NASA announces "extremely small" chance of collision with an asteroid in 2182

In September 2135, the asteroid Bennu, 500 meters in diameter and in the shape of a space dice, will make a visit to Earth, passing half the distance from the Moon. Most likely, the gravity of our planet changes its trajectory at that moment, making it a tremendous challenge to calculate exactly where it will go. But there is an "extremely small" chance that it will pass through a "gravitational keyhole" that will put it on an impact path with Earth in the late 22nd century, in 2182. NASA had issued a press call for communicate an “important finding”, but one that will affect those who inhabit the Earth in more than a century.

The asteroid Bennu travels at about 100,000 kilometers per hour: if it hit Earth, it would release an energy like 70,000 atomic bombs from Hiroshima and create a crater about five kilometers in diameter, according to the most up-to-date calculations that NASA had done so far.

At the time of making these estimates, the accumulated probability of impact between Bennu and the Earth was only 0.037% and would not happen for about 150 years: in the time interval that goes from the year 2175 to 2196, almost in the XXIII century.

According to the new NASA study, the probabilities that they will collide sometime up to 2300 are 0.057%, still tiny.

But the key date is September 24, 2182, when they could crash, if all goes wrong.

How to alert humanity to the danger of a potentially fatal asteroid

"No object is going to hit the Earth in the next 100 years"

To avoid that hypothetical scare, Chinese scientists had recently raised the possibility of removing Bennu from our path using 23 rockets against the asteroid. At the moment, NASA's DART mission is heading towards a small asteroid, called Dimorphos, with the intention of changing its trajectory and verifying that they are capable of doing something like this at those distances and speeds, more than 20,000 kilometers per hour. Although NASA assures that no asteroid is known, at the moment, that represents a risk of impact on Earth in the next 100 years, the truth is that it is advisable to prepare, because it is estimated that there are about 15,000 potentially dangerous asteroids to be discovered. DART is the first planetary defense mission and its intention is to collide with Dimorphos next summer to divert its course.

To study in detail the potential danger of Bennu, NASA sent the OSIRIS-REx probe there in 2016, which has been mapping that little world worthy of the Little Prince. After 27 months of space travel, the spacecraft arrived at the asteroid in December 2018 and since then, it has been orbiting it to learn all its secrets. "The OSIRIS-REx data gives us much more precise information, we can calculate the future trajectory of Bennu with a high degree of certainty until 2135," said Davide Farnocchia, lead author of the study on the trajectory of the space rock and scientist at the Center. of Near Earth Object Studies of NASA.

"We have never before modeled the trajectory of an asteroid with this precision," added Farnocchia, who has developed detailed calculations to model Bennu's path for centuries to come. So the key is to know if Bennu will go through one of those "keyholes" that would put the asteroid on the way to generating an Earth catastrophe. That probability is "extremely small" according to NASA. However, Farnocchia stressed, the real risk of Bennu is less than that of all unknown dangerous objects and that they should be located as soon as possible.

Astrophysicist Javier Licandro, who has participated in several studies of the OSIRIS-REx probe, points out that "they have been able to greatly refine Bennu's orbit by integrating all the factors that may be minimally affecting". According to Licandro, from the Instituto de Astrofísica de Canarias, researchers have ruled out many possible impact trajectories, greatly reducing any probability of impact by 2035. “And they maintain a probability of impact of 1 in 2,700 for September 2182: it is not that there is a extremely high probability, but it is not one of the smallest, it is one of the known objects with a high probability ”, warns Licandro. "It is among the potentially dangerous because Bennu is very large, half a kilometer of a bug, and if it hits the Earth it could generate very great damage," adds the expert.

"Bennu is among the potentially dangerous because it is very large, it could generate very large damage"

Javier Licandro, IAC

"NASA's Planetary Defense mission is to find and monitor asteroids and comets that can get close to Earth and pose a danger to our planet," said Kelly Fast, head of the Near Earth Object Observation program.

The probe came to meet Bennu because it has many characteristics that make it an interesting rock for science: it can reach our planet, as we see, and its composition also allows us to venture what the Solar System was like more than 4,000 million years ago and how life arose on Earth.

Life on asteroids

The probe collected 60 grams of minerals with its robotic arm in October 2020, after dropping slightly against the asteroid to take samples, before circling Bennu a few more times and heading for Earth. The spacecraft will orbit the Sun twice, covering 2.3 billion kilometers to return to our planet. But it will not settle: from space it will launch the capsule containing those 60 grams, which will fall in the Utah desert on September 24, 2023. NASA is considering using the probe, of about two tons, to board another asteroid, already that you have enough fuel left over.

However, this mission is not the first round trip to an asteroid.

The Japanese probe

Hayabusa

landed on the asteroid Itokawa in 2005 and returned five years later with samples that have made it possible to study its composition.

Later, the

Hayabusa 2

brought back samples from the asteroid Ryugu, "a lot of particles" that landed in December 2020 in a capsule in the middle of Australia.

Since then, its composition has been analyzed, in principle quite similar to that of Bennu.

"NASA's Planetary Defense mission is to find and monitor asteroids and comets that can approach Earth and pose a danger to our planet."

Kelly Fast, NASA

The surprises with Bennu came early on, as Lori Glaze, NASA's Director of Planetary Sciences said: “The first three months of OSIRIS-REx's detailed research on Bennu has reminded us what the discovery is about: surprises, think fast and flexibility ”. The asteroid turned out to be much less solid than expected, with permanent activity such as ejection of small rocks and columns of particles. Traces of liquid water were also observed, which must have been present in a much larger asteroid than the one Bennu broke off at some point.

Not only do asteroids kill life, as we know from dinosaurs, but they also have great potential to take it to other worlds. Or, at least, the basic ingredients for that life, more or less sophisticated, to emerge. For decades, organic compounds have been found in meteorites that reaffirm the hypothesis that these essential elements for life to emerge on Earth came from space aboard asteroids. And also the water, essential for the spark to emerge, came to us in space rocks.

Only 25% of Bennu's material will be immediately analyzed by scientists: most of it, the other 75%, will be left for future scientists with future new technologies and knowledge to get the most out of these unique samples. Bennu and Ryugu are primitive and very dark asteroids and are composed of elements based on carbon and hydrated silicates, which were in contact with liquid water. NASA already has another mission ready, with the

Lucy

probe

, to travel to the Trojan asteroids that orbit Jupiter.

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