- The Observer,
- Sunday May 28 2000
Armageddon - triggered by an asteroid hurtling into our planet - is a genuine risk. Now some scientists are pressing the European Space Agency (Esa) to construct a satellite called Gaia which could pinpoint errant chunks of rock that threaten Earth.
The probe - the most accurate telescope ever built - would track objects a kilometre or more in diameter, allowing scientists to predict their path years before their collision with our planet. Rocket-born nuclear bombs could then be launched to nudge them from their deadly paths.
'Gaia will carry a set of giant video cameras that will take colour, stereoscopic images of more than a billion stars, galaxies and other objects,' said one of the project's leaders, Dr Jerry Gilmore, of Cambridge's Institute of Astronomy.
'Essentially we are going to take a 3-D movie of the Milky Way. We will be able to construct a map of the heavens of such unsurpassed accuracy that we will be able to solve a host of major astronomical problems: the origin of the Milky Way, the shape of the universe - and the likelihood of Earth being battered by an asteroid.'
Earth's prospects of being destroyed by a large chunk of planetary masonry are currently being investigated by a government task force set up by Lord Sainsbury. The three-man team - made up of senior science administrator Harry Atkinson, environmentalist Sir Crispin Tickell and Professor David Williams of University College, London - will report in a few weeks.
The team believes there is a real risk, albeit a small one, that Earth will suffer a major asteroid impact, and that more international co-operation is needed to track the most dangerous objects. It has been calculated - by studying the rate at which lunar craters were formed by crashing meteorites and asteroids - that Earth will be struck by an object greater than a kilometre in diameter every 500,000 years.
Nasa recently established a Near Earth Object programme which has tracked 400 of the estimated 1,000 kilometre-plus asteroids in our part of the solar system. 'None are likely to strike our planet in the foreseeable future,' said Donald Yeomans, the programme's chief. 'However, there are hundreds out there that we just don't know about.'
Scientists say asteroids greater than a kilometre in diameter will cause global devastation. 'They will throw up vast clouds of dust that will blot out the sun, pour down acid rain, freeze the planet, and destroy all civilisations,' said Yeomans.
Nasa's survey programme is restricted to ground-based telescopes and radio observatories. Gaia's telescopes would detect an object the size of a shirt button on the Moon.
To achieve such precision the probe would have to have virtually no moving parts with every component maintained at a precise temperature to ensure no thermal buckling or movement.
Due to be launched by an Ariane 5 rocket in 2009, Gaia is short-listed for £350 million of Esa funding, but is in competition with a proposed probe to Mercury. Gaia is the favourite to gain approval in September.
'Gaia will carry out all sorts of different kinds of astronomy,' said Gilmore. 'However, the real bonus is that it could save us from the same fate as that suffered by the dinosaurs.'
Pinpointing an asteroid decades before it strikes Earth is one thing. Doing something about it is quite another. Blowing it up with a nuclear bomb - as Bruce Willis did in the film Armageddon - would do more damage than good, say scientists, for the blast would probably pepper Earth with cosmic shrapnel. 'However, nudging it off its trajectory with an A-bomb explosion, so that it missed us completely, might well work,' said Yeomans.
