Hunt on for killer asteroids
2006-08-18 12:36
Prague, Czech Republic - Astronomers are stepping up the global effort to scan the skies for "near-Earth objects": asteroids and comets on a collision course with the planet and big enough to pack a deadly punch.
The International Astronomical Union said on Thursday it has set up a special task force to broaden and sharpen its focus on impact threats.
Experts say there are an estimated 1 100 known objects that are one kilometre or wider across - large enough to not only take out a European country but threaten the entire world.
"The goal is to discover these killer asteroids before they discover us," said Nick Kaiser of the University of Hawaii, whose Pan-Starrs programme will train four powerful digital cameras on the heavens to watch for would-be intruders.
Nasa's Spaceguard Survey, which already has identified 800 of the larger objects and has 103 on an impact risk watchlist, wants to find 90% by the end of 2008.
The US Congress has asked the space agency for a plan to comb the cosmos for faint objects and log their position, speed and course by 2020.
Astronomers will have their work cut out for them. Experts say there are about 100 000 such objects hidden among the haze of stars, and as many as one million half that size.
One known as the Tunguska object slammed into remote central Siberia in 1908, unleashing energy equivalent to a 15-megaton nuclear bomb that wiped out 60 million trees over a 2 150-square-kilometre area. Had it hit a populated area, the loss of life would have been staggering.
'Who ya gonna call?'
Giovanni Valsecchi of Italy's National Institute of Astrophysics said the ultimate aim is a permanent warning system like those that now monitor the Pacific for tsunamis.
The idea: Give the world enough lead time to come up with a workable response to a confirmed threat.
"Right now, unfortunately, there are no 'asteroid busters' or hotlines. Who ya gonna call?" said Andrea Milani Comparetti, a professor of mathematics at the University of Pisa.
Although close encounters are unnerving, they give astronomers a unique opportunity to get a better glimpse of asteroids and comets, the leftover building materials of the universe, and gain a better understanding of the origins of the solar system.
But widening the search for threatening objects creates a problem: Discoveries of potential threats could become commonplace, either creating unnecessary panic and confusion or lulling the public into a false sense of complacency.
"We're now going to be finding such objects once a week instead of once a year," said David Morrison, a Nasa scientist who will chair the new IAU task force on impact threats.
Ultimately, Valsecchi conceded, mankind may not be able to dodge every cosmic bullet. Earth's craters bear silent witness to what can happen.
"It's through collisions that planets are born," he said, "and through collisions that planets die."
On the net:
www.iau.org
pan-starrs.org
- AP