Chelyabinsk, a decade later: can we detect asteroids coming from the direction of the Sun?

No one saw the Chelyabinsk meteor coming on February 15, 2013, the largest asteroid to hit Earth in more than a century. Just after dawn on a sunny winter day, a 20-meter, 13,000-ton asteroid smashed into the atmosphere over the Ural Mountains in Russia at a speed of more than 18 km/s.

The relatively small rock exploded in the atmosphere at an altitude of 30 kilometers, releasing about half a megaton of energy (equivalent to 35 bombs with the power of the atomic bomb that exploded in Hiroshima). Two minutes later, the shock wave reached the ground, damaging thousands of buildings, breaking windows and injuring around 1,500 people from flying glass fragments.

Hidden in the glow of our Sun are an unknown number of asteroids with trajectories of which we are unaware. Quite a few of those asteroids could be heading for Earth.

“There are asteroids the size of the Chelyabinsk meteorite that hit Earth roughly every 50-100 years,” explains Richard Moissl, Head of Planetary Defense at the European Space Agency (ESA).

“Injuries from airborne explosions or similar events could be prevented if people were informed of an impending impact and its expected effects. With prior warning, local authorities may advise people to stay away from windows and glass.”

NEOMIR will act as an early warning system to detect and monitor any asteroid heading towards Earth from the direction of the Sun. NEOMIR will be positioned between the Sun and the Earth, at the L1 Lagrange point. Using a highly sensitive infrared detector, it will pick up near-Earth-passing objects that are more than 20 meters in diameter, and will do so at least three weeks before their potential collision with Earth. (Illustration: ESA / Pierre Carril)

Moissl adds: “ESA’s upcoming NEOMIR mission will detect asteroids such as Chelyabinsk coming from the daytime region of the sky, greatly improving our current capabilities to predict and plan for dangerous impacts.”

Of course, there is also the risk of an even larger asteroid hitting Earth from the illuminated side. Such a scenario is less likely, since the larger the asteroid, the fewer the number of such bodies in the solar system and the easier they are to detect. In fact, almost all asteroids larger than 1 kilometer have already been discovered.

But as the dinosaurs would tell us, if they could, the damage caused by a huge asteroid impact is unimaginable. Fortunately, as the impact of NASA’s DART probe has shown, and as ESA’s Hera mission will investigate in detail, we can deflect such an asteroid.

So how can we know for sure that we are prepared? ESA’s next NEOMIR mission will be located at the L1 Lagrange point between Earth and the Sun. Undisturbed by Earth’s atmosphere, its infrared telescope will be able to detect asteroids 20 meters and larger currently lurking under the sunlight.

Knowing well in advance, an asteroid impact is the only natural disaster we can avoid. (Source: ESA)