NASA’s DART spacecraft spots its target, the asteroid it will collide with to save Earth from future impacts

The countdown has begun, the collision with the asteroid Dimorphos will take place on September 26. The objective is to test whether we have the capacity to divert an asteroid from its natural trajectory. If the mission is successful, it will be a milestone, the first time that the humanity is able to modify the dynamics of a celestial bodyComputer simulations and laboratory experiments will help interpret the trial collision, revealing what strategies could save Earth from a real threat.On November 24, 2021, the DART mission (Double Asteroid Redirection Test or Redirection Test of a Binary Asteroid) was launched into space from the Vandenberg base in California, with a clear objective: to intentionally collide with an asteroid to divert its trajectory and thus prove that it is possible to stop an alleged Armageddon. That is, discover if we are prepared to prevent a meteorite from reaching our planet and destroying it. After almost ten months of flight, the NASA spacecraft already has its goal in sight. The Space Agency has published the first image captured from the spacecraft. It is a binary system of asteroids relatively close to Earth, formed by Didymos, about 780 meters in diameter, and Dimorphos, about 160 meters, which is the one against which the impact will occur. The asteroid Didymos and its moon in orbit Dimorphosniusdiario.esThe collision, on September 26The impact against Dimorphos will occur in less than two weeks, on September 26, and the event will be broadcast live. Although neither of the two asteroids constitutes a danger to us, the test is part of NASA’s Planetary Defense program, it will be the first of its kind in the world. The crash will take place 11 million kilometers from Earth, when the spacecraft, the size of a vending machine, crashes into the small asteroid at 6 kilometers per second. The hope is that the collision will push Dimorphos into a closer orbit around its larger companion, Didymos, shortening its orbital period from nearly 12 hours to a few minutes. A successful attack would support the idea that similar efforts in the future could divert threatening asteroids onto safer courses. But new simulations and laboratory experiments show that the fate of the mission depends largely on a crucial question: Are these small asteroids solid rocks or, as astronomers increasingly believe, loose piles of debris? The answer, which should revealed from the crater and ejecta produced by the DART collision, will provide valuable information. “The important thing is to observe how that rock reacts, to know not only if it deflects, but also if it fragments when receiving the impact,” Isabel Herreros, the only Spaniard participating in this NASA mission, told NIUS before the launch. “That will help define what the strategy would be when attacking a meteorite in a serious case,” she clarifies. “Perhaps it turns out that we have to make a slower impact or that the kinetic impact directly is not the solution.” Small asteroids, a real threat Dimorphos-sized asteroids are thousands of times more likely to hit Earth than larger ones that have triggered mass extinction events in the past, and are capable of devastating a small state or country, making them a top priority for planetary defense efforts. The problem is that they are nothing more than points of light for ground-based telescopes, which makes them difficult to detect, let alone study. When detected, binary asteroid systems are very revealing, because their light dims each time. that one body blocks the other. By monitoring tiny fluctuations in light from Dimorphos and Didymos, NASA scientists have learned how fast they spin and the frequency of the smaller body’s orbit. This knowledge allowed them to design an autonomous navigation system that, with the help of a new solar-powered ion thruster, will steer DART as it approaches its prey. What happens next is anyone’s guess. “People assume it’s a solid rock, we have a solid spaceship that we’re going to hit it with, playing a kind of space billiards… but we really don’t know what it’s made of and what’s going to happen,” says Cristina Thomas, a planetary scientist from the University of Northern Arizona who leads the observation team for the DART mission. that not all asteroids are solid, monolithic rocks have accumulated in recent years.In 2019, Japan’s Hayabusa2 probe fired a 2-kilogram copper projectile at asteroid Ryugu, creating a surprisingly large crater, 14 meters in diameter The experiment indicated that the surface of Ryugu was not very consistent.The following year, NASA’s OSIRIS-REx probe landed on the asteroid Bennu and sank with little resistance.These missions confirmed the idea of ​​as weak theroids and restricted their surface strength: how much force is needed to deform objects. Scientists estimated that these asteroids were held together by about 1 pascal, the pressure of a piece of paper resting on your hand. Andy Cheng of the Johns Hopkins University Applied Physics Laboratory. “It reinforces a lesson we’ve learned from planetary geology for decades: You can’t tell if something is a rock by looking at images.” Unfortunately, predicting the consequences of an impact is much more difficult when the target is made up of thousands of loosely bound rocks. than when it is a solid rock. If DART hit a weak target made up of a pile of debris, the resulting crater would develop over the course of a few hours, a process that would take months or even years to model with traditional computer simulations, says Sabina Raducan, a planetary scientist at the University from Bern. Recently, she and her colleague optimized computer code that models a 3D shock wave to speed up the calculation to a few weeks. Unexpectedly, the new simulations show that the DART impact could transfer four to five times more momentum to a weak target made up of debris than to an absolutely solid one, enough to reshape the entire asteroid instead of just leaving a small crater of debris. impact. In this case it is believed that DART could propel the asteroid forward like a rocket booster. Different scientists have spent months simulating the impact on a weaker asteroid in the laboratory and in all cases it has been shown that their explosions are much more dramatic than in more compact asteroids. A team of instruments will observe on September 26 if the actual collision matches the simulations.Recorded with two cameras and broadcast liveDuring the days remaining until the day of the collision, in thirteen days, the spacecraft will carry out rounds of observation every five hours, after which the ground team will correct the ship’s trajectory, reducing the margin of error more and more each time. After the third and final maneuver, which will take place on September 25, about 24 hours before impact, the technicians will know the position of the target with a margin of only 2 km. From there, DART will be completely alone to guide itself autonomously until its final collision with the asteroid’s small moon. The impact will be captured by a small secondary ship, a CubeSat called LICIACube, weighing just 14 kg and manufactured by the Italian Space Agency (ASI). LICIACube has an autonomous navigation and communication system with the Earth, as well as two cameras that, during the collision, will take images every six seconds and show whether the mission has finally been successful. We won’t have the full picture for four years, when the European Space Agency’s Hera mission arrives to inspect Dimorphos’ surface and measure its mass. What is discovered then will serve to understand the internal structure of the asteroid and will help in future planetary defense missions. In the case of a real asteroid threat, the goal is to hit the body hard enough to deflect it, but not hard enough to vaporize it and send a storm of small rock fragments toward Earth. Confirm that Dimorphos has a debris structure as well it would shed light on a more important question: how the Solar System first formed. “Understanding what these small bodies went through helps us understand how planetary systems formed,” says planetary scientist Julie Brisset of the Florida Space Institute. “It’s the leftovers from this process.” So scientists wait anxiously as DART approaches its target, hoping that after the impact some secrets of the universe will be revealed.