After orbiting it for almost two years, the spacecraft OSIRIS-REx NASA achieved land successfully this Tuesday on the asteroid Bennu, and extended his robotic arm to collect samples of its surface, a material that has not changed since its origin, about 4 billion years, and which is expected to reach Earth in 2023. It is the first time that the US space agency has managed to make one of its probes touch down on an asteroid.

After landing on Bennu, located more than 320 million kilometers from Earth, the OSIRIS-REx spewed compressed nitrogen onto the asteroid’s surface to lift up dust and gravel that would be collected by the probe. In an extremely dangerous maneuver called “Touch and Go” (tap and go), the spacecraft deployed a 3.35 meter long mechanical arm with a sort of ‘vacuum cleaner’ at its end, and collected samples for a few ten seconds, avoiding contact with stones that could damage it. Once successful, the probe, about the size of a pickup truck, backed off to a safe distance.

The ship took off from Cape Canaveral on September 8, 2016, arrived at the asteroid at the end of 2018 and, since then, has been orbiting it and conducting various studies on its composition, structure and activity.

During this time, OSIRIS-REx observed frequent particle ejection events until detecting the presence of very bright rocks, basaltic-type silicates, which contrast with the darkness of the rest of the material and suggest that come from outside, not from the original composition of the asteroid.

NASA will not know until the next few days if the collection has been successful and the sample is enough (about 60 grams) to return the probe to Earth or, otherwise, make a second try next January.

“An incredible feat”

“This has been an incredible feat,” its associate administrator for the Science Mission Directorate, Thomas Zurbuchen, said in a NASA statement.

“A piece,” he added, “of primordial rock that has been witness to all the history of our solar system you may now be ready to go home to generations of scientific discoveries, and we can’t wait to see what comes next. “

NASA highlighted in its statement that the asteroid Bennu “offers scientists a window to the early solar system, as it first began to take shape billions of years ago and spews out ingredients that could have helped sow life on Earth. “

If the mission has been successful, in March 2021 – the next time Bennu aligns itself with Earth properly – OSIRIS-REx will make its return.

What will the samples explain?

Like other asteroids of its kind, Bennu is rich in hydrated minerals and complex organic molecules, so studying this material, as found on the asteroid, can provide the keys to understanding how these compounds got to the young Earth and how they gave rise to the living beings that inhabit it today.

Rocks in Bennu.
NASA

The maneuver carried out by OSIRIS-REx was dangerous because, according to Julia de León, from the Canary Islands Institute of Astrophysics (IAC), “science has not got it right once again”, and what looked like a surface covered with fine dust from Earth turned out to be completely full of rocks, with dimensions ranging from a few centimeters to tens of meters. “It’s crazy. This made us change the strategy of choosing the place where the ship should maneuver for its safety,” he explained.

A 100.000 km/h

“We have arrived, we have studied it and now it is the most difficult thing: to get hold of a little Bennu to bring to Earth and study it,” said Javier Licandro, from the IAC.

Achieving it was, in fact, an enormous difficulty: lThe ship had to descend towards an object barely 500 meters that moves at 100,000 kilometers per hour, practically without gravity and with a surface covered with stones.

The objective of OSIRIS-REx was, specifically, to take a sample of the material that is inside a crater of 140 meters in diameter called Nightingale. This is in a region of only 16 meters in diameter, where there are far fewer stones than in the rest of the surface, and the abundance of dust seems to be sufficient.

Now, OSIRIS-REx will continue to orbit Bennu and will set out on its way back in 2021, toting “its invaluable cargo” in a sealed, vacuum-packed device, slated to fall somewhere in the world. Utah desert (EE UU) in 2023.