Forget wars, global warming, etc. - Here's some really bad, potentially fatal news...

It's called Apophis. It's 390m wide. And it could hit Earth in 31
years time

· Scientists call for plans to change asteroid's path
· Developing technology could take decades

Alok Jha
Wednesday December 7, 2005
The Guardian


In Egyptian myth, Apophis was the ancient spirit of evil and
destruction, a demon that was determined to plunge the world into
eternal darkness.
A fitting name, astronomers reasoned, for a menace now hurtling
towards Earth from outerspace. Scientists are monitoring the progress
of a 390-metre wide asteroid discovered last year that is potentially
on a collision course with the planet, and are imploring governments
to decide on a strategy for dealing with it.


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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 nuclear blast over Hiroshima.
Thousands of square kilometres would be directly affected by the blast
but the whole of the Earth would see the effects of the dust released
into the atmosphere.
And, scientists insist, there is actually very little time left to
decide. At a recent meeting of experts in near-Earth objects (NEOs) in
London, scientists said it could take decades to design, test and
build the required technology to deflect the asteroid. Monica Grady,
an expert in meteorites at the Open University, said: "It's a question
of when, not if, a near Earth object collides with Earth. Many of the
smaller objects break up when they reach the Earth's atmosphere and
have no impact. However, a NEO larger than 1km [wide] will collide
with Earth every few hundred thousand years and a NEO larger than 6km,
which could cause mass extinction, will collide with Earth every
hundred million years. We are overdue for a big one."

Apophis had been intermittently tracked since its discovery in June
last year but, in 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 potential impact might seem
plenty of time. But, at 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 on the Torino scale - a measure of the
threat posed by an NEO where 10 is a certain collision which could
cause a global catastrophe. This was the highest of any asteroid in
recorded history and it had a 1 in 37 chance of hitting the Earth. The
threat of a collision in 2029 was eventually ruled out at the end of
last year.

Alan Fitzsimmons, an astronomer from Queen's University Belfast, said:
"When it does pass close to us on April 13 2029, the Earth will
deflect it and change its orbit. 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." The chance of Apophis
passing through the keyhole, a 600-metre patch of space, is 1 in 5,500
based on current information.

There are no shortage of ideas on how to deflect asteroids. The
Advanced Concepts Team at the European Space Agency have led the
effort in designing a range of satellites and rockets to nudge
asteroids on a collision course for Earth into a different orbit.

No technology has been left unconsidered, even potentially dangerous
ideas such as nuclear powered spacecraft. "The advantage of nuclear
propulsion is a lot of power," said Prof Fitzsimmons. "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."

The favoured method is also potentially the easiest - throwing a
spacecraft at an asteroid to change its direction. Esa plans to test
this idea with its Don Quixote mission, where two satellites will be
sent to 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. Decisions on the actual design of these
probes will be made in the coming months, with launch expected some
time in the next decade. One idea that seems to have no support from
astronomers is the use of explosives.

Prof Fitzsimmons. "If you explode too close to impact, perhaps you'll
get hit by several fragments rather than one, so you spread out the
area of damage."

In September, scientists at Strathclyde and Glasgow universities began
computer simulations to work out the feasibility of changing the
directions of asteroids on a collision course for Earth. In spring
next year, there will be another opportunity for radar observations of
Apophis that will help astronomers work out possible future orbits of
the asteroid more accurately.

If, at that stage, they cannot rule out an impact with Earth in 2036,
the next chance to make better observations will not be until 2013.
Nasa has argued that a final decision on what to do about Apophis will
have to be 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
2013," said Prof Fitzsimmons. 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. "If we wait until 2029, it would seem unlikely that you'd be
able to do anything about 2036," said Mr Yates.


MacP
"Mur a bi i gun tarrag, 's ann LEAMSA!"
"If she ain't nailed down, she's MINE!"

.

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