POTENTIALLY HAZARDOUS ASTEROIDS; FOUND - 3, LOST - 1.
In the past 18 months astronomers have discovered three asteroids that have very low, but measurable probabilities of hitting the Earth within the next 50 years. Sadly, due to the lack of an organised, global follow-up programme to track such objects, one has already been lost.
Although the likelihood of any of these three colliding is small, they are only a tiny part of the threat - over 85% of Earth crossing asteroids remain undetected.
Thanks mainly to the efforts of American search programmes, such as the joint NASA/USAF LINEAR (Lincoln Laboratory Near Earth Asteroid Survey) Project, the rate at which Potentially Hazardous Objects (PHOs) are being discovered is accelerating rapidly, but discovery is only the beginning. Further observations have to be made to determine the object's orbit before it can be declared safe (or otherwise), and there are simply not enough teams making these critical observations.
The scientific community is wrestling with the problem of how to explain the threat to the public without raising unwarranted fears. For example, were a real danger be discovered tomorrow, the UK would be left without guidance or organised expert advice. At the moment, the only country with any effective detection programme or any sort of organisation to advise the government is the United States. The rest of the world depends almost entirely on the US for their information.
In the House of Lords today , the Lord Tanlaw will question the government on what measures it is planning to take to set up a National Spaceguard Centre to monitor Earth crossing asteroids and comets. And to advise the government on the threat and what measures can be taken to protect ourselves from the most serious environmental threat known to science.
The subject of the impact hazard was first aired in the House of Commons when Mr Lembit Opik MP (LibDem) tabled an adjournment debate in March. John Battle, replying on behalf of the government, was very positive, acknowledging the seriousness of the threat and promising to investigate further action.
it is an acknowledged hazard to the UK and the world in general. At a major meeting of the world's experts in Turin last week, a resolution was passed urgently encouraging governments, especially those in Europe, to support the establishment of national Spaceguard Centres.
The UK is ideally placed to take a world lead in this international endeavour. We have an enormous reservoir of professional expertise, and a world lead in the design and development of instrumentation. Very soon the situation will arise when the probability of impact is high enough for concern, and the government will need a professional, expert team to advise it. It will be interesting to see how Lord Sainsbury responds to Lord Tanlaw's question.
THE good news is that astronomers have identified an asteroid that could be on a collision course with Earth. The bad news is that they have lost it.
The object, called 1998 OX4, was found last year by a team at the University of Arizona, who tracked it for two weeks.
The information the scientists gathered gave an approximate orbit for the object, which is believed to be several hundred yards in diameter and capable of continent-wide destruction if it were to collide with Earth.
A team at the University of Pisa, led by Dr Andrea Milani, used the orbital information to calculate the chances of a collision. He told a conference in Turin last week that there was a one-in-ten-million chance that it would hit the Earth in 2046 - slightly better odds than the 14 million to one on winning the National Lottery.
The asteroid is only the second such object found with a non-zero chance of a collision. And while a one in ten million chance is not enough to lose sleep over, it is embarrassing that 1998 OX4 has now been lost. The problem is that the orbit was not known with sufficient accuracy to track it. If it could be found, the chances are that more precise observations would dispel the fear of a collision.
Duncan Steel, a British astronomer who specialises in watching out for potential asteroid collisions, says that the dilemma posed by 1998 OX4 will become increasingly common. "The searches being done in the US are finding more and more objects that could potentially collide with Earth - so many that there aren't enough people to keep track of them," he says.
"The rate at which these objects are found has increased by three or four times in the past few years. False alarms are getting more frequent. Where we fall down is in following up on the original finds."
He is not too concerned about 1998 OX4. "But sooner or later we are going to find one with a one-in-a-thousand chance of colliding, and that could set off a panic," he says.
If it happened tomorrow, the Government would have to rely on experts overseas to give a proper assessment of the danger. "We need much better machinery in Britain to take responsibility for giving advice," he says.
Next week the Liberal peer Lord Tanlaw will ask a question in the House of Lords, seeking to discover whether the Government has any plans to establish a national "Spaceguard" programme of observation for near-Earth asteroids.
Dr Mark Baily of Armagh Observatory says that he believes such a programme is necessary and inevitable. "There are going to be more and more of these objects found. If we don't have a national agency, advice on the real level of risk will have to come >from astronomers who do this sort of work in their spare time, or >from those with no allegiance to the United Kingdom."
