What NASA plans to do with Demorphos and Dart

IOn Tuesday night, a $330 million spacecraft will collide with the asteroid Demorphos. It is no coincidence that their nickname “arrows” reminds us of small arrows that are thrown at targets. The accident was entirely intentional. NASA launched the probe, which has the mass of a small car, into space specifically to crash it into Demorphos at a speed of 23,800 kilometers per hour. A little roboprop from Italy posted earlier will capture it all.

Ulf von Rauchaupt

Editor in the “Science” section of the Frankfurter Allgemeine Sunday.

What refused it? Well, one would like to see if such a collision was enough to change the course of Demorphos. Because Brocken is 163 meters tall. Asteroids of this caliber are the most dangerous in terms of potential collision with Earth: they are large enough to cause a national catastrophe at the point of impact. At the same time, they are so small that we know very little of them.

It is currently known that approximately 30,000 celestial bodies – most of them asteroids – approach or even cross the Earth’s orbit as it orbits the Sun. Two-thirds of them are smaller than 140 m and therefore relatively non-critical. When they fall to the ground, they burn up in the atmosphere. Only the largest of them reaches the deeper layers of the air. However, it is not always completely harmless. A twenty-meter piece that fell in Russia in 2013 only disintegrated at a low level causing an explosion wave. Windows smashed throughout the area, injuring more than a thousand people.


Photo: FAZ

We don’t have to be afraid of really big cars right now either. A ten kilometer asteroid, like the one that wiped out the dinosaurs and means at least the end of human civilization today, only hits Earth every hundred million years. Such a collapse on the ground is too great for researchers to escape. Thus, a catastrophe of this kind is impossible within the next 100 years – however, future orbits of the asteroid cannot be predicted with certainty. In the case of rocks with a diameter of one kilometer – such rocks would still destroy an entire continent – we are 98% sure that none of them will hit us in the next 100 years.

But the problem is with asteroids from 140 to 1,000 meters in height – exactly those that are similar to Demorphos. There’s probably a lot going on in a safe collision course on Earth without us even knowing. Their effect would still be that of a very large atomic bomb. So, if the worst came to the worst, he could wipe out a large city.

What do you do if we suddenly discover one? If we are not so lucky, it will take several years to decades before the impact occurs and one can try to prevent the catastrophe. Because a small push is enough to change its orbit so that it misses the Earth. To do this, one could shoot an asteroid with a laser, for example, or with sunlight collected from a concave mirror placed in space. Or detonate an atomic bomb near its surface. However, the simplest thing is to have a targeted crash, like the one being experienced on Dimorphos now.

By the way, it is just a test object and not a danger itself. Also, there is no way that Dart accidentally kicked him to the ground on Tuesday. Demorphos is a small moon. Every twelve hours it orbits a slightly larger asteroid, and the collision will shorten that orbit by just 4.2 minutes — if the experiment is successful and Dart can transfer its kinetic energy to mass sufficiently.

More answers to curious kids' questions

More answers to curious kids’ questions

An illustrated collection of articles has been published from our column “How do I explain it to my child?” by Reclam.

To the publisher’s page

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