Rocking our world?
Asteroids are unlikely to wipe us out - but they could help us to learn the secrets of the universe.
Asteroid 2002 NT7 – a two kilometre lump of rock floating through space – hit the headlines in late July 2002, when astronomers said there was a one in 75,000 chance that it could collide with the Earth in 2019.
Many experts quickly pointed out that one in 75,000 are pretty long odds, merely reflecting that we didn’t really know where the asteroid will be in 17 years’ time (1).
And already, further observations have pinned down the asteroid’s orbit, ruling out a collision in 2019. It is highly likely that a few more months of monitoring will eliminate the risk of collision further into the future (2).
2002 NT7 follows 2002 MN, which made the news just weeks earlier as it slipped between the Earth and the moon. There was concern that an asteroid strike could trigger nuclear war, among other catastrophes (3). Why has the threat of asteroids, comets, or ‘Near Earth Objects’ become such a big story?
Insurance company MunichRe included the threat of asteroids in its ‘natural hazards assessment’ for the first time this year. Previously, such events were considered ‘too improbable’ or ‘too catastrophic’ to be worthy of consideration – but that was ‘before the terrorist attack of 11 September’, says MunichRe, ‘which generally resulted in a radical reconsideration of loss potentials’.
It’s not that MunichRe thinks the chances of an impact are greater now than they were on 10 September 2001, just that we should all worry more. So asteroids move up the agenda.
The recent media attention may have given long-time asteroid worriers a chance to shine (‘I may sound like one of these guys who walks up and down with a sandwich board saying the end of the world is nigh, but the end is nigh’ said Liberal Democrat MP Lembit Opik (4)). But there was growing concern about asteroids within government circles long before 11 September.
In 2000, the UK government commissioned a report to look into the threat from space. While the report called for more science, the government was more enthusiastic about setting up a Near Earth Object Information Centre to provide a pre-emptive ‘response’ to public concern over the asteroid threat (5).
In the USA, the airforce has taken a keen interest. Simon P Worden, deputy director of Operations US Space Command, complains that people say to him: ‘General, if this threat only hits every 50million years, I think we can focus our attention on more immediate threats.’ But he has persistently raised the profile of the asteroid threat, with the US airforce funding the Lincoln Near Earth Asteroid Research (LINEAR) project, which discovered 2002 NT7 (6).
Part of the new interest in asteroids is driven by new science. We first realised that impacts from space were important in the geological history of the Earth when man landed on the moon. It took human exploration to confirm that the moon’s lunar craters are the product of impacts rather than volcanoes. In the absence of an atmosphere or plate tectonics to erode the evidence, the moon’s surface preserves evidence of past impacts.
In 1980, a group of scientists led by Nobel prize-winning physicist Luis Alvarez suggested that dinosaurs had been wiped out by an impact event – but there was no trace of the crater that would have been left by such a destructive collision. Then, in 1991, a vast crater buried under the Yucatán peninsular and the Gulf of Mexico was identified with the Alvarez impact, convincing many that the mystery of the dinosaurs’ demise had been solved – but also that humanity faced a previously unrecognised threat from space (7).
In the 1990s, electronic cameras were deployed by organisations such as the LINEAR project and NASA to find and track asteroids in large numbers. The new data allowed the first reasonably reliable estimates of the risk from Near Earth Objects – with claims that our chances of being killed by an asteroid are comparable to our chances of dying in an air accident. For most people that should be reassuring: after all, how long do you spend worrying about dying in a plane crash?
Yet it seems remarkable that the risk is so high. We know that people die in air crashes, but not in meteorite strikes. Should we be spending as much on telescopes as we do on air traffic control? The answer is that while air crashes kill relatively few people relatively often, Near Earth Objects can be expected to kill millions (or even billions) but very, very rarely. Counterintuitive as it seems, science is telling us the risk is real enough (8).
