Unrecognised risk: Earth may lie in the path of many thousands of unseen 'dark' comets.
Credit: NASA
Rob McNaught an astronomer from Australia's Siding Spring observatory in Coonabarabran, New South Wales, who has had several comets named after him, agreed that dark, inactive comets would be under-represented in the Near Earth Object surveys.
But Paul Francis, from the Australian National University in Canberra, said the researcher's theory was "speculative", in particular because impact craters were hard to date accurately.
"The best guess from the rate at which these comets come in is that they are not a risk," said Francis. He said a comet impact of a similar scale to the one that wiped out over 2,000 square kilometres of forest at Tunguska in Siberia was a "one-in-10-million-year event", while a continent destroying impact was a one-in-60-million-year event.
"That's not to say it may not happen for 20 million years and may happen tomorrow, but it's not very likely."
Earth under threat from dark comets
Sure, I have no doubt. A comet will inevitably hit the earth wreaking devastation and species extinction. I also think that we ought to as a species get together for a change and set up a system in orbit that can send such objects into a safer deflection so that we have a kind of permanent insurance policy. Perhaps on the moon or in a partcularly useful near earth orbit. Laser systems that can be aimed at such objects as they enter into the inner solar system so that oblation of the surface acts as a method of slowing down or speeding up the comet from a distance. Slow but steady in other words. What is needed is very accurate imaging and locating of such objects, careful and dedicated analysis of such objects for proper targeting. Seems that the US, Canada, China, Russia, Japan and the EU would be well off considering a shared proposal and shared costs in this. Of course, judging from the news today, the Brits and the French who are ostensibly allied do not even bother to inform each other about submarines in the Atlantic carrying nukes. Getting together for a comet seems rather far fetched but logical nonetheless.
How can it be a comet without a tail?
"Dark" comets don't heat up as they approach the inner solar system, start spewing ice and gas behind them? Then it's not a comet, is it now? It's an asteroid.
Why
I'd like to know _why_ "dark" commets are harder to spot than asteroids. I don't understand why a layer of dust which would probably be similar in composition to that of an asteroid would be harder to spot than an asteroid.
Secondly, dark surfaces absorb more heat. As the "dark" commet moves into the inner solar system, greater heating would no doubt cause high levels of outgassing. And the resultant tail would no doubt be visible against the background of space.
Perhaps the writer meant that exhausted commet cores would be harder to spot (no more outgassing) than regular commets. I would agree with that assertion, but I doubt the assertion that such a commet would be harder to spot than, say, a carbonaceous chondrite asteroid. Think "Mathilde."
Great...
Well that's just perfect, now we have to face planet killing ninja comets, we're doomed.
Earth under threat from dark comets.
Christ sake!!! purveyors of doom and gloom. Do you people sit there all day just to think up any or all pessimistic reasons to the destruction of the planet?? In the sixties all these morons walked around the cities touting "the end is near" - and we are all still here.
Sure we live on a little ball with significant perils in space (and elsewhere) that could wipe us out at any moment, but surely we can organise the "STAR WARS" technology to track the heavens to perhaps deal with such a catastrophic "hit" instead of trying to blow the shit out of each other on earth. Perhaps we deserve to be "hit".
Get a life - how about some optimistic views. I happen to think the human race in general will rise to these challenges as they happen, They always seemed to have done!!!
Re: Earth under threat from dark comets.
Rise to these challenges as they happen? What?, like the bang-up job we are doing with Global Warming? Perhaps you need to re think your opening phrase as well, not really fitting in well with a Science site.
re: Earth under threat from dark comets...
"In the beginning GOD made the heavens and the earth..." Perhaps as we try to understand our observations, we should consider the Creator has a pretty good plan, that has worked out fairly well, in spite of us!
Earth under threat from dark comets
United Nations may take up the issue of earth's vulnerability before all member countries to pool up funds to protect mother earth from such hazards.
Comets? How about the solar max?
With the increased gravitational and EM forces affecting the Sun when passing through the plane, coupled with the Suns recent inactivity and a buildup of plasma. I'm more concerned about coronal ejections with an extremely active cycle when we begin to really intersect with the plane. That regular solar cycles are a result of our changing position with the core of our galaxy. It's too quiet IOW's
The fact that we may see objects change orbits and pose a threat is secondary at this point. We will lose our satellites and quite possibly see complete disabling of our semi conductor technology... power grids automobiles cells anything that has chips.
A nice comet would just be icing on the cake.
CMEs vs comets interactions...
Any thoughts concerning the coming alignment of the sun, earth and the black hole at the center of Milky Way in 2012?