A few hours ago a SpaceX Falcon 9 rocket launched the DART (Double Asteroid Redirection Test) mission to the asteroid Dimorphos, which is the moon of the asteroid Didymos. The goal is to crash into it to see if, if necessary, we would be able to deflect an asteroid coming towards Earth.

Deflect an asteroid

The DART impactor is a cube about 1.3 meters on a side – solar panels aside – that will have a mass of about 550 kilograms when it hits Dimorphos. The impact, scheduled for October 2, 2022, will occur at 24,000 kilometers per hour. It is expected to slow the asteroid by about 1.4 meters per hour, although the final figure will depend on the composition of the asteroid and whether it is more rocky or porous.

This will cause the distance at which Dimorphos orbits Didymos to be reduced, thereby also changing the period of its orbit, which will be reduced by up to about 10 minutes. The Italian Space Agency’s Cubesat LICIACube will be there to image the impact, although it is not equipped to measure the variation in Dimorphos’ orbit.

But since Dimorphos eclipses Didymos when we look at them from Earth, we will also be able to check this reduction in the period of its orbit by observing it with ground-based telescopes. And for 2024 is planned the launch of the HERA mission of the European Space Agency, which by 2026 will place a satellite in orbit around Didymos to check in situ the effects of the impact.

Earth-threatening asteroids

The idea of this mission is to check if we would be able to divert the trajectory of an asteroid that would represent a danger to us if we discovered it in time. The time is necessary because the change that would be imparted to its trajectory would be minuscule, so it would take time for it to be large enough to dodge us.

So apart from testing methods to deflect asteroids we can’t stop looking to the sky to find them in time. It is estimated that we have not yet found 60% of the asteroids of a similar or larger size than Dimorphos. And Dimorphos is big enough to take out a city and its metropolitan area. Although it is also true that of all the potentially dangerous asteroids that we have catalogued, none of them pose a danger of impact in the next 100 years.

Just as Didymos and Dimorhos do not, not even if we change the orbit of the latter around the former, since the orbit of Didymos never crosses that of the Earth.

Projects such as the NEO Surveyor, a space telescope designed to search for asteroids, which could be launched in 2026, or the FlyEye ground-based telescopes of the European Space Agency, may be those eyes we need to avoid ending up like the dinosaurs, since we are supposed to be a little smarter than them. And of course its implementation should be an international priority in which all the space agencies of the world should collaborate.


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