On Wednesday morning, the spacecraft Dart from Nasa will be sent towards the asteroid Didymos. In early October next year, the probe will crash straight into Didymos’ moon Dimorphos.
The purpose is to test how a defense system against asteroid impact could work.
– We call ourselves the planet’s defenders. We’re defending the Earth, says Angela Stickle, a planetary geologist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, USA and leader of one of the research groups at Dart.
In the disaster movie “Armageddon”, Bruce Willis detonates a giant asteroid heading towards Earth with a nuclear charge. But the method that would work in reality is instead to shoot a space probe at the asteroid to push it in another direction.
– Darts is a test of the technology that we may need to protect the planet. Now we are testing it so that we can be ready if needed in the future, says Angela Stickle.
Sooner or later Earth will be hit by a large asteroid again.
– The earth is bombarded every day, by pebbles, gravel and dust. If you see a star fall, it is a small meteorite that comes in, says Angela Stickle.
Both Nasa and the European Space Agency This follows the asteroids in our solar system and publishes daily updated lists of those that may be a threat to us.
– We do not know of any asteroid on its way to us that would be large enough to penetrate our atmosphere and be a danger to us for the next 100 years. But our biggest concern is things that may be out there that we do not know.
Really large asteroids, such as the one that exterminated the dinosaurs, with a diameter of one kilometer or more, reflect a lot of light and are easy to spot. The biggest danger is instead celestial bodies that are around 100 meters in size. Such an asteroid probably crashed on the river Steniga Tunguska in Siberia in June 1908, destroying 2,000 square kilometers of forest. The asteroid that exploded over the Russian city of Chelyabinsk in February 2013 was much smaller, about 20 meters or as big as a bus. But the shock wave it created still injured more than 1,200 people when windows were smashed.
– There we did not have much warning. It came from a direction where it is difficult to observe, and we did not know that there was anything there, says Angela Stickle.
Rymd probe darts will then crash into Dimorphos to push it. Astronomers on Earth can then see how the collision affects the moon’s orbit.
– The system with Didymos and Dimorphos is the perfect natural laboratory to test this. Seen from Earth, Dimorphos orbits in front of and behind Didymos, so that the light that reaches us becomes weaker and stronger. Therefore, we know exactly how long a lap takes. It is also close enough to the earth so that we can follow what is happening with the help of telescopes – but not so close that there is any danger for us.
Dimorphos is also 160 meters large, and thus of the same size as the most dangerous asteroids can be.
This is how you know if the experiment was successful
As Dimorphos passes, the brightness of Didymos decreases. The so-called light frequency will slow down if Dart manages to collide with Dimorphos.
Source: Nasa, Esa. Graphics: Maria Westholm.
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In three years also plans Esa to send up a space probe, Hera, to Didymos and Dimorphos to study the effects of Darts crash landing in detail up close.
– Asteroid impacts are the only natural disasters we can prevent and protect against. As a planetary scientist, I do not often get the opportunity to see how my work can directly benefit humanity. It’s really rewarding, says Angela Stickle.