Meteorites are normally associated with mass extinctions, but could some be good for the Earth’s health?
From killing off the dinosaurs to starring in multiple Hollywood blockbusters, meteorites have long fascinated millions.
Dr Ted Nield, Editor of Geoscientist magazine, talks to Beki Hill about his latest book, Incoming!; the chances of Earth being hit by a meteorite, and the all important question of whether the best option would be to send up the crew of Armageddon. And have all meteorites have been bad for the planet?
Listen to find out…
Podcast: Play in new window | Download (Duration: 6:33 — 9.0MB)
For a full review of this book, you can read Djuke Veldhuis’ article in the Reviews section.
Transcript:
Beki Hill: Imagine a meteorite is headed straight for Earth. You know that Chicxulub wiped out the dinosaurs; you don’t want another mass extinction… what do you do? Well, it may calm your nerves to know that there are people thinking about that very possibility as we speak. I’m Beki Hill, and I went to get some expert advice from Dr Ted Nield about the great chunks of rock hurtling around in space. But while I was asking whether we should be battening down the hatches, he also gave me an insight into his latest book and explained that not all meteorites are as bad as we might think.
Ted Nield: My name is Ted Nield, I am the editor of the magazine Geoscientist, and I do that three days a week and the rest of the time I write books.
BH: Your new book, incoming, is about meteorites and whether or not we should be worried…
TN: Well, the theme I wanted to explore in the book is: what is the meaning of an event? What then unfolds a result of that event depends more on context than it does on the event. The end of the Cretaceous was a terrible time to be alive – it was a hothouse, acid rain spattered world, with anoxic oceans, and then the last straw, the straw that broke T-Rex’s back, perhaps, was the arrival of a meteorite which cant have done anything but harm.
But the really new scientific story in the book is about this newly discovered fact that the Earth was bombarded by meteorites for about 10 million years, a long time ago in the Middle Ordovician, about 470 million years ago. And meteorites at that time were so common we’ve even started to find fossil meteorites. And one of these turned up in Sweden in the 1950s…
BH: And how big was it?
TN: About 10cm across. They have found several 100 sizeable meteorites in rocks of that age. And yet, that time, in Earth history also saw the big burgeoning in biodiversity that there has ever been. The knowledge that the Earth was being pelted in that way for long presents an explanation – and that is that if you disturb an environment physically you sterilise the endemic population, which allows new species to move in and that increases biodiversity, so you get new species created. Now the Mid Ordovician was an equable time for live, as opposed to a ghastly time for life, like the end of Cretaceous, and so under those circumstances it stimulated life rather than trying to exterminate….
BH: So that was a good meteorite?
TN: That was a good meteorite. Of course, no such thing as good meteorites and bad meteorites, it’s just the circumstances are different.
BH: So have there been a lot of meteorites that have hit the Earth?
TN: Well I mean meteorite flux to the Earth is a fairly constant figure; its somewhere between 30 and 40 thousand tons a day, which sounds like a lot but of course in comparison to the mass of earth its so trivial it actually doesn’t make any difference.
BH: So, how likely is it that we’re going to get struck by another meteorite on a sort of dinosaur scale?
TN: Since we learnt about way the dinosaurs went there has been an international effort to map Earth-crossing asteroids, which are the dangerous ones, because most asteroids are perfectly safe – they’re out there between Mars and Jupiter. But occasionally they get catapulted by gravitational effects or collisions into earth crossing orbits and they reckon that they’ve mapped about 75% of the total population of these things, and not one of the big asteroids shows any sign of hitting the Earth in the near future. What the effect of this has been to reduce the global risk of death by meteorite – every human being on the face of the Earth faces a chance of one in 720000 of dying by meteorite.
BH: Has anyone ever died of a meteorite?
No, there are no reliable historical records of anybody ever being killed by a meteorite. People have been struck by them, but never died directly of them as far as we know. Those accounts that we do have of humans and indeed even animals being struck and killed by meteorites are dodgy in one way or another. Either they’re legendary or they’re known to be fraudulent.
BH: If a meteorite, a big enough one that could cause serious damage, one that we had to worry about, came along and we thought might actually collide with the earth, is there anything that we could do about it?
TN: Yes, and it wouldn’t include sending up Bruce Willis and a bomb. I mean that Hollywood solution is always a bomb because that’s for dramatic necessity; you need a bang at the end of a big film. But it would be a very stupid thing to do, because of course it would turn one large impacter into several smaller impacters, and you would not really know where they were going. If you see the thing in advance, with enough notice, the clever thing to do would be to nudge it out of its orbit. Now you wouldn’t do that by cosmic snooker – you wouldn’t try and hit it with something. You’d try and divert it by doing something clever like putting an ion engine on it, which would deliver a constant small force in one direction which over many many years would slightly change the orbit. So instead of hitting the earth it would slowly graze by. You could also try altering the colour of the surface because a lot of asteroids behave the way they do because they’re differentially heated – they’re dark on one side, light on the other and that has a long term effect on the way that they orbit. It is a problem that does have a potential for an answer.
BH: Does that mean there’s people who actively research into what to do if a meteorite or asteroid comes near?
TN: There’s a lot of people who speculate as to what could be done, there are even conferences about it, and the Project Spaceguard, which is still a global effort. But I’m a practical fellow and I think that people, if they’re going to worry about things, they ought to worry about something they can do something about. And they don’t need to look as far as outer space – all we have to do is look at each other. We’re the biggest threat. Yes these things are important, we need to keep watching the skies, but basically there’s much more important things, much closer to home that we can do something about now.
BH: Meteorites are not our biggest problem…
TN: Meteorites are not our biggest problem, and indeed in many ways they have been our friends throughout history. They may have stimulated life to become complex in first place. They did away with dinosaurs and that was surely good news for us, wasn’t it so we cant complain.
Image: Under Wikimedia Commons, courtesy of NASA
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