Type of average speed and of accuracy: 292 words/22 minutes/wrong: 3 words
‘Evil’ asteroid hurtles toward Earth
There is very little time left to decide how to deal with the 390m wide rock that could crash into the plant
In a ancient Egypt, Apophis was the spirit of evil and destruction, a demon that was determind to plunge the word into eternal darkness.
A fitting name, astronomers reasoned, for a menace now hurtling toward Earth from outer space. Scientists are monitoring the progress of a 390m wide asteroid discovered last year that is protentially on a collision course with the planet and are imploring governments to decide on a strategy for dealing with it.
NASA has estimated that an impact from Apophis, which has an outside chance of hitting the Earth in 2036, would release more than 100,000 times the energy released in the unclear blast over Hiroshima. Thousands of square kilometers would be directly affected by the blast, but the whole of the Earth would see the effects of the dust released into the asmosphere.
And, scientists insist, there is acturally very little time left to decide. At a recent meeting of experts in near-Earth objects( NEO) in London,scientists said it could take decades to design, test and build the required technology to deflect the asteroid.
"It’s a question of when, not if, a near-Earth object collides with Earth," said Monica Grady, an expert in meteorites at UK’s Open University.
"Many of the smaller objects break up when they reach the Earth’s atmosphere and no impact. However, a NEO larger than 1km [wide] will collide with the Earth every few 100,000 years and a NEO larger than 6km, which could cause mass extinction, will collide with the Earth every 100 million years. We are overdue for a big one," she said.
Apophis had been intermittently tracked since its discovery inJune last year, but last December it started causing serious concern.
Projecting the orbit of the asteroid into the future, astronomers had calculated that the odds of it hitting the Earth in 2029 were alarming. As more observations came in, the odds got higher.
Having more than 20 years warning of protential impact might seem plenty of time. But, at the last week’s meeting, Andrea Carusi, president of the Spaceguard Foundation, said that the time for governments to make decisions on what to do was now, to give scientists time to prepare mitigation missions.
At the peak of concern, Apophis asteroid was placed at four out of 10 of threat posed by an NEOwhere 10 is a certain collision which could cause a global catastrophe. This was the highest of any asteroid in recorded historyand it had 1 in 37 chance of hitting the Earth.
The threat of a collision in 2029 was eventually rule out at the end of last year.
"When it does pass close to as in April 13, 2029, the Earth will deflect "it and change its orbit," said Alan Fitzsimmons, an astronomer from Queen’s University Belfast.
"There’s a small possibility that if it passes through a particular point in space, the so-called keyhole, … the Earth’s gravity will change things so that when it comes back around again in 2036, it will collide with us," he said.
The chance of Apophis passing through the keyhole, a 600m patch of space, is 1-in-5,500 based on current information.
There is no shortage of ideas on hoe to deflect asteroids. The Advanced Concepts Team at the European Spaces Agency ( ESA) have led the effort in designing a range of satellites and rockets to nudge asteroids on a collision courage for Earth into a different orbit.
No technology has been left unconsidered, even protentially dangerous idea such as nuclear powered spacecraft.
"The advantage of unclear propulsion is a lot of power," Fitzsimmons said.
"The negative thing is that … we haven’t done it yet. Whereas with solar electric propulsion, there are several spacecraft now that do use this technology, so we’re fairly confident it would work," he said.
The favored method is also potentially the easiest – throwing a spacecraft at an asteroid to change its direction. The ESA plans to test this idea with its Don Quixote mission, where two satellites will be sent an asteroid. One of them, Hidalgo, will collide with the asteroid at high speed while the other, Sancho, will measure the change in the object’s orbit.
Decissions o the actual design of these probe will be made in the coming month, with launch expected some time in the next decade. One idea that seems to have no support from astronomers is the use of explosives.
"If you explose too close to impact, you’ll get hit by several fragments rather than one, so you spread out the area of damage," Fitzsimmons said.
In September, scientists at Strathclyde and Glasgow universities began computer the simulations to work out feasibility of changing the directions of asteroids on a collission curse for Earth. In spring next yea, there will be another opportunity for radar observations of Apophis that will help astronomers work out possible orbits of asteroid more accurately.
If, at the stage, they can’t rule out an impact with Earth in 2036, the next chance to make better observations will not be until 2013. NASA has argue that a final decision on what to do about Apophis will have to made at that stage.
"It may be a decision in 2013 whether or not to go ahead with a full-blown mitigation mission, but we need to start planning it before 2036," Fitzsimmons said.
In 2029, astronomers will know for sure if Apophis will pose a threat in 2036. If the worst-case scenarios turn out to be true and the Earth is not prepared, it will be too late.