An unnecessarily sensationalist article in the Guardian today, that covers the entire page 3 of the main section of the paper, reporting on the Near Earth Object Apophis – “It’s called Apophis. It’s 390m wide. And it could hit Earth in 31 years time” – Sensationalist because the article firstly relates out-of-date assessments of the risk of Apophis hitting Earth, from reports in 2004 [taking up half the article], before quoting Alan Fitzsimmons, an astronomer from Queen’s University Belfast on the current assessment.. extracts over the fold, or you can compare this press release on 28th November from the Particle Physics and Astronomy Research Council [PPARC].Here are the opening paragraphs setting the tone –
In Egyptian myth, Apophis was the ancient spirit of evil and destruction, a demon that was determined to plunge the world into eternal darkness.
A fitting name, astronomers reasoned, for a menace now hurtling towards Earth from outerspace. Scientists are monitoring the progress of a 390-metre wide asteroid discovered last year that is potentially on a collision course with the planet, and are imploring governments to decide on a strategy for dealing with it.
Nasa has estimated that an impact from Apophis, which has an outside chance of hitting the Earth in 2036, would release more than 100,000 times the energy released in the nuclear blast over Hiroshima. Thousands of square kilometres would be directly affected by the blast but the whole of the Earth would see the effects of the dust released into the atmosphere.
Worried yet? Read on..
Apophis had been intermittently tracked since its discovery in June last year but, in December, it started causing serious concern. Projecting the orbit of the asteroid into the future, astronomers had calculated that the odds of it hitting the Earth in 2029 were alarming. As more observations came in, the odds got higher.
Having more than 20 years warning of potential impact might seem plenty of time. But, at last week’s meeting, Andrea Carusi, president of the Spaceguard Foundation, said that the time for governments to make decisions on what to do was now, to give scientists time to prepare mitigation missions. At the peak of concern, Apophis asteroid was placed at four out of 10 on the Torino scale – a measure of the threat posed by an NEO where 10 is a certain collision which could cause a global catastrophe. This was the highest of any asteroid in recorded history and it had a 1 in 37 chance of hitting the Earth. The threat of a collision in 2029 was eventually ruled out at the end of last year.[emphasis added]
Now that’s not to say that there isn’t still a risk.. nor that the concern expressed in the article isn’t real or valid.. but the way the report is presented invites scorn.
Here’s Alan Fitzsimmons on the current assessment, in the Guardian –
Alan Fitzsimmons, an astronomer from Queen’s University Belfast, said: “When it does pass close to us on April 13 2029, the Earth will deflect it and change its orbit. There’s a small possibility that if it passes through a particular point in space, the so-called keyhole, … the Earth’s gravity will change things so that when it comes back around again in 2036, it will collide with us.” The chance of Apophis passing through the keyhole, a 600-metre patch of space, is 1 in 5,500 based on current information.[emphasis added again]
So, after all that, the chances of Apophis passing through that particular region in space is 1 in 5,500.. and, I’d suggest, the odds of the orbit being changed in such a way as to result in a subsequent collision with Earth are either larger still or unknown.
The only really interesting aspect of the article is in the description of the methods under consideration for deflecting such Near Earth Objects should that be required.. unfortunately, due to everything else in the article we get the truncated version –
The Advanced Concepts Team at the European Space Agency have led the effort in designing a range of satellites and rockets to nudge asteroids on a collision course for Earth into a different orbit.
No technology has been left unconsidered, even potentially dangerous ideas such as nuclear powered spacecraft. “The advantage of nuclear propulsion is a lot of power,” said Prof Fitzsimmons. “The negative thing is that … we haven’t done it yet. Whereas with solar electric propulsion, there are several spacecraft now that do use this technology so we’re fairly confident it would work.”
The favoured method is also potentially the easiest – throwing a spacecraft at an asteroid to change its direction. Esa plans to test this idea with its Don Quixote mission, where two satellites will be sent to an asteroid. One of them, Hidalgo, will collide with the asteroid at high speed while the other, Sancho, will measure the change in the object’s orbit. Decisions on the actual design of these probes will be made in the coming months, with launch expected some time in the next decade. One idea that seems to have no support from astronomers is the use of explosives.
Meanwhile, back on planet Earth *ahem*
In spring next year, there will be another opportunity for radar observations of Apophis that will help astronomers work out possible future orbits of the asteroid more accurately.
If, at that stage, they cannot rule out an impact with Earth in 2036, the next chance to make better observations will not be until 2013. Nasa has argued that a final decision on what to do about Apophis will have to be made at that stage.
For comparison here’s a much less sensationalist press release on NEOs using many of the same sources, which includes this paragraph –
Studies of one such asteroid (Apophis), which was discovered in June 2004, have shown that there is a low probability that this object will impact the Earth in 2036. This has raised a whole series of issues about the prospect of deflecting the asteroid before a very close approach in 2029. Government’s across the world are looking at the issue and in particular at the technologies and methods required to carry out an asteroid deflection manoeuvre in space.[added emphasis]