On June 2, an asteroid appeared on scientists’ radars after unexpectedly entering the atmosphere. The rock came from the depths of the Solar System at a speed over 61,000 km/h, before exploding over a farm in South Africa. Would it have been possible for scientists to detect this asteroid before it came so close to us?

Growing awareness

Since 2013, space surveillance has been a major issue for agencies and government bodies. The Chelyabinsk meteor was the main reason for this new sense of awareness and the international efforts it sparked. At 19 meters wide, it is considered to be the largest meteorite ever to collide with the Earth since 1908. The explosion over Siberia on February 15, 2013 resulted in 1,600 people wounded, 5,000 housing units destroyed and a shock wave felt more than 90 km away.

Potentially dangerous asteroids, or near-Earth objects

How can such disasters happen when space agencies have their terrestrial and space telescopes glued to the sky? That’s because their devices focus on “potentially dangerous asteroids,” that is, those measuring more than 140 meters, NASA explains. Smaller celestial objects are very difficult to spot before they enter the earth’s atmosphere.

A universe full of the unknown

The International Astronomical Union estimates that it has discovered only 1% of asteroids measuring less than 140 meters. In 2016, about 15,000 near-Earth objects (NEOs) – that is, rocks over one kilometer wide – that could become hazards to the Earth were detected, a 50% increase in the number of known asteroids near the Earth since 2013. 95% of them had been discovered by NASA-funded investigations, mainly through its terrestrial telescopes. Each week, NASA locates approximately 30 new ones, which it reveals in an FAQ on its site. In addition, NASA’s Jet Propulsion Laboratory’s Center lists and updates asteroid discoveries in real time.

Are we at risk of a deadly collision?

NASA is clear: no asteroid is set to present a significant risk to Earth in the next hundred years. However, it does not exclude other impacts, such as that of Chelyabinsk in 2013. Experts believe that such an asteroid would impact the Earth once or twice a century. “However, given the current incompleteness of the NEO catalog, an unexpected impact – such as the Chelyabinsk event – could occur at any time,” a NASA statement read in August 2017.

Is there an astronaut in the vessel?

Since this isn’t a Bruce Willis movie, there hasn’t been a mission to divert an asteroid gravitating too close to Earth. However, technological advances have made it possible to imagine a way to deflect an asteroid and, as of 2016, NASA has conducted 3D digital simulations. In 2022, the AIDA (Asteroid Impact and Deflection Assessment) mission, led by NASA and ESA (European Space Agency), is expected to divert the trajectory of the Didymos asteroid discovered in 1996. It actually consists of a couple of asteroids rotating around each other. The mission would not blow it up, since that would create debris that could hit the Earth. Space agencies have imagined that a probe weighing several thousand kilos will collide with the smaller of the two asteroids when it is closer to Earth, at a distance of about 11 million kilometers.