Wanted:
man to land on killer asteroid and gently nudge it from path to
Earth
· Nasa evokes Hollywood in effort to avoid catastrophe
· Mission would bridge gap between moon and Mars
David Adam
Friday November 17, 2006
The Guardian
It is the stuff of nightmares and, until now, Hollywood thrillers.
A huge asteroid is on a catastrophic collision course with Earth
and mankind is poised to go the way of the dinosaurs.
To save the day, Nasa now plans to go where only Bruce Willis has
gone before. The US space agency is drawing up plans to land an
astronaut on an asteroid hurtling through space at more than 30,000
mph. It wants to know whether humans could master techniques needed
to deflect such a doomsday object when it is eventually identified.
The proposals are at an early stage, and a spacecraft needed just
to send an astronaut that far into space exists only on the drawing
board, but they are deadly serious. A smallish asteroid called
Apophis has already been identified as a possible threat to Earth
in 2036.
Chris McKay of the Nasa Johnson Space Centre in Houston told the
website Space.com: "There's a lot of public resonance with the
notion that Nasa ought to be doing something about killer asteroids
... to be able to send serious equipment to an asteroid.
"The public wants us to have mastered the problem of dealing with
asteroids. So being able to have astronauts go out there and sort
of poke one with a stick would be scientifically valuable as well
as demonstrate human capabilities."
A 1bn tonne asteroid just 1km across striking the Earth at a 45
degree angle could generate the equivalent of a 50,000 megatonne
thermonuclear explosion. Attempting to break it up with an atomic
warhead might only generate thousands of smaller objects on a
similar course, which could have time to reform. Scientists agree
the best approach, given enough warning, would be to gently nudge
the object into a safer orbit.
"A human mission to a near Earth asteroid would be scientifically
worthwhile," Dr McKay said. "There could be testing of various
approaches. We don't know enough about asteroids right now to know
the best strategy for mitigation."
Matt Genge, a space researcher at Imperial College, London, has
calculated that something with the mass, acceleration and thrust of
a small car could push an asteroid weighing a billion tonnes out of
the path of Earth in just 75 days.
Gianmarco Radice, an asteroid expert at Glasgow University, said
the best approach would be to land a device to dig into the object.
"You could place something on the surface to eject material that
would push the asteroid in the other direction."
Mirrors, lights and even paint could change the way the object
absorbed light and heat enough to shift its direction over 20 years
or so. With less notice, mankind could be forced to take more
drastic measures, such as setting off a massive explosion on or
near the object to change its course. In 2005, Nasa's Deep Impact
mission tested a different technique when it placed an object into
the path of a comet.
Dr Radice said robots could do the job just as well, doing away
with the need for a risky and expensive manned mission. Last year
Japan showed with its Hayabusa probe that a remote spacecraft can
land on an asteroid.
But with manned missions to the moon and possibly Mars on its to-do
list again, Nasa is keen to extend the reach of its
astronauts.
Dan Durda, a senior research scientist in the Department of Space
Studies at the Southwest Research Institute in Boulder, Colorado
said an asteroid landing mission would be a good way test the new
Constellation programme spacecraft, the Apollo-style planned
replacements for the space shuttle with which Nasa hopes to return
to the moon.
He told Space.com: "A very natural, early extension of the
exploration capabilities of this new vehicle's architecture would
be a "quick-dash" near-Earth asteroid rendezvous mission."
Tom Jones, a former shuttle astronaut, said: "After a lunar visit,
we face a long interval in Earth-Moon space while we build up
experience and technology for a Mars mission. An asteroid mission
could take us immediately into deep space, sustaining programme
momentum, adding public excitement and reducing the risk of a later
Mars mission."
Europe has its own efforts to tackle asteroids. Its planned Don
Quijote mission will launch two robot spacecraft, one to tilt at a
harmless passing space rock, and a second to film the collision and
watch for any deviation in the asteroid's path.
'Not if, but when...' Hits and near misses
At Nasa's Jet Propulsion Laboratory, in California, scientists
monitor all "potentially hazardous asteroids" that might one day
end up on a collision course with Earth. So far they number 831.
The next close-ish shave - at a mere 17 times the distance from the
Sun to the Earth - will be asteroid 2004QD14 on November 29.
The Earth has a long history of asteroid strikes. Thirty five
million years ago, a 5km-wide asteroid ploughed into what is now
Chesapeake Bay, in the US, leaving an 80km crater. In 1908, an
asteroid devastated swaths of Siberia when it exploded mid-air with
the force of 1,000 Hiroshimas. The theory that the dinosaurs were
wiped out by a huge asteroid striking Mexico 65m years ago is
controversial since scientists uncovered rocks from the crater
predating the extinction of the dinosaurs by 300,000 years.
A near miss, when asteroid QW7 came within 4m km of Earth in
September 2000, led Liberal Democrat MP Lembit Opik to declare:
"It's not a case of if we will be hit, it is a question of when.
Each of us is 750 times more likely to be killed by an asteroid
than to win this weekend's lottery."
In January 2002, the former science minister, David Sainsbury,
announced the government's response to the threat from hurtling
asteroids: a new information centre based in Leicester.