A probe as a cosmic cue to tap away an asteroid

Pandemics, earthquakes, volcanic eruptions, wars, climate change. There are a whole lot of disasters that can affect us as humanity. But none are potentially as devastating as a giant asteroid colliding with Earth.

65 million years ago, the dinosaurs died out en masse when that happened. The chance is nil in the short term, but such a collision is going to take place again. So we better prepare for it and try to prevent it, find space organizations.

NASA is launching a vehicle towards a double asteroid tomorrow morning for a unique test. Can we change the orbit of a celestial body by aiming at a high speed probe, as a cosmic cue? The DART mission must answer whether that is a real way to save us from a asteroid on collision course with the Earth.

Collision at 22,000 kilometers per hour

DART stands for Double Asteroid Redirection Test. The mission goes to a double asteroid. To Didymos – diameter 780 meters – circles the moon Dimorphos – diameter 160 meters. The NASA probe will arrive at the end of September next year, when the asteroids are 11 million kilometers away from Earth. Then the intention is that the vehicle will pop on Dimorphos at 22,000 kilometers per hour.

A double asteroid was deliberately chosen, says astronomer Lucas Ellerbroek: โ€œIt‘s easier to make a change in the orbit of the small asteroid around the great asteroid than the orbit of a asteroid around the sun.โ€ A satellite from the Italian space agency ASI and a probe of the European space agency ESA capture images and take measurements of the impact.

When changing the job, we should not imagine too much. โ€œIt’s like shooting a pea on a basketball,โ€ says Ellerbroek. If the mission succeeds, the job will shift a fraction of a percent, says NASA. โ€œBut a small change in job can make a big difference, if you do it early enough. The sooner you hit a asteroid, the smaller the push has to be.โ€

A little push can change the track considerably:

Didymos and Dimorphos are not a threat to the Earth themselves. Over the next hundred years, we don‘t have to worry about space objects larger than 140 meters that may collide with the Earth, says NASA, although we only know an estimated orbit of 40 percent of those objects. They can theoretically put a city in ruins, or cause โ€œregional devastationโ€ as NASA describes it. Ellerbroek: โ€œYou better have practiced once if it’s really necessary.โ€

The asteroid that sealed the fate of the dinos had a cross section of ten kilometers. Those objects are even rarer, says Ellerbroek: โ€œWith every increase of a factor of 10 in size, an increase of a factor of 1000 should be in rarity.โ€ And the larger an object, the sooner you detangle it and the more time you have to come up with a plan to prevent a collision.

A plot like that of sci-fi film Armageddon from 1998, in which scientists only remarked eighteen days in advance that a asteroid the size of the state of Texas is on Earth is mainly fiction and little science.

Nuclear blast

The method they choose there for planetary defense – blowing up the asteroid with an atomic bomb – is also not preferred. A โ€œnon-nuclear kinetic impactorโ€ has so far been the โ€œmost mature approach,โ€ NASA wrote in 2007. A nuclear blast may be ten to a hundred times more effective, but has major โ€œoperational and development risksโ€. โ€œIf things go wrong,โ€ says Ellerbroek, โ€œradioactive debris may land on Earthโ€.

It also depends on what exactly the object that comes to Earth consists of. Is it a porous asteroid or a hard-hitting comet? The DART mission also looks at the chemical composition of the asteroid. In this way, NASA‘s computer models can be improved that calculate which collision is most effective, should it really be necessary to give an asteroid an uppercut into the universe. Whether that’s the case in a hundred, a thousand or a million years.