Scientists plead for cash to repel asteroids

Scientists have urged governments to fund a mission to find out if an asteroid could be nudged off its trajectory to avoid a collision with Earth.

The European Space Agency (ESA) has teamed up with Nasa for the first planetary defence operation, which aims to study the effect of crashing into a small rock dubbed ‘‘Didymoon’’ orbiting an asteroid called Didymos A.

The Aida mission, which stands for Asteroid Impact & Deflection Assessment, is made up of Nasa’s Double Asteroid Redirection Test (Dart) spacecraft, which will smash into the little satellite, and the ESA’s Hera craft which will then study the impact.

But it needs the agreement of ministers meeting in Seville later this month to decide on future funding projects.

A group of 1200 scientists, including Lord Rees, the Astronomer Royal, have written to ministers warning of the danger of not funding the mission. They say: ‘‘Unlike other natural disasters, an asteroid impact with Earth is not only one we know how to predict, but one we can prevent, by means that just need to be tested. Today, we are the first generation of humans who have the necessary technology to try to change the trajectory of an asteroid.

‘‘We urge governments to keep the Hera mission high on the agenda, providing vital knowledge to protect ourselves and future generations.’’

Asteroids are leftover matter from the formation of planets and range in size from a few feet to tens of kilometres. They orbit the Sun, and sometimes come dangerously close to Earth, yet currently there is nothing that can be done to deflect an incoming threat.

There are tens of millions of asteroids larger than 10m that would have an energy larger than a small nuclear weapon if they entered the Earth’s atmosphere. So far, scientists have identified 21,443, which is fewer than 20 per cent of the total. ‘‘New asteroids are being discovered at the rate of some four per day’’, said Dr Patrick Michel, Aida/Hera principal investigator, who is based at the Cote d’Azur Observatory in Nice. ‘‘We need a co-ordinated international strategy for nearEarth object impact mitigation. The Aida collaboration will give us the possibility to test our capabilities to deflect an asteroid.’’

Nasa’s Dart mission is due to launch within a year, arriving at the binary asteroid system in 2022, where it will immediately crash into the 160m-wide Didymos B (Didymoon), which is circling the 800m-wide Didymos A.

The system orbits the Sun every 771 days and is classed as a potentially hazardous asteroid to Earth

The team hopes the impact will change the orbit around Didymos, the first time any body in space would have been moved by humans. Hera would arrive in January 2027 carrying instruments to measure the impact crater.