Search for deadly asteroids must be accelerated to protect Earth, say experts

The search for deadly asteroids that could slam into Earth must be speeded up 100-fold to help protect the future of life on Earth, according to an influential group of scientists, astronauts and rock stars.

The call for action comes as experts around the world take part in Asteroid Day, an event on Tuesday marked by a series of talks and debates aimed at raising awareness of the existential threat posed by hurtling rocks from the heavens.

Lord Rees, the astronomer royal, and Brian May, from the rock group Queen, added their names to the 100X declaration, which calls for a rapid acceleration in human efforts to find and track potentially dangerous asteroids. Other signatories including Peter Gabriel, Richard Dawkins, Brian Cox and Eileen Collins, the first female commander of Nasa’s space shuttle.

“The aim is to ramp up public awareness and the awareness of governments to the fact that we are under threat from a meteor strike,” May told the Guardian. “It’s been made light of, and we’ve seen some great films, like Bruce Willis saving the day, but it is a very serious threat.”

Asteroid Day falls on the anniversary of an asteroid strike in 1908 that saw a 40 metre-wide lump of space rock enter the atmosphere over Tunguska in Siberia at about 33,500 miles per hour. The rock exploded mid-air and released the energy of a large hydrogen bomb, which flattened 2000 sq km of conifer forest.

Were an asteroid of the same size to slam into the atmosphere over London, the blast could destroy much of the capital within the M25. People in cities as far away as Oxford could be burned by the intense heat released in the explosion. In Scotland, the same blast would still have the force to blow peoples’ hats off.

From observations with ground-based telescopes, researchers know that of the million or so asteroids that could one day strike Earth, only about 10,000 are known and tracked. That means we are in the dark about 99% of the asteroids that have the potential to crash into the planet.

“They are clearly a threat and for the first time it is possible for us to do something to reduce that threat,” Lord Rees told the Guardian.

“It is now feasible to do a survey of all the potentially Earth-crossing asteroids above 50m in diameter, and objects like that impact Earth about once per century. One could then check their orbits to see if any are on a collision course with Earth and within 20-30 years have technology to divert any that are on course,” he added.

Huge asteroids several kilometres across are expected to hit Earth every ten million years or so. These can cause destruction on a global scale. A ten kilometre-wide space rock that crashed into what is now Mexico triggered a global catastrophe 68 million years ago which brought the reign of the dinosaurs to an end.

Since most of the Earth’s surface is covered by water, asteroids are more likely to arrive over the oceans. But these can be the worst impact sites for asteroids of about 300 metres wide. If one landed in the mid-Atlantic, it would produce a tsunami wave that could devastate cities on the east coast of the US, and along the coast of Europe.

“We know the rough numbers, we just don’t know when a particular asteroid is going to hit. If we are going to take precautions, we need to know the orbits of all of these bodies,” Rees said.

“The first thing is to do the survey to find out if there are any asteroids which seem to be on course with a high probability of hitting within the next 50 years. If we knew there was one on course to hit the Earth in next 50 years, that would focus minds on the technology.”

One mission, proposed by Nasa, aims to catalogue two thirds of the asteroids and other “near earth objects” that are larger than 140m and come close to Earth’s orbit. The NEOCam mission would use an infra-red camera to garner information on asteroid size, shape, rotation and composition. A private mission called Sentinel, which would put an another infra-red telescope in space, is being led by Ed Lu, a former space shuttle astronaut.

Scientists are actively looking at ways to protect Earth from any asteroids that do turn out to be on a collision course. One strategy is to crash a massive spacecraft into the asteroid and change its trajectory. Another option is a “gravity tractor”. In this scenario, a spacecraft flies alongside an inbound asteroid for long enough that its minuscule gravitational tug diverts the asteroid enough to pass Earth safely. Both could run into problems in a real situation, though: if the nudge does not work as expected, the asteroid may miss one city only to hit another.

The option to lob nuclear warheads at an incoming asteroid is appealing to Hollywood, but less so to many scientists, including May, who has a PhD in astrophysics.

“Blowing it up is probably not the greatest option, because you have a lot of fragments to deal with then, and it becomes rather random, but deflecting it one way or another seems to be an option,” he said.

“It’s absolutely possible there’s something out there of the magnitude that would wipe out a major city of the world, and that’s a very big thing: you’re talking about a human disaster on a vast scale.

“This is about saving us all. All the people on the planet, all the creatures on the planet, everything which we have built up and might be proud of. It’s a kind of insurance if you like,” he said.