Planetary Defense: Man’s First Attempt to Deorbit Asteroids

For the first time, humanity will attempt to de-orbit a space rock. If dinosaurs had thought about it, they might still be alive, having avoided a large asteroid falling on Earth – and on their heads – 66 million years ago.

On Monday night, humanity’s most forward-thinking and resourceful will try exactly what we’ve already seen in science fiction movies: deflect an asteroid off course by launching a car-sized spacecraft, DART, at it like a rocket. (Double Asteroid Redirection Test) of the American Space Agency (NASA).

The $330 million and 550 kg cubic DART robotic craft, after traveling a distance of about 11 million kilometers from Earth, from where it was launched in November 2021, is destined to crash – at 02:14 Greek time on Tuesday, September 27 – to the small satellite Dimorphos (160 meters in diameter) of the larger asteroid Gemini (about 780 meters in diameter). It is the first critical “rehearsal” of planetary defense in case such a space rock poses a threat to Earth in the future.

This is the first test of a technology to deflect/avoid a potentially destructive asteroid. The DART spacecraft impacting the asteroid at about 22,000 kilometers per hour will aim to use kinetic energy to slightly deflect it from its orbit. Something similar may need to be done in the future with another large asteroid whose orbit is in danger of crossing that of our planet.

The “bombardment” of Dimorphos – which will result in the destruction of DART – is expected to alter its orbit slightly (by about 1%) so that it orbits Gemini a little closer and faster. Telescopes from Earth will be watching to see if this actually happened.

At the same time, DART has already released since September 11 the small (weighing 14 kg) Italian-made LICIACube spacecraft that will approach Dimorphos at a distance of 55 kilometers and with its cameras will photograph the effects of the impact. The event will also be monitored by various ground-based and space-based telescopes, including the James Webb.

The US mission will be followed by the European Space Agency’s (ESA) HERA mission, which will send a German-made spacecraft, accompanied by two microsatellites (cubesats Milani and Juventas), to Gemini and Dimorphos to study them more closely. and see firsthand the crater that will have been created, as well as the other effects of the DART impact. HERA is expected to launch in 2024 and reach the asteroid and its moon in late 2026.

If DART fails to find its target, it has enough fuel to give it another chance in two years to try again at another space rock. The Johns Hopkins University Applied Physics Laboratory in Baltimore is responsible for the mission.

NASA has found more than 27,000 asteroids of various sizes whose orbits bring them close to Earth. Despite advances in detecting asteroids that occasionally approach our planet, so far astronomers estimate that only 30% to 40% of near-Earth objects larger than 140 meters in diameter have been detected. That’s why it’s been realized that there must be a planetary defense technology ready in case of a nasty surprise from above, such as the 10km-diameter asteroid Chicxulub that crashed into present-day Mexico and probably wiped out the dinosaurs 66 million years ago.

However, if ever – the unborn – humanity needs to derail a very large asteroid, such as the one that wiped out the dinosaurs, the spacecraft that will crash into it will most likely be carrying a nuclear bomb or other powerful explosive. In any case, the risk of needing such a planetary defense mission is very small (though not zero) for at least the next century, according to NASA calculations.

China is preparing a similar planetary defense mission to asteroid Bennu in 2026.

NASA TV and ESA TV will broadcast the DART impact live, as well as NASA’s social media (Facebook, Twitter, YouTube).

RES-EMP

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