Deep Impact - We Now Have the Technology to Avoid It

We all want a future Earth fit for our children, and as a species we've become aware over the last few decades exactly how fragile our planet actually is. We've realised the devastation that could be caused by a super volcano, an asteroid impact, earthquakes, coronal mass ejections from our local star, a gamma ray burst aligned at our planet, plus our own self-inflicted damage to our environment in the form of climate change, pollution, damage to the marine ecosystem and ozone layer damage caused by chlorofluorocarbons.

A unique feature of homo sapiens amongst the other animals with whom we share the Earth is our ability not just to adapt to the environment, but actually change it. Indeed we've changed it - but adversely when it comes to ozone depletion, pollution and climate change, and indeed we're now making inroads in reversing our negative impact. However, all of these things are 'walks in the park' compared to the other threats, with one big exception - asteroid impacts.

We live in a cosmic shooting gallery. Anyone who disagrees should look no further than Comet Shoemaker-Levy 9, ripped apart by Jupiter's gravity and pummelling into the mighty gas giant in July, 1994. If that collision had occurred on Earth, none of us would be here now.

However, the Earth is not immune and collisions with both asteroids and comets have happened in our planet's past, and will happen again. The last time a civilisation-destroying asteroid 10kms across hit our terrestrial bulls eye was 65 million years ago at Chicxulub on the Yucatan Peninsular. Luckily, there was no civilisation about to destroy, but it was a bad day for T Rex and its dinosaur cousins, along with 80% of the plant and animal species on the planet. The death of the dinosaurs resulting at least partially from the impact on the Yucatan had the benefit of allowing small mammals and ultimately us to exploit the ecological niches vacated by these most successful of animals (in terms of the longevity of their reign).

At the same time though, it's a sobering thought to think that mass extinctions caused by incoming asteroids occur, on average, every 100 million years, and the next one will wipe out mankind. It's not a question of if, it's a question of when it will happen. Unlike T Rex though, the good news is that we can avoid such an unpleasant visitor from space, even with our present technology. Or rather we can ensure that such a potential impactor avoids us.

Worldwide, apart from the United States and NASA, most governments have not taken the issue of asteroid impacts seriously enough. Commendably NASA has surveyed large parts of the solar system, especially in the vicinity of Earth for Near Earth Objects (NEOs) and Potentially Hazardous Asteroids (PHAs) (those which directly cross the Earth's orbit around the Sun). Such objects routinely pass between the Earth and the Moon, even between the Earth and some of our geo-stationary satellites. Full details of NEOs and PHAs discovered are available here: http://neo.jpl.nasa.gov/

So what can we do if an NEO or PHA is detected and has our name on it? If the asteroid is composed of a loose barely gravitationally-bound conglomerate of ice and rock the nuclear option of blowing it to smithereens with a detonation would replace one problem with a host of them, we would then face the prospect of many smaller fragments reigning down on the Earth causing probably as much destruction.

One of the most considered scientific methods of removing the threat once one of these killer inbound asteroids has been located is not a Bruce Willis-style detonation at all, but concerns using the pressure of sunlight.

Light is composed of particles called photons, and like any particles, photons from the Sun create pressure - albeit very little pressure. Focus the photons using mirrors into an intense beam, find the asteroid early enough, and only a miniscule change of the object's trajectory by photon pressure is required.

The Pasadena, California based Planetary Society (TPS), the largest public space interest group in the world, is now working with a team at the University of Glasgow in Scotland to study a new technique which uses this concentrated light to gently move an asteroid -- a project they call "Mirror Bees." The researchers in Scotland, under the leadership of Massimiliano Vasile, became interested in this approach when they discovered that Mirror Bees would work more quickly and effectively than every approach, apart from nuclear warheads (the problems with this option has already been discussed).

This new technique involves many small spacecraft -- each carrying a mirror -- swarming around a dangerous asteroid. The spacecraft could precisely tilt their mirrors to focus sunlight onto a tiny spot on the asteroid, vaporizing the rock and metal, and creating a jet plume of super-heated gases and debris. Alternatively, the satellites could contain powerful lasers pumped by sunlight, and the lasers could be used to vaporize the rock. The asteroid would become the fuel for its own rocket -- and slowly, the asteroid would move into a new trajectory.

Major questions still remain about this technique. For example, will the plume of superheated gases ejected from an asteroid dissipate, or will it block sunlight to the mirrors? Would the debris settle on the satellite mirrors? Can the asteroid's rotation be dealt with effectively? Will the gas plumes be enough to deflect the asteroid?

TPS is stepping in to fund a series of laboratory experiments to answer these and other questions. Vasile's group is working with Ian Watson and the laser lab of the University of Glasgow's Mechanical Engineering Department to devise some ingenious small-scale experiments. TPS will be funding equipment, supplies, and a graduate student dedicated to working on the experiments. Only through these types of studies, as well as additional theoretical research, can the details of this technique be worked out and understood. If it pans out, it will be a rapid, effective, and safe option to use against the asteroid that inevitably will come Earth's way.

It is comforting to know that this valuable research is being undertaken against one of the biggest threats against our civilisation. Until we start seriously colonising space the human race still has all its eggs in one basket here on Earth. It would be foolish and irresponsible to ignore the risk, to be able to do something about it and yet do nothing. T Rex had an excuse. With our intelligence and technology, we don't.

• tags:
• NearEarthObjects
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• PlanetaryScience
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• DeepImpact
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• NASA
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• MirrorBees
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• PlanetarySociety

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