Earth Under Threat From Dark Comets

An anonymous reader writes "Comets could be the most significant impact hazard to Earth, with sky surveys underestimating the number that are potentially devastating by a factor of between 10 and 100, UK astrophysicists say."

Comments

Slashdotted

[Spazztastic]

Already down. There goes my chance of calling FUD.

Re:Slashdotted

[morgan_greywolf]

Here we go, try this article from New Scientist, which has the same story.

Hazardous comets and asteroids are monitored by various space agencies under an umbrella effort known as Spaceguard. The vast majority of objects found so far are rocky asteroids. Yet UK-based astronomers Bill Napier at Cardiff University and David Asher at Armagh Observatory in Northern Ireland claim that many comets could be going undetected. "There is a case to be made that dark, dormant comets are a significant but largely unseen hazard," says Napier.

The article goes on to say that "dark comets are not unheard of. They occur when an 'active' comet's reflective water ice has evaporated away, leaving behind an organic crust that only reflects a small fraction of light."

Re:Slashdotted

[clang_jangle]

Try this one instead.

Re:Slashdotted

[needs2bfree]

Organic != made by life. Means nonmetals, so Carbon, Nitrogen Sulfur and related compounds.
Disclaimer: IANAC (I Am Not A Chemist)

Re:Slashdotted

[dkf]

Organic != made by life. Means nonmetals, so Carbon, Nitrogen Sulfur and related compounds.

It specifically