Hera: the European Space Agency ready to defend Earth against asteroids

The Solar System is not as peaceful as we would like to believe. On astronomical time scales, chaos even reigns in space. And looking closer, our planet receives between 10 and 100 tons of space material per day. Fortunately, the vast majority are just dust or small meteorites less than a few meters in size when they enter our atmosphere.

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Every five years, a meteorite releasing the energy of 30 Hiroshima bombs enters the atmosphere

That said, even ten meters upon entry can do a lot of damage. Residents of Chelyabinsk in Russia still remember the approximately 15 m superbolide which penetrated the atmosphere on February 15, 2013, and injured around 1,000 people (mostly due to shards of glass created by the shock wave). ). The object's speed was about 19 km/s before it was greatly slowed by its air resistance and ignited, becoming a fireball at 20 km altitude. Here are the impressive images from this event:

And that's for a very small object that no one saw coming… However, the total energy of this episode (atmospheric entry + explosion) is estimated at 30 times the Hiroshima atomic bomb. Such an event occurs every five years on average, but the more the size of the asteroid increases, the rarer the episodes. Thus, for an asteroid 700 m in diameter such as Didymos, the rate of occurrence of such an impact is approximately every 60,000 years, with obviously catastrophic consequences for an entire region.

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Planetary defense is a major issue for states and space agencies

With a view to preparing planetary defense against major threats from the sky, NASA sent its DART probe in 2022 to impact Dimorphos, a mini-moon of the asteroid Didymos, in order to assess potential changes in the couple's trajectory. . It is now the European Space Agency (ESA) which will provide “after-sales service” by analyzing “the method of deflecting an asteroid by an impactor implemented by the American DART mission”. This is where the Hera probe comes into play…

Hera will be able to study the internal structure of an asteroid for the very first time

This 1081 kg space probe will measure the size of the crater formed by the DART impact and will thus be able to study the interior of an asteroid for the first time. The mass of the small moon Dimorphos will be estimated with greater precision, a major challenge in understanding exactly how to deflect such objects. Hera will thus make it possible to create new guidance software for this type of mission and will at the same time release two small satellites (called CubeSat) Milani and Juventas: one will go into orbit around Dimorphos and the other will land on it . Dust, structure, porosity and its gravity field will thus be studied very closely.

Hera successfully took off aboard a SpaceX Falcon 9 on October 7. She now has two years of travel before reaching her target in December 2026, and thus helping Humanity protect itself from potential danger! The dinosaurs were not so lucky…

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