A few hours ago, around a quarter past nine at night Spanish peninsular time, a NASA probe collided with an asteroid near Earth . The US administration has completely lost contact with the ship. Future research will clarify the seriousness of the matter. But not the causes, because we have that very, very clear: this collision has been intentional . It has in fact been the main objective of the DART mission , which was launched on November 24, 2021 aboard a SpaceX Falcon 9 rocket. Since then, the probe, which receives the same name as the mission, DART, has been directed to its objective, the small moon that orbits the asteroid 65803 Didymos , to collide with it and study how said collision is capable of altering its trajectory around of the main asteroid.
Didymos is a small asteroid of the type known as a Near Earth Object (or NEO). These objects are those whose orbit brings them very close to our planet. If they also cross the Earth’s orbit on their path around the Sun and have a diameter of more than 140 meters , they are also considered as Potentially Hazardous Objects. Didymos meets both requirements, since its orbit crosses that of the Earth and it has a diameter of 780 meters . This asteroid was discovered in 1996 , although the moon that orbits it was not discovered until 2003. The satellite is called Dimorphos and has a diameter of about 170 meters , orbiting around Didymos about 1,200 meters away and taking almost 12 hours to complete each orbit.
NASA’s DART mission aims to impact the moon Dimorphos , to study how this collision affects its trajectory. This is the first mission whose main objective is to investigate ways to defend ourselves against potentially dangerous asteroids. We believe there could be several thousand objects larger than 140 meters in diameter whose orbit would make them pass relatively close to the Earth , of which we have a few hundred under control, although we are very confident that none of them will impact the Earth during this time. century. Well, on September 26, 2022, DART collided with this satellite, slightly changing its trajectory . It is still too early to know if the effect of this collision has been as expected, but in the next few days we should receive the data collected by the LICIACube nanosatellite , which separated from the main impactor 10 days before the collision and followed in its wake precisely to carry out this subsequent study.
In addition to this follow-up immediately after the impact, since LICIACube will fly over the moon Dimorphos just three minutes after the collision , the European Space Agency is developing a mission that will study the system in detail in 2027, when it arrives in the system after being launched in 2024. This ESA mission will be called Hera and will carry two nanosatellites, Milani and Juventas, on board.
This mission aims to study the possibility of avoiding a future collision of one of these NEOs with our planet. The advantage of this type of maneuvering is that, if we were to discover an asteroid that was going to hit the planet years ahead, a small push from a probe hundreds of times smaller would be enough to change its trajectory and avoid the collision . Other methods of avoiding this type of catastrophe have been proposed, although few of them compare in efficiency and cost to the one studied by the DART mission.
Other proposals would include the detonation of nuclear bombs on the asteroid’s surface, or the installation of a reflective surface , probably composed of white paint, that would reflect sunlight, weakly but steadily propelling the asteroid in the opposite direction. Another option would be to shine a powerful laser on it, so that a tiny region of its surface would heat up considerably and function as a temporary rocket. The option of exploding powerful bombs on the asteroid would not work, for example, for asteroids whose surface is made up of loose material and not solid rock, since what we would achieve is to create a huge cloud of millions of fragments more than to deflect the asteroid. On the other hand, the options of covering the asteroid with a reflective coating or illuminating it with a laser would not work for very fast-rotating asteroids . In addition, all these proposals are considerably more elaborate, complex and expensive than that of making a small object collide at high speed with the asteroid, which has the advantage of working with any type of asteroid .
Hopefully this mission and future efforts in this direction can prevent the apocalyptic ending portrayed in movies like Armageddon or Deep Impact . Hopefully, our response to this threat, if it ever happens, will be smarter than the one shown in the movie Don’t Look Up .
2021, Double Asteroid Redirection Test (DART), Planetary Defense Coordination Office, NASA
2021, DART, ESA