The 'OSIRIS-REx' probe approaches the asteroid Bennu to collect samples and bring them to Earth

After a journey of four years (and two more ahead until it returns to Earth), the probe baptized with the pharaonic name of

approaches the remote asteroid Bennu around midnight, peninsular time, to collect a few grams of samples that can be traced back to the very origins of the Solar System.

NASA has a knack for naming its ships with increasingly sophisticated acronyms.

In this case,

stands for objectives:

rigins,

pectral

nterpretation,

esource

dentification,

ecurity-

egolith

plorer.

Bennu is an asteroid shaped like a diamond, measuring less than 500 meters in diameter and rotating on itself once every four hours.

So fast that pebbles at its equator are thrown from time to time by the centrifugal force itself and can go into orbit around it like tiny satellites.

Bennu's name was proposed by Michael Puzio, a nine-year-old boy who certainly demonstrated an amazing knowledge of Egyptian mythology.

It refers to a bird from Pharaonic Egypt, more or less equivalent to the Greek Phoenix.

In his opinion, the robotic arm with which he must collect a sample is reminiscent of the extended leg of a wader.

Accurate mapping

Bennu is surely the best mapped celestial body in all of history.

The probe's cameras have made it possible to explore its entire surface with a detail of less than 20 centimeters.

Approaching sometimes less than two kilometers.

The result is a three-dimensional map showing even fist-sized boulders.

And is that Bennu is little more than a pile of rubble sadly held by its own gravity.

At the poles, this is barely nine millionths of the Earth's force;

at the equator, due to its rapid rotation, three times less.

Under these conditions it is impossible to imagine that a probe could land on it and remain parked there.

And much less think about using a digging bucket to collect samples.

At the first contact with the ground, the mere touch would be enough to launch the vehicle back into space.

Difficult maneuver

For this reason,

use a pneumatic system with which to obtain perhaps a few tens of grams of dust: It will descend very slowly in an area almost free of rocks, extending in front a slim robotic arm with a bowl at its end.

At the moment of making contact with the ground, it will shoot a jet of nitrogen enough to lift a cloud of debris, some of which will be trapped in the container.

Something like a vacuum cleaner but in reverse: blowing instead of absorbing.

It is not certain that the procedure will work the first time.

The probe can get too close too fast;

or enter the wrong angle;

or simply go to lean on a rock that disperses the gas sideways without lifting enough material ... To try to guarantee success, the on-board cameras will monitor the descent, centimeter by centimeter, comparing the rocks on the ground with a map previously stored in the computer memory.

If there are deviations, it is possible to correct them to some extent.

And if, despite everything, the first attempt fails, you have enough nitrogen reserves to try three times.

Unaltered material

What is the interest of studying such mountains of space debris that probably do not even have the consistency of a massive body?

Essentially, because that is a pristine material, representative of what the Solar System was like during its formation, long before the Earth itself existed.

No remote analysis, not even the analysis of meteorites that fall on our planet, can compare with the opportunities offered by holding a piece of material that has remained unchanged for eons.

It is not the first time that an asteroid has been visited or that samples have been obtained.

The first corresponded to a Japanese probe called

, which ten years ago managed to return with a few grams of dust collected from the asteroid Itokawa.

It was a true odyssey in which the technicians had to fight against myriad problems, including communication failures, navigation errors and even freezing of fuel in the supply lines.

Now, the second

has repeated the exploration, this time on another asteroid known as Ryugu, about twice as long as Bennu.

He is on his way back to Earth, where by the end of the year he will have to drop a capsule with the samples collected there.

The return of

must wait until September 2023.

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