In science fiction movies, if someone is on an asteroid, they are probably mining some valuable metal, serving time as a prisoner for some interplanetary felony, or sacrificing their life to save the Earth from an imminent impact and hoping, perhaps, that baptize some institute in Idaho with his name. This Sunday, in the Utah desert, the prequel to those stories that we have seen many times and that does not envy the cinematic epic is recorded, although the action scenes are recorded by machines and humans only use their brains. There, at 4:55 p.m. on Sunday (Spanish peninsular time), a capsule with remains of Bennu is scheduled to arrive, a 500-meter-long asteroid that, according to the Palermo scale, is the most threatening to Earth. The event can be followed live on NASA’s YouTube channel in Spanish.
Although they do not risk their necks, saying that they are only putting their brains is also unfair to the engineers and scientists responsible for the NASA mission, the third that will bring remains of an asteroid to Earth, after the Japanese Hayabusa 1 and 2. The round trip mission to the asteroid Bennu, an object the size of a shopping center that circles the Sun between Mars and Earth, is a display of technical and scientific filigree. After a seven-year journey, it landed on the ground of Bennu, more than 300 million kilometers away from Earth. It approached its surface, landed on that body with a tiny gravitational pull, collected at least 250 grams of dust and rocks from its surface and rose again to begin its return journey.
As those responsible for the Japanese space agency JAXA, pioneers in sending spacecraft to harvest asteroid sand, already knew, placing a probe in the orbit of such a small body requires particular expertise. Rather than inserting itself into its gravitational field, as is done when visiting planets or moons, Hayabusa 1 caught up with the asteroid on its way around the Sun. Bennu, a little larger, has become the smallest object never orbited.
After arrival, the descent to collect the sample on an unknown surface is fraught with danger. In 2005, Hayabusa 1 was only able to collect a few particles from the asteroid Itokawa, after a failure in its collector, and that semi-success was not known until 2010, after a bumpy five-year return. Hayabusa 2, the improved version of its predecessor, managed to bring back five grams of the asteroid Ryugu, and the OSIRIS-REx capsule will multiply that amount by more than 50.
As Dante Lauretta, principal investigator of the mission, said, they expected it to be something similar to “a sandy beach” and it turned out to be much more rugged terrain, full of rocks up to ten meters high against which the probe could crash. Bennu looks more like a giant pool of balls floating together in space, a world much less compact than it appeared from the outside. When OSIRIS-REx descended to collect its samples, it encountered no resistance and sank half a meter to the surface, until the retrojets returned it to orbit. After overcoming these uncertainties and traveling millions of kilometers back to Earth, scientists and engineers assure that the capsule with its loot will crash, with surgical precision, in an area of Utah of about 600 square kilometers, equivalent to that occupies the city of Madrid.
When the military and scientists collect the capsule in Utah, they will send it with all precautions, so as not to contaminate the samples and prevent any extraterrestrial threat from escaping, to the Johnson Space Center in Houston. There, if there is no problem, the samples will begin to be analyzed and how they will be distributed among the world’s scientists interested in unraveling their secrets. This study, together with all the information collected by OSIRIS-REx during its visit to Bennu, will be a trip to the past to understand our origins and a preparation plan to avoid a space cataclysm. In Bennu’s crossing with Earth, which would occur on September 24, 2182, there would be an impact risk of one in 2,700, according to NASA.
NASA illustration of the OSIRIS-REx.AP probe
Asteroids are like fossils from the beginnings of the solar system and it is suspected that the water in the oceans could have come from an ancestral bombardment of these objects and that it was even inside them that the organic compounds that made the appearance of life possible arrived. Although meteorites from asteroids arrive continuously, going to one of them and bringing back unaltered samples has advantages, such as knowing what those rocks are like when they have not been exposed to natural processes on their journey to Earth.
“Meteorites of the carbonaceous chondrite class usually break away from their parent asteroids or comets thanks to an impact that favors the most resistant rocks (the others are pulverized or never reach the Earth’s surface, since their mass is lost in the phase). of fireball upon entering the atmosphere). Furthermore, chondrites usually take tens of millions of years to reach the Earth and, in their transit, they can be heated by the Sun or impact other objects,” explains Josep María Trigo, researcher at the Institute of Space Sciences (CSIC-IEEC). ), in Barcelona. There, they have a sample return and meteorite clean room where they have already studied the materials returned from comet 81P/Wild 2 and the asteroid Itokawa, and where they also aspire to analyze some samples from Bennu.
René Duffard, from the Institute of Astrophysics of Andalusia, CSIC, says that the work of these missions is also changing the idea we have about asteroids. Although there is a classification according to their composition, into carbonaceous, metallic or silicate, the arrival of probes has confirmed that they are “accumulations of debris”, which can be mostly of one type or another, “but which can incorporate surprises, because “In an accumulation of rubble you can find anything.” This explains the capacity for improvisation that those responsible for OSIRIS-REx have had to apply to adapt to the unexpected and the doubts that would be had, for example, about the best option to destroy or divert one of these objects if it were on its way to colliding with the earth.
In their role as fossils or pristine evidence, Duffard says that these orbital debris dumps, among other things, have “the advantage that they have remained there, in space, without any alteration during the 4.5 billion years since the formation of the Earth. ”. “Here on Earth there was movement of tectonic plates, erosion, rain and wind and the rocks were altered,” he adds. Furthermore, unlike meteorites, the information does not arrive decontextualized. “It’s the difference between an archaeologist, for example, receiving a bone that you don’t know where it was, or being told that it was found on a specific beach under certain conditions,” he says.
Knowledge of Bennu’s structure is also relevant if we consider the possibility of changing its trajectory to prevent it from falling to Earth. “In those cases, what we want is to transmit kinetic energy to the object and also have a lot of material released that generates additional propulsion,” explains Juan Luis Cano, coordinator of the NEOCC Information Service, of the European Space Agency, that monitors near-Earth objects. “This multiplier effect is different if one impacts a porous material (like Bennu), because the energy compacts the material instead of releasing it,” he adds. “That makes it more difficult for us to predict how much we will be able to change its trajectory,” he concludes. “Another aspect that has been studied with Bennu is the Tarkovsky effect, a very small force on asteroids, caused by solar radiation and how they absorb and radiate radiation from different faces, which, in the very long term, change their trajectory. This has been done with enormous precision and it has been possible to limit the estimate of the probability of impact with much more accuracy,” continues Cano. Missions like OSIRIS-REx will make it possible to be more prepared when future generations have to face one of these untimely encounters.
From the Utah desert, Lucas Paganini is one of the NASA scientists awaiting the timely arrival of this “time capsule that will tell us what was happening in the solar system 4.6 billion years ago.” “If asteroids have the necessary organic compounds or could have brought water to Earth, all essential elements for life, the question we ask ourselves is whether what happened here could also have happened on another planet, along with other stars, in other planetary systems,” says Paganini. “Or if it could have happened on one of Jupiter’s moons, although the conditions are different. That is the puzzle we are trying to decipher,” concludes the researcher.
While on Earth researchers search for the cargo released by OSIRIS REx and fantasize about what that content will tell us about the Earth’s past or the origin of life, the probe will already be preparing its next mission. After turning on its engines again, it will set off to meet the asteroid Apophis, which will pass by our planet in 2029, 30,000 kilometers away, one tenth of the distance that separates us from the Moon. Although scientists consider the crash unlikely, the information OSIRIS REx collects will help humanity prepare for any unforeseen event. Perhaps the probes also deserve, at least, a plaque in some institute in Idaho.
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