the destination for a space mission by NASA’s OSIRIS-REx probe , the Planetary Society organized a contest to name it. The winner was a nine-year-old boy who suggested the name Bennu, which is a bird associated with the Egyptian god Osiris . Finally, after more than two years of travel (OSIRIS-REx was launched into space on September 8, 2016), on December 3, 2018 the NASA probe reached Bennu to observe it closely and take samples of its surface. , which will bring you back to Earth.
The data that the mission has collected so far in its first observations have yielded some results that have surprised scientists. Especially his age, which is much older than they imagined . According to their calculations, Bennu is between 100 million and 1 billion years old . NASA experts think it likely originated in the Main Asteroid Belt , a region located between the orbits of Mars and Jupiter. For astrophysicists, asteroids and comets are a valuable source of information for understanding the evolution of the nearby universe, since they are nothing more than remnants of the Solar System formation process .
Another fact that has surprised NASA thanks to what the instruments carried by the OSIRIS-REx probe have detected is the generalized presence of hydrated minerals in the asteroid’s soil , where large rocks abound.
There are more than 200 with a diameter greater than 10 meters. The varied and heterogeneous appearance of the Bennu surface, the absence of small craters and other features that indicate signs of recent activity seem to indicate that regions formed at different times coexist in this cosmic body. The asteroid is about 490 meters in diameter and is classified as PHA or potentially dangerous. Its orbit takes it closer to Earth more or less every six years, to be at a distance of about 450,000 kilometers (the Moon, for example, is 300,000 km from us).
From what is known so far about the evolution of its orbit, astronomers predict that Bennu will approach almost the distance of the Moon in the year 2135 . This approach is very likely to cause it to change its trajectory due to the force of Earth’s gravity.
Within the international team of the OSIRIS mission there are researchers from the Instituto de Astrofísica de Canarias (IAC), dedicated specifically to image processing and analyzing the photographs captured by the MapCam camera on board the ship. From what they have been able to measure so far, they know that the surface of the asteroid is quite dark , reflecting only 4.5% of sunlight. They have also detected that the colors of the asteroid are spectral type B, which is usually an indication of the presence of CM carbonaceous chondrites, where organic matter usually appears . Carbonaceous chondrites are the earliest known meteorites and contain primitive substances from the early Solar System. This indicates that asteroids like Bennu were able to bring hydrated, carbon-rich material to our planet.
Image credit: NASA / Goddard / University of Arizona.