The lesson of 1998 OX4 is that, having found near-Earth objects, they should not be lost again, he says. "I won't lose any sleep over it," he says. "The risk it will hit us is much less than the risk of a totally unknown object doing so. All these calculations show is that we should go on tracking it - if we knew where it was."
Dr Steel does not rate highly the chances of finding 1998 OX4 again. "It's like finding a needle in a haystack, and then throwing it back in again," he says.
Many thousands of pieces of celestial rubble, big enough to devastate cities or to trigger a new ice age, may be in orbits that bring them close to Earth (Nick Nuttall writes). Many are elusive or invisible in the darkness of space. Astronomers have discovered 200 measuring at least 1km wide or more but suspect that the number may be as high as 2,000. There could also be about 5,000 comets that whip through our solar system.
The Earth's surface has some 150 large craters from past impacts. The biggest known happened 65 million years ago when an asteroid seven miles wide smashed into what is now the Yucatan Peninsula in Mexico, possibly triggering the extinction of dinosaurs. About 50,000 years ago a small asteroid, measuring about 30 yards across, hit Arizona, blasting a crater more than half a mile across. On June 30, 1908, a celestial object is believed to have hurtled into the Tunguska area of Siberia, flattening 1,250 square miles and knocking down millions of trees.
Astronomers search for 2020 vision .
Deep Impact and Armageddon gave Hollywood's version of what would happen if Earth was menaced by a stray asteroid. But the reality is far more frightening. Duncan Steel reports as the Lords prepare to raise the issue next week.
The bad news is that astronomers have identified two asteroids which could impact Earth within the next half century. The worse news is that one of those rocks has been lost in space.
This was not through incompetence. Think of it like cricket. An expert slip fielder cannot catch every nick off the edge. Especially if he's posted to square leg.
The Spaceguard search for such civilisation-threatening projectiles is being conducted with only part of the sky being scanned, often the wrong part. Sponsored by Nasa and the Pentagon, major efforts are under way in the US, but they cannot look during daylight hours, nor can they see the southern sky. Our front gate may be closed, but the rear door is ajar, and our windows wide open.
Asteroid 1998 OX4 was spotted last July by a university of Arizona team. Without collaborators able to take over the tracking, it was not followed long enough to secure definitive information about its future path. It is effectively lost, a needle grasped from the celestial haystack then tossed back. Maybe to prick our metaphorical backside rather painfully one day. Considering the spread of feasible orbits, researchers from the university of Pisa estimated there is a one in 10 million chance that it will slam into us in 2046.
Should we be worried? Only a few hundred yards in size, most likely 1998 OX4 will zip by again in 47 years. But if it hits then it will make an impression like a hundred hydrogen bombs.
The new data indicate this asteroid is particularly dangerous. In every loop about the sun it passes twice very close by Earth. This behaviour will continue for several centuries, unless it runs into us first. Present estimates of the likelihood of that occurring in 2039 are about one in 500,000.
Those are long odds, but this object is about a mile in size, big enough to kill a large fraction of humankind. We are talking about a million megaton explosion. There is something else to consider. Most asteroids seem not to be single lumps, but rubble piles, agglomerations of smaller boulders and town-sized blocks of rock and metal. 1999 AN10 is expected to pass very close by Earth several times, within a few tens of thousands of miles, much closer than the Moon. It is possible that our gravitational field will tear it apart, just like Jupiter tore comet Shoemaker- Levy 9 apart a decade ago, resulting in the string of impacts on that planet in mid-1994.
Maybe much of a broken-up asteroid like 1999 AN10 would miss a small target like Earth, but it's obvious that a million fragments each with a one-in-500,000 chance of blasting us is a dangerous proposition. Such things have surely happened before, many pairs of craters - and even chains containing six or eight impact scars - now having been identified around the globe.
What is clear is that because the US has charged ahead in its sky-scouring, turning up dozens of near-Earth objects every month, a can of worms has been opened. There are two vital requirements of any rational response.
First, other nations must co-operate in tracking these cosmic bullets, or we will lose more of the dangerous ones. Imagine if 1998 OX4 had been bigger, and with a 1% chance of hitting Earth say in 2010, but we'd let it slip through our grasp. That would be a recipe for alarm and trepidation, maybe mass suicides. Here, a little knowledge can certainly be a dangerous thing. We need to be sure. Second, it is in the national interest to have a domestic source of definitive information, to advise the government, media and appropriate authorities on a case-by-case basis. We cannot depend upon second-hand accounts from others.
