It wasn’t long before NASA’s OSIRIS-REx probe arrived at Earth, bringing back a sample of the asteroid Bennu. The spacecraft is expected to land on Sunday (24), around 12:30 pm (Brasilia time), after a long mission that lasted more than seven years and changed the way scientists view space rocks.
OSIRIS-REx was the third mission in history to collect a sample from an asteroid. The probe demonstrated the most comprehensive array of instruments ever flown on a space rock research mission. The spacecraft’s period of scanning Bennu’s surface and its brief descent to collect material showed scientists how little they knew about these objects.
Until the launch of this probe in 2016, two other missions had studied asteroids in detail. The most recent was Japan’s Hayabusa 1 spacecraft, which transported grains of sand and dust from the asteroid Itokawa to Earth in 2010. Previously, NASA’s NEAR-Shoemaker spacecraft explored the asteroid Eros in the late 1990s, landing on its surface in 2001 (but without returning samples, as She did not recover her energy after a period of hibernation, “sleeping” forever “in the arms” of Eros.
It was the Hayabusa 1 mission that first confirmed what scientists had long assumed: that many asteroids are not solid masses of rock, but rather agglomerations of rock, sand and gravel that arose from collisions between larger bodies throughout Earth’s history. planet solar system. These clumps, held together only by the weak gravitational forces of the rocks, became known as moraine piles.
In turn, OSIRIS-REx has brought revolutionary information, and there is still much to come after the samples are unpacked and analyzed. Learn about some of the mission’s discoveries:
The asteroid’s “debris piles” are not all the same
Until the OSIRIS-REx probe arrived at Bennu, scientists knew that the 492-meter rock had a different chemical composition than the one on the asteroid Itokawa. While this mineral is mostly made of a silica-rich material similar to quartz, Bennu is rich in carbon.
However, it is a rare example of a carbon-rich asteroid, called a B-type, which is thought to contain chemical compounds from the early times of the solar system.
The way the surface reflects light suggests that Bennu, like Itokawa, will be made of clumps of rock interspersed with large sand-filled craters, into which the spacecraft could land comfortably.
But according to the site Space.com websiteWhen OSIRIS-REx took its first close-up look at Bennu, it saw a “hellscape” of rocks rising against the small asteroid’s weak gravity to unexpected heights.
The rocks were strangely porous, which confounded telescope measurements and convinced astronomers that Bennu was sandy like Itokawa. The material from which these rocks were made was somewhat similar to clay that can be found on Earth, but the asteroid’s weak gravity allowed the rocks to form unexpected formations.
A study published in 2022 in the journal Natural earth sciences It has been suggested that the spongy nature of these rocks protects the irregular asteroid from impacts from other bodies.
Like a swamp
The reaction of the asteroid Bennu to the spacecraft’s landing was surprising. At first, the probe sank about 50 centimeters into the surface, as if it had been swallowed by a swamp. She was saved by the force of her rear thrusts.
However, activation of the thrusters sent a cloud of debris and dust into space, threatening the spacecraft as it retreated. Fortunately, OSIRIS-REx also survived this incident. Although relieved, the scientists were fascinated. According to expectations, the surface was supposed to be completely resistant to the weight of the spacecraft, like a pile of gravel.
Researchers are still searching for an explanation. It is believed that the low density may mean the presence of empty spaces between rocks in the asteroid’s surface layer. In the past, these gaps may have been filled with granular material, but over the billions of years that Bennu traveled through the solar system, these grains may have passed through the rocks and into the asteroid’s interior, which may, as a result, be much denser than the surface.
Surely scientists should be able to cut through the asteroid. Although this is not yet possible, they instead hope to gain some information about the interiors of cumulus asteroids through the European Space Agency’s Hera mission, which will study the consequences of the experimental impact of NASA’s DART spacecraft on the asteroid Demorphos, which It happened in 2016. September 2022.
These were just a few examples of how the OSIRIS-REx mission teaches about asteroids. Now, we can only wait for the successful return to Earth on Sunday and the completion of analyzes of the materials that the spacecraft is carrying with it. And it does not stop: later, it returns to space towards another asteroid: Apophis, which is expected to pass near Earth in 2029.
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