But new scientific understanding cannot explain the heightened consciousness of ‘asteroids as threat’. Consider the contrast between the media coverage of asteroids and the attitude of those familiar with the science. According to meteorite scientist Matthew Genge:
‘Here at the Meteoritical Society Meeting in Los Angeles…there has been much excitement at the news that asteroid 2002 NT7 may approach close to the Earth in 2019. Scientists involved in asteroid research have a very different view on such objects than most people. When an asteroid comes close to the Earth it gives us an opportunity to study it in more detail using Radar and there are one or two scientists here who expressed the hope that it passes close enough for us to mount a space mission to return a sample to Earth. Not one of the asteroid scientists present at the conference is worried that 2002 NT7 will collide with the Earth.’ (9)
The scientists’ positive outlook is the result of recent successes, like the landing of the spacecraft NEAR-Shoemaker on the asteroid Eros on 2001. But the response from politicians and policymakers to the new science on asteroids has been profoundly influenced by a broader culture of fear, which predisposes people to see threats rather than opportunities. Ironically, this excessive focus on risk could possibly lessen our capacity to deal with problems from space.
While we have learned a great deal about asteroids and comets, there is still much to learn before we could hope to manoeuvre them through space. To understand how a Near Earth Object would respond to a nuclear blast we need to understand its structure and composition. Such understanding will require more visits to such objects, and for us to become far better at getting into, and moving around, space.
But space exploration cannot and should not be justified in terms of seeking safety. Space is risky, and any programme that ventures into space seeking to escape risk will inevitably find itself crippled from the beginning, unable to take the bold decisions needed to make progress.
However, even as a risky endeavour, space exploration in general, and Near Earth Objects in particular, hold great promise – of insights into the origins of the solar system and, just possibly, the origins of life. In the more hazy future, there could be broader cultural benefits from space colonisation and tourism as humanity’s horizons are expanded – and ultimately there could be useful industrial activity in space, making use of microgravity for materials processing or mining asteroids for materials for construction in space.
Such all-round development would put us in a better position to deal with any threat that did arise. Unfortunately, our present approach is narrow-minded. US Congressman Dana Rohrabacher, chairman of the Space and Aeronautics Subcommittee of the House Science Committee, has seen a different sort of opportunity in the asteroid threat, proposing a tie-in between the ‘Star Wars’ missile defence and ‘planetary defence’ against asteroids (10).
The consequences of prioritising safety above all else are clear. Almost half of NASA’s supply of plutonium, used to power interplanetary spacecraft, has recently been ‘reassigned for use by an undisclosed national security agency’. Scaremongering about the threat of asteroids will only put off the day we have a chance to do something about it (11).
Risk, science and society, by Professor Sir Colin Berry
(1) Space rock ‘on collision course’, BBC News, 24 July 2002
(2) Asteroid to miss – this time around, BBC News, 29 July 2002
(3) Space rock’s close approach, BBC News, 20 June 2002
http://news.bbc.co.uk/2/hi/science/nature/2128488.stm, BBC News, 15 July 2002
(4) Collision-Path Asteroid ‘Biggest Threat Yet’, PA News, 24 July, on Scotsman News
(5) See the government response to the recommendations of the Task Force on Near Earth Objects, available from the Near Earth Objects Information Centre
(6) Worden quote is from Military Perspectives on the Near-Earth Object (NEO) Threat, 10 July 2002. See the LINEAR Project website
(7) T Rex and the Crater of Doom, Walter Alvarez, Penguin 1998
(8) ‘Impacts on earth by asteroids and comets: assessing the hazard Chapman’, CR and D Morrison, Nature 367:33-39, 1994
(9) ‘LA Report – Reactions to 2002 NT7’, available from the Near Earth Objects Information Centre
(10) Preventing Armageddon, Tech Central Station, 22 July 2002
(11) National Security Needs Cut Into NASA’s Plutonium Inventory, Space News, 24 July 2002
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