Tempus
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Tidskriften
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tidigare veckor: |
It
would be the end of the world as we know it. A relatively small
lump of rock a small asteroid, perhaps only a few hundred
metres across plunging to Earth would devastate a continent
or trigger tsunamis. Civilisation would be set back several centuries.
It is a real risk, say a group of astronauts and astronomers who
are to highlight the threat facing humanity by marking 30 June
as Asteroid Day. Supporters include Martin Rees, the astronomer
royal; guitarist Brian May; biologist Richard Dawkins; Apollo
9 astronaut Rusty Schweickart; Nobel laureate Sir Harold Kroto;
British astronaut Helen Sharman; and cosmonaut Alexey Leonov.
Their aim is to highlight the dangers facing Earth and to help
raise funds to build satellites to track deadly asteroids that
may be lurking in near-Earth space.
The
chosen date marks the anniversary of the Tunguska event,
when a small asteroid or comet exploded above Siberia with the
force of 1,000 atomic bombs. The largest impact event on Earth
in recorded history, it occurred on 30 June 1908.
Asteroid impacts are one of the few threats we can quantify,
Lord Rees said. Every 10 million years or so, a body a few
kilometres across will hit the Earth, causing global catastrophe
there are a few chances in a million that this is how we
will die. However, there are larger numbers of smaller asteroids
that could cause regional or local devastation. A body that is,
say, 300 metres across, if it fell into the Atlantic, would produce
huge tsunamis that would devastate much of Europe as well as the
east coast of the US. And still smaller impacts are more frequent
like the one at Tunguska in 1908. [This has been
put at between 60 and 190 metres across.]
The question is: can we be forewarned? The answer is yes. The B612 Foundation set up by former astronauts Ed Lu and Schweickart, and named after the asteroid home of the eponymous hero of Antoine de Saint-Exupérys The Little Prince has been promoting planetary defence since 2002. It is now attempting to raise $250m (£161m) to launch the Sentinel telescope, an orbiting observatory. Asteroid Day has been set up, in part, to help raise awareness of the issues involved.
The
Sentinel telescope would be launched on a Falcon 9 Space X rocket
and would hover in space relatively close to the sun, said
Diane Murphy, of the Asteroid Day project. It would then
look back out into space and survey asteroids and meteorites that
approach the Earth.
Crucially, Sentinel would be fitted with an infra-red telescope.
Asteroids are generally charcoal black and difficult to
spot in space, added Murphy. However, an infra-red
telescope would allow it to detect asteroids from their heat.
In this way, even very small asteroids no bigger than 50 metres
across could be tracked. Action could be taken to evacuate
the most vulnerable areas, added Rees. Even better
news is that during this century we could develop the technology
to protect us. A nudge, imparted a few years before
the threatened impact, would only need to change an asteroids
velocity by a millimetre per second in order to deflect its path
away from the Earth.
The finances work out, added Rees. The cost of an impact would be colossal, which means if you calculate an insurance premium in the usual way by multiplying probability by consequences, it turns out to be worth spending $1bn a year to reduce asteroid risk. Thats why I support Asteroid Day.
Events are planned for the day in several cities, including San Francisco and London, with top billing going to the first screening of the film 51º North at the Science Museum in London before it opens in cinemas across the UK later that week. Directed by Grigorij Richters, who helped to found Asteroid Day, 51º North follows film blogger Damon Miller, who unwittingly discovers that an asteroid is on course to crash on London. The soundtrack has been composed by May, a strategic adviser to the B612 Foundation.
The more we learn about asteroid impacts, the clearer it becomes that the human race has been living on borrowed time, said May. We are currently aware of less than 1% of objects comparable to the one that impacted at Tunguska, and nobody knows when the next big one will hit. And it takes just one.