As planned according to NASA’s careful calculations, the OSIRIS-REx spacecraft capsule landed in a military restricted area in the Utah desert at 4:52 p.m. (Spanish Peninsula Time). On board it carries a sample of around a quarter of a kilo of material that was collected two and a half years ago on the asteroid Bennu, a 500-meter-large rock whose shape is reminiscent of a diamond and which orbits between Earth and Mars.
The approximately 80 centimeter large capsule separated from the main ship four hours and one hundred thousand kilometers before landing and re-entered the atmosphere like a meteorite, reaching speeds of more than 40,000 kilometers per hour and generating temperatures of almost 3,000 degrees on its surface. It had no GPS or beacon on board, so its descent and position were tracked using radar and automatic video cameras.
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The sample container is airtight and will remain so until it reaches NASA’s Space Center in Houston. This is the only way to protect it from contamination by air gases. It will only be opened in an inert atmosphere, as part of a preliminary study process that will take about six months to catalog all its contents piece by piece. Small samples (25% of the total) will then be distributed to a team of 200 researchers who have been waiting for this moment for seven years since the probe was launched in 2016. The rest will remain in reserve, waiting for new techniques to be developed. and that other scientists – not yet born – are interested in analyzing it.
Several characteristics influenced the choice of Bennu. On the one hand, it is rich in carbon, suggesting that it may contain traces of amino acids, precursor molecules of life. On the other hand, it could pose a danger since its trajectory could bring it very close to Earth, possibly at a distance comparable to the distance flown by Meteosat, which will happen well into the 22nd century. Any change in its orbit could result in an impact, a very unlikely but not impossible event. These years of studies have allowed us to better understand its size and physical properties to develop a possible planetary defense mechanism, like the one tested a year ago by changing the orbit of the small dimorphic asteroid.
Address Apophis
Twenty minutes after the capsule detachment, the rest of the OSIRIS-REx spacecraft turned on its engines to align its orbit with another target, the asteroid Apophis. Where it is scheduled to arrive in 2029, exactly when it is closest to us. Since you have already used the reentry capsule, the sampling maneuver is eliminated and you are limited to examining its properties from a distance. In keeping with this new mission, the name was changed. From now on it is OSIRIS-APEX, from “APophis EXplorer”.
With this return to Earth, we now have samples from six extraterrestrial origins: the Moon, from which Americans, Russians and Chinese have accumulated more than 350 kilos; quarter kilo of the asteroids Itokawa, Ryugu and now Bennu; Milligram tail of comet Wild 2; and microscopic traces of solar wind.
Illustration of the OSIRIS-REx.AP spacecraft created by NASA
For completeness, we could also add small amounts of Mars and an asteroid like Vesta. No ship went there to pick them up; They literally fell from the sky for us. Millions of years ago, these bodies suffered an impact so violent that parts of their crust were ejected into space. After traveling around the sun for an eternity, some fell to Earth in the form of a meteorite. They are of course very rare and highly valued.
Except for the moon, all the bodies we have visited with robots are very small. Contrary to what it may seem, the low gravity makes the operation difficult. Entering an asteroid’s orbit is very complicated and requires extremely complicated calculations. We don’t even talk about landing anymore: only the NEAR Shoemaker ship managed to land on Eros almost a quarter of a century ago; Although this was more than just a landing, it was a slow-motion fall.
Japan was a pioneer
The Japanese space agency was the first to receive a sample of an asteroid, 25143 Itokawa, described as a “mountain of debris” barely held together by its weak gravity. So much so that it was impossible to land there and anchor firmly enough to scratch a sample. The Hayabusa probe slowly descended until a funnel at its base touched the ground. At that moment he fired a few metal projectiles, with the idea of stirring up a cloud of waste and sending at least some of it into the collection chamber.
The mission was full of unknowns from the start. The funnel landed at an angle and the technicians weren’t sure if it could catch anything. The maneuver resulted in a leak in a fluid line that would jeopardize the entire return journey. Halfway through, the ship began to wobble, lose its bearings on the sun, fuel froze in its tubes, and three of its four ion engines failed. After five years of effort and improvised solutions, his capsule landed in an Australian desert. Inside 1,500 microscopic regolith grains.
Image of the asteroid Ryugu taken by the Japanese Space Agency (JAXA).JAXA
JAXA tried again with a second, improved Hayabusa that worked in the same way. This time, the first projectile fired at the Ryugu asteroid was a two-kilogram piece of copper intended to open a small crater from which the sample would be taken. The second, tantalum. Why copper and tantalum? In order to be able to easily distinguish its residues when analyzing the material, which is essentially composed of silicates. Hayabusa 2 collected five grams of granules, enough to fill a teaspoon. But still five times more than the technicians expected.
But the mission is not over yet. Now, Hayabusa 2 continues its path toward an encounter with another asteroid that doesn’t even have a name: 1998 KY26. Arrival date: July 2031.
Visit to the Wild Comet
In 2004, NASA’s Stardust probe had a different goal: to obtain samples to study the composition of the gas and dust cloud around the nucleus of Comet Wild. Since most of them were grains with a diameter of barely a micrometer, the technique for collecting them was different: on board the capsule was a kind of tennis racket, in which the string was passed through a block of airgel, the crystalline substance of light, which is known to have been replaced. Almost, almost a smoking pill.
During the 10-hour dive into the comet’s cyclone, the probe raised its paddle to capture the particles embedded in the gel. It didn’t matter that they were tiny. The scientists knew their sample had to be analyzed grain by grain.
A similar system would soon be deployed on the Genesis capsule, this time to measure the solar wind, the stream of particles continuously emitted by the sun.
Of course, the capturer would not be an airgel, but rather a selection of highly pure crystals chosen to capture particles with different properties and energies. Protons, helium nuclei, and ions of heavy elements would strike it at speeds of hundreds of kilometers per second, burying themselves in the layers of silicon, corundum, niobium, nickel, gold, sapphire, or artificial diamond that covered the bottom of a collector this size of a paella
After a few months in space, the samples would return to Earth aboard a small re-entry capsule. He fell dangling from a parachute in a remote Utah desert. Since the glass was very fragile, helicopters piloted by Hollywood’s best stuntmen were responsible for “catching” it in the air before it collided with the ground.
The best laid plans fail for the most ridiculous reasons. When assembling the vehicle, the engineers installed the deceleration sensors that were supposed to deploy the parachute upside down. The capsule fell, tumbled and hit the hard desert floor.
Many glasses were broken, but others survived, despite being contaminated with dust and oxygen from the air. The scientists responsible for the experiment spent more than three years putting together the 15,000 pieces of the puzzle and cleaning the outer layers with ultrasound. They then turned to particle beam erosion. After all, the trapped atoms had not broken in the collision; They were hidden just 20 nanometers beneath the layer of desert dust.
In the case of OSIRIS-REx – a twisted acronym that has nothing to do with ancient Egypt, but rather the acronym for “Origins”, “Spectral Interpretation”, “Resource Identification”, “Security Regolith Explorer” in English – that was Targeting an asteroid again As with the Japanese probes, it was almost impossible to land there, as the slightest rebound would be enough to send the vehicle back into space.
In this case, the probe descended very gradually until its sampling arm with a cup at the end touched the ground. At that moment, he released a jet of pressurized nitrogen that stirred up the soil like sand in an aquarium. The head held around 250 grams of material, significantly more than the expected 60 grams, at least. So much so that there was difficulty closing the lid and some of the sample escaped into space.
The next phase was to place the container in the re-entry capsule and begin the long journey home. Just arrived.
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