Even if no other country does anything constructive, the US search projects will discover asteroids having uncomfortable miss distances at an accelerating rate. The relevant forward projections are intricate, but this is an area in which the UK has recognised expertise. A National Spaceguard Centre is essential if panics are to be avoided.
Realising this, the government responded favourably to a House of Commons debate in March, sparked by Lembit Opik, LibDem MP for Montgomeryshire, whose grandfather was an astronomer who pioneered research on the asteroid impact threat. Next Tuesday in the upper house Lord Tanlaw is scheduled to take the question further. A positive response will put the UK at the forefront of the global initiative to tackle this surprising menace.
We are entering a golden age of asteroid and comet research, with space missions to 13 such targets being conducted over the next dozen years. The dangerous ones, though, are those we have yet to discover. By the year 2020 we need 20/20 vision of our local cosmic environment, lest some lump of rock like that which killed the dinosaurs creep up on us unawares. We have been warned. Britain is ready to lead the way in Europe.
・ Duncan Steel is currently working at Armagh Observatory. His book Rogue Asteroids and Doomsday Comets (Wiley, Chichester and New York, 1995) was the first popular-level account of the impact hazard, leading to movies like Deep Impact and Armageddon.
Could Earth be hit by a giant asteroid in the next century?
The UK Government said on Tuesday that it had no immediate plans to set up a special centre to tackle the threat of asteroids hitting the Earth, despite warnings of an "extremely serious" risk.
Professor Bailey and Lord Tanlaw speaking on the BBC's Today programme The Science Minister said the government would look at setting up a National Spaceguard Agency following calls in the House of Lords for such a body, but not in the near future.
Lord Sainsbury told the House the government took the potential threat of a collision with an asteroid "very seriously", and that it was an issue where a "common international approach was essential"
But he said that it was not something for which there were any plans at present.
He was responding to a call from crossbencher Lord Tanlaw, who cited the case of a "potentially hazardous" rock, weighing two million tonnes and measuring one kilometre across, that may hit the Earth in 2044.
He told peers at question time that scientists predicted the asteroid, 1999 AN10, would miss the Earth by only 38,000 kilometres in 2027 but could "possibly impact" on a return visit.
Lord Tanlaw said a UK Spaceguard centre should be set up as part of a European Spaceguard programme to monitor so-called Near Earth Objects (NEOs).
He said 1999 AN10 posed a "risk for the next generation" which was a "low probability but a high-consequence risk". Lord Sainsbury said the possibilty of the asteroid hitting Earth was "extremely remote".
The estimated probability of an impact from the asteroid, discovered in January, was one in 500,000, he said.
The British government would prefer to cooperate with other nations to set up searchesfor near-Earth asteroids, rather than establish its own program, the British science minister told Parliament June 15.
Speaking in the House of Lords, science minister Lord Sainsbury of Turville told members that the preference of the government would be to work with fellow European Space Agency countries on any near-Earth object (NEO) detection programs.
"The Government take the potential threat of impact by near earth objects very seriously, but we regard it as an issue where a common international approach is essential," Sainsbury said.
Sainsbury was asked several times by members of the House of Lords if it would be prudent for Britain to establish its own "Spaceguard" program to search for NEOs, using such resources as the Armagh Observatory in Northern Ireland. On each occasion Sainsbury declined to show support for such a British-only effort.
"At the present moment, the Government have no plans to set up a national spaceguard agency," he said, although a final decision would wait until after the government reviewed reports from a recent NEO conference in Italy.
"Any additional work undertaken in the UK must have benefit over and above that being taken internationally."
The debate in the House of Lords comes three months after a similar debate in the other branch of Parliament, the House of Commons. At that time, John Battle, the Minister for Energy and Industry, told members the government would talk with British astronomers and other experts on ways the UK could support NEO research.
Since the March debate in the House of Commons, two asteroids have been discovered on trajectories which have small but non-zero probabilities of hitting the Earth next century.
Those discoveries have intensified interest worldwide in continuing and expanding the search for other NEOs.
Sainsbury said the British government does not consider the threat posed by NEOs to be a "trivial matter" but rather one that calls for cooperation.
"Of all subjects which come before this House, this is one in respect of which an international effort is the key," he said. "We shall play our part in that rather than acting independently."