Blogging from the Highlands of Scotland
'From fanaticism to barbarism is only one step' - Diderot

Saturday 25 December 2004

Avoid Earth - 29th April 2029

I had not planned to write here until the middle of next week, but I think this warrants a mention. I keep an eye on NASA's Near Earth Object Program (click on 'Impact Risk' from there) and for quite a while now there has been one object which was flagged up as having a fairly remote possibility of impacting the Earth, but quite a way into the future (reference 1997 XR2, 0.230 km diameter, year 2101 - 1 on the Torino scale, the lowest classification). More recently a second object has been flagged up has having a similarly remote likelihood of hitting the Earth, somewhat sooner, but still comfortably far in the future for someone like me who will probably be dead long before this might happen (reference 2004 VD17, 0.580 km diameter, year 2091 - again 1 on the Torino scale), although it is twice as large as 1997 XR2.

Just a few weeks ago I noticed a third object had similarly been flagged up, initially with a classification of 1 on the Torino scale, but I noticed some days ago that this had been raised to '2'. This evening, its classification has again been raised, this time to 4 on the Torino scale. This object is called 2004 MN4 and has a diameter of 0.390 km and the highest current likelihood of it colliding with Earth appears to be on 13th April 2029; the likelihood is currently put at 2.2e-02, which converts to a 1 in 45 chance it may strike - another way of looking at it is that there is 97.80000000% chance the asteroid will miss the Earth. I shall be watching for updates on the Near Earth Object Program website in coming days and weeks to see whether further observation of this object's trajectory seem to be increasing or decreasing the likelihood of a strike. What is striking, to employ a bad pun, is that this object appears to have an orbit very similar to that of Earth, and that even today it seems to be quite close to us (see * - at end of message), although one presumes this does not currently pose a risk - to see its orbit in relation to Earth, click on 'Orbit diagram and elements available here' link from the 2004 MN4 page; you can vary the time frame to any date you wish.

The UK's National Space Centre website has this report about object 2004 MN4:

Asteroid 2004 MN4 Torino - rating increased

"The asteroid, designated 2004 MN4, has had its Torino Impact Hazard Rating raised from two to four. Such a rating applies to a close encounter, with 1% or greater chance of a collision capable of causing regional devastation.

Dr Alan Fitzsimmons of Queen’s University Belfast advised the NEO Information Centre that the object would remain observable until summer 2005 and will be observable on many more occasions before the potential impact date. This will allow scientists a good window of opportunity to continue observations and refine their understanding of the asteroid’s orbit.

The Italy based NEODyS, who monitor the risk from newly discovered asteroids and comets, say, "Most likely, that is in 59 cases out of 60, the impact probability will go to zero after enough new observations have been obtained and processed."

* - in fact over the past week and for the next few days this object appears to be very close to Earth and I imagine (and hope!!) that the only reason it has not been flagged up as an urgent threat is that because it is actually occurring now, its orbit is under the closest possible scrutiny and its present orbit has been tracked with great precision. Of course, 20 or 30 years into the future the calculations are probably not yet quite so accurate. Now, unless something equally 'dramatic' comes to my attention, I will be silent until the middle of the coming week - rest assured.

UPDATE: (Monday 27DEC04 11.30 GMT) The 2004 MN4 page is now showimg the impact risk at the increased level of 1 in 37 (up from 1 in 45).

2nd UPDATE (Tuesday 28DEC04 11.10 GMT) The 2004 MN4 page now shows much better news; the 'danger' pass in April 2029 has been completely eliminated and there remain (at time of writing) only two passes where there is a Torino scale reading of '1'. Panic over ...

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