NASA prepares to launch a spacecraft to collide with an asteroid and divert its course | Science and technology

Asteroids form small and diverse geological worlds that tell a lot about how the solar system was formed, but information about them is still limited to this day … The Hera probe will be launched to discover these “unknown worlds” after the mission of the spacecraft “Dart” launched Monday by NASA. .

From Monday evening to Tuesday, NASA’s DART mission will attempt to divert an asteroid’s path by deliberately colliding with Demorphos, a small moon orbiting the larger asteroid Didymos, 11 million kilometers from Earth.

This experiment aims to reduce the duration of a small asteroid’s orbit around a larger asteroid, to see if humans are able to change the course of any asteroid that threatens Earth.

“Such a two asteroid system represents an ideal test for an experiment to defend life on Earth, and also constitutes a completely new environment,” said Ian Carnell, head of the European Space Agency’s ‘HERA’ mission.

The European probe Hera, named after the Greek goddess of marriage, Hera, will be launched in October 2024 and will reach Demorphos in 2026. The purpose of this probe is to preview the results of the DART mission.

The diversion test of the asteroid will be fully documented thanks to the information collected by the “HERA” instruments (cameras, lasers, high resolution imaging devices, radar …). These data will allow Earth defense experts to reliably improve models for extrapolating impact scenarios.

“We need to know the nature of asteroids and their components, because the degree of risk for each of them varies according to the different types of rocks they contain,” said NASA Associate Administrator Bhavya Lal at the International Astronautics Conference held. this week in Paris.

Scientists expect to be surprised by the test results. Hera’s principal investigator, Patrick Michel, attributes it to “ignorance that surrounds everything” about these celestial bodies. “It’s a new world we’re going to discover,” he says.

The asterophysicist considers asteroids “not only useless rocks in space, but rather surprising and complex small geological worlds, containing craters, rocky fields and shells of particles …”.

However, the scientific community has difficulty understanding these places because the gravity on their surface is very weak compared to Earth’s gravity, and therefore the interaction of matter in them “is never intuitive and we cannot rely on images to know how they do it. the asteroids interact, so they should also be reached, “explains Patrick. Michel.

For example, a small explosion near the surface of the asteroid Ryugu (discovered in 1999) created a crater 15 meters deep, much larger than previously predicted by simulations. While the rocks were expected to be solid, “the surface reacted like a liquid when it exploded, isn’t that surprising?” Says Michel.

Binary systems such as Didymos and its moon Demorphos account for about 15% of the known asteroids that have yet to be discovered.

With a diameter of 160 meters (the size of the largest pyramid among the pyramids of Giza), Demorphos will be the smallest asteroid ever studied.

The instruments of the Hera probe are expected to reveal the secrets surrounding Demorphos, from its shape, size and chemical composition, to its internal structure, to the degree of impact resistance and to the shape of the crater that will create the Dart spacecraft. At the end of the mission, a small satellite will land on its surface to monitor how it returns to its normal state.

This unprecedented documentation will help astrophysicists go back in time because asteroids are “excellent devices for revealing the history of the solar system,” according to Patrick Michel. These small rocky bodies have preserved information on the composition of the system and its planets formed by collisions.

“We live today in an age where all solid surfaces in the solar system contain craters,” says Michel. “To develop a scenario for their formation, we need to understand what happens when two objects collide.” And we will not arrive at this knowledge in the laboratory, but in reality thanks to the duo Dart and Hera, the scientists are hoping.

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