SPACE – It’s a scenario worthy of the movies Armaggedon et Don’t Look Up. What if a asteroid was to rush straight to Earth? A hypothesis seriously studied by the Nasa and the European Space Agency (ESA), which devote the missions DART and HERA, as you can see in the video above.
What is the DART mission?
This mission began on November 24, when the space agency sent a spacecraft aboard a Falcon 9 rocket. This module should crash on the night of September 26 to 27 at 1:14 a.m. French), at a speed of 24,000 km/h on the asteroid Dimorphos, a small « lune » which revolves around a larger asteroid, Didymos, located 11 million kilometers from Earth.
“The Dimorphos target is the perfect size for this type of mission, because it’s really the size of an object that could be a problem for us one day.details at HuffPost Naomi Murdoch, one of the scientists on the DART mission. Why ? Because there are a lot of asteroids of this size that we don’t yet know about and that’s really where a threat could come from one day. » Rest assured, Dimorphos does not represent a threat to the Earth: its orbit around the Sun passes, at its closest, only 7 million kilometers from us.
The moment of impact between the spacecraft sent by NASA and the asteroid promises to be spectacular, and can be followed live on the American agency’s video channel. This life-size experiment aims to modify the period of revolution of the small asteroid around the larger one. “Right now it takes 11:55 for Dimorphos to go around Didymos. It is believed that the DART impact will decrease the period by 10 minutes”, says Naomi Murdoch. Returned to the terrestrial scenario, the objective is to know if humanity is able to voluntarily modify the trajectory of an asteroid which would threaten our planet.
A kamikaze space mission
To hit such a small target, the ship will steer autonomously for the last four hours, like a self-guided missile. His camera, called Draco, will take at the last moment the very first images of the asteroid, whose shape we do not yet know. At a rate of one frame per second, visible live on Earth with a (small) 45 second delay.
Three minutes after impact, a shoebox-sized satellite, called LICIACube and released by the craft a few days ago, will pass about 55 km from the asteroid to capture images. They will be sent back to Earth in the following weeks and months. But to have real data on the impact of DART, we will have to wait for the European HERA probe.
This probe must take off in October 2024 for an arrival in 2026 on Dimorphos. Objective: return to the “crime scene” to assess the consequences of the impact of DART. “She will give us the detailed result in terms of the size of the crater. But it will also give us, for the first time, detailed information on the internal structure of an asteroid. It was never done. And this thanks to a radar whose expertise is French”explains Patrick Michel, research director at the CNRS and scientific manager of the Hera mission at ESA.
Scientists expect to be surprised by the results of the investigations. Because “we ignore almost everything” of these celestial bodies, indicates the astrophysicist. “It’s a new world that we are going to discover”. For him, the asteroids are not just boring pebbles in space, but fascinating and complex little geological worlds, with craters, basins, rock fields, particle ejections… »
But science struggles to understand these territories because on their surface, gravity is very weak compared to that of the Earth: the behavior of matter there is “Totally counter-intuitive, we cannot rely on images to know how asteroids behave, we must also ‘touch’ them”insists Patrick Michel.
Go back to the origins of the solar system
Binary systems, such as Didymos and its satellite Dimorphos, represent about 15% of known asteroids and have so far not been explored. Shape, mass, chemical composition, internal structure, impact resistance, shape of the crater caused by DART: HERA’s instruments should reveal the secrets of Dimorphos. At the end of the mission, a micro-satellite will even land on its surface to measure how it bounces.
“Today we are in an era where all solid surfaces in the Solar System have craters. To get back to the original scenario, we need to understand what happens when two bodies collide.”. Not in the laboratory, but on a real scale thanks to the DART-HERA couple, the scientists hope.
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