The Earth has already suffered major asteroid impacts and others are possible. But, as shown in Asteroid Hunters 3D, the new IMAX film at Cité de l’espace, a real focus on planetary defence has been initiated.

A large-sized object is heading towards Earth and threatening the survival of mankind: several films have been made using this disaster scenario, whether it is the classic When Worlds Collide in 1951, (that one was about a whole other planet!) or the more recent Deep Impact and Armageddon (both 1998).
Credibility was hardly the strong point of these films. However, an important development can be seen. While the first envisaged a Noah’s Ark principle to save only a few representatives of our species, the other two developed the idea of an international effort to prevent the threat. Now, it is indeed such an effort (less Hollywood, but more realistic) which has been under construction for years.


The Earth has experienced several asteroid impacts, some cataclysmic like the one which disrupted its ecosystem to the point of causing the extinction of the dinosaurs (we are simplifying slightly here). In Arizona, the famous Meteor Crater, 1.2 km wide and 190 m deep, is evidence of the arrival at this location of a meteorite of around 50 m in diameter 50,000 years ago. It is estimated that the resulting disaster wiped out any life form within a radius of 4 km and led to considerable destruction up to around 20 kilometres away.

Le Meteor Crater en Arizona. La «cicatrice» de 1,2 km de large de l’impact d’un astéroïde d’environ 50 m de diamètre. Crédit : USGS via NASA

Meteor Crater in Arizona. The 1.2 km wide “scar” of the impact of an asteroid with a diameter of around 50 m.
Credit: USGS via NASA

Nowadays, such an impact would level a city. Moreover, asteroids of several tens of metres, potentially capable of such damage, are called “City Killers,” and are one of the new dangers taken into account by specialists in the “wandering rocks” of the Solar System. Indeed, it is thought that we have listed almost all objects more than a kilometre wide which could cause the greatest disasters. Now, they are busying themselves with smaller threats, which could cause disasters at regional levels. This search to monitor the sky and protect us is the central subject of Asteroid Hunters 3D (trailer in English below, the film is translated into French at Cité de l’espace).

At Cité de l’espace in Toulouse, this 38-minute documentary, directed by W.D. Hogan, benefits from an all-new IMAX 3D theatre equipped with a 400m2 screen. Special measures have been implemented so that spectators can wear the essential 3‑D glasses, while respecting the necessary health requirements.

The subject could, at first glance, seem worrying. However, Asteroid Hunters 3D, shows more than anything that, around the world, scientists are studying these objects from observatories or thanks to space missions. The planetary defence focus thus established, first of all, consists in having the means to detect those which are on a collision course. Such automatic monitoring telescopes already exist and they are being reinforced with more effective instruments. The next stage would be to deflect a dangerous asteroid by organising a special space mission (various concepts are under consideration). It should be noted that probes have repeatedly been sent to asteroids so we can better understand their nature, which obviously will be essential to choose the best methods to deflect them.


One possible method relies on a deliberate impact by a spaceship. To effectively assess the merits of such a strategy, NASA and the European Space Agency (ESA) are working with AIDA (Asteroid Impact & Deflection Assessment). In July 2021, the American DART probe (Double Asteroid Redirect Test) will take off heading for the 780 m wide asteroid, Didymos. In September 2022, DART will crash into Dimorphos, Didymos’s little 160 m-wide Moon.

Illustration du concept de la mission DART de la NASA. Crédit : NASA

Illustration of the concept of NASA’s DART mission.
Credit: NASA

After this collision, the ESA’s Hera probe enters the scene. It will take off in October 2024 to reach Didymos and Dimorphos in late 2026. Hera will examine the impact crater left by DART, which will provide scientists with a huge amount of information about the nature of such celestial bodies. Above all, the European probe will determine precisely how Dimorphos’s orbit around Didymos has been affected by the impact of DART. Such surveys will allow us to calculate how we could in the future deflect effectively and safely, if we have to, an asteroid heading towards Earth.

Illustration montrant Hera scrutant le cratère laissé par l’impact de DART sur Dimorphos. Crédit : ESA

Illustration showing Hera scanning the crater left by the impact of DART on Dimorphos.
Credit: ESA

And to find out more, we suggest the recording of The Day of the Asteroids below, an ESA production from June 2020.
This programme, led by Bruce Benamran, features the following expert guests:  Ian Carnelli (ESA), Aurélie Moussi (CNES), Patrick Michel (CNRS – Centre National de la Recherche Scientifique), Naomi Murdoch (ISAE-Supaero), Marc Serres (Luxembourg Space Agency) and ESA astronaut, Léopold Eyharts.




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