The South Watch

Asteroid Ida. Rather larger, but probably looks much the same.

Yesterday an asteroid shot past the Earth at a distance of 5.4million km, about 14 times as far away as the Moon. Such events are pretty common, but what makes this 2012 LZ1 stand out is that the object involved is believed to be about 500m across. It was filmed by the Slooh Space Camera.

Five hundred metres is piddly compared to the “dinosaur-killer”. Had it hit the Earth we’re not talking the end of civilisation. But you wouldn’t want it to land on your head. There’s a bit of debate about how large the impact would be (it’s not like we can run full scale experiments), but this estimate, which seems to be at the lower end, has almost 200,000 square kilometres devastated if it hit land. If the collision is with the ocean the deepwater wave height of the tsunami is estimated at 22m 100km from splashdown, with widely varying estimates at 1000km away.

The size of the tsunami that would hit land depends on the shape of the Continental Shelf at a particular point, but the potential is there for a wave towering over the soon to be smashed skyscrapers of coastal cities.

Now it’s hardly time to panic. Five million kilometres is no small distance. 2012 LZ1’s next pass will be a lot further away, and probably so will the next few encounters that might earn the word close.

The clue to my interest lies in the name however. This asteroid was only discovered this year, indeed only four days before closest approach. Seems a bit late really. If the end of the world is to come I’d rather have a few weeks of debauchery if possible, and if we’re talking about a few lost cities, it might be nice to have enough warning to evacuate.

The discovery was made by the admirable Rob McNaught, discoverer of the finest comet to grace our skies in the last decade, almost 70 others and more than 400 asteroids.

McNaught is clearly an astronomer of great talent, and based on past interviews with him a really nice guy, but his achievements come in part because he pretty much has the southern skies to himself. While there are several programs looking for objects that could pose a threat to the Earth in the northern hemisphere, the same is not true in the south.

I have always considered it the responsibility of Australia, as the wealthiest and most scientifically advanced nation in the Southern Hemisphere, to step up to the plate on this one. It’s a responsibility we have resolutely shirked. Howard shut down the Australian program to scan for potential threats, with some choice comments from the then minister for science suggesting he had not the slightest grasp of the issues being dealt with here.

Last I heard, McNaught’s work depended on funding from NASA. (Hoping to get an update next week). This is true border security – something that could threaten the lives of millions, and it is operating on a budget that wouldn’t keep a single patrol boat in the water.

If providing warning of Apocalypse is not enough, McNaught is also involved in predicting the intensity of meteor showers/storms. He was one of the small number of people who correctly predicted the astonishing meteor storm of 2001, considered one of the highlights of their lives by pretty much everyone I know who saw it. Again, the budget for keeping McNaught working would be a lot less than what is spent on fireworks each New Year’s Eve. While the storm would have happened with or without his work, I for one only got to witness this event because I heard McNaught’s forecasts.

Update: I’ve interviewed McNaught for the Cool Scientist column. He was a bit bemused about the level of interest 2012LZ1 created, since it appears to be a particularly unlikely object to ever hit the Earth – it’s orbit currently never actually crosses that of the Earth, even though it gets very close at times. This may change as a result of gravitational tugs from other planets, but McNaught thinks he’s found other objects that justify far more interest.

On the other hand, the timing was very good for him. It turns out his funding was not from NASA (my mistake) but the University of Arizona, which runs one of the Spaceguard programs searching the skies for asteroids. Apparently they do this out of their own pockets as a mixture of public interest research and prestige building. Good for them. However, sadly last year they decided to concentrate the money they were investing in Spaceguard in their own telescopes, and withdrew funding from McNaught.

His costs are so small the ANU has been able to keep the project ticking over with temporary funding of their own, but that runs out this month. It may get renewed, but in the long run McNaught says the facilities he is using (the Uppsala telescope at Siding Spring Observatory) is in such poor condition that at some point soon repairs will be required if it is to keep going. At different times both Bob Brown and Rob Oakshot have taken a look and expressed support for the program, but it remains unclear if McNaught will get the measly resources needed to keep this project running.

About Stephen Luntz

I am a science journalist, specialising in Australian and New Zealand research across all fields of science. My book, Forensics, Fossils and Fruitbats: A Field Guide to Australian Scientists is out now through CSIRO Publishing. I am also a professional returning officer for non-government organisations. I'm very politically active, but generally try to restrict this blog to scientific matters.
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4 Responses to The South Watch

  1. Martin Bush says:

    I am certainly all in favour of better funding for astronomy, including asteroid surveys, but I have never really been persuaded by the ‘border defence’ line. I’d need some convincing that even a well-known asteroid’s impact on land could be predicted to better accuracy than “evacuate SE Australia”. An ocean basin tsunami warning for the far more likely case of a water impact is a bit better, but then if ‘border defence’ really is your motivation, arguably you’ld be better off spending the money on improving monitoring and warning systems for *actual* tsunamis rather than pinning down one source of potential tsunamis.

    • Warning systems for tsunamis are certainly a high priority, but I don’t see it as either/or. Even with the best warning systems in the world, people will not always have sufficient time to evacuate from really large events if the warning doesn’t come until the event occurs, so knowing that an asteroid was going to splash down in advance would be very useful, even if only a couple of days in advance. Both involve small costs compared to a lot of other things we spend money on, but the asteroid detection is particularly small, so I don’t see it as eating into monitoring costs.

      As to the precision of impact site if on land – not sure on that, I’ll ask McNaught what he thinks if I can get hold of him for interview.

  2. I asked McNaught about this, and he said that the accuracy of predictions of impact site would vary a lot. However, he claimed that under the best possible circumstances they could calculate a ground zero to an accuracy of one kilometre a couple of days in advance. He acknowledged that this would be rare, but he apparently believes that estimates precise enough to be useful would be quite common.

    Thinking about this a bit more it might be better no to imagine a strike on Melbourne, but something that could take out an area for a kilometre around that was known to be likely to hit in the vague area of, say, Ballarat. You might end up evacuating all the towns within a 100km radius, which would be a huge job but practical if Melbournians opened their homes. Only one town might be devastated, but you’d still be saving hundreds to tens of thousands of lives, depending on where it was.

    Of course, it is in McNaught’s interest, particularly given the update, to exaggerate the usefulness of his work, but given the truly staggering level of precision he managed for the 2001 Leonids I would not want to bet against him.

  3. Martin Bush says:

    Thanks for that Stephen. I’m not convinced yet, but I’ll adjust my credibility range based on your report. One thing that I wonderis what the variation of these things in the atmosphere is, in terms of fragmentation (and how that affects impact sites). Really big ones will certainly just plough through the atmosphere but I would imagine that’s not quite so definitie for smaller ones. Perhaps the difference is negligibly small though.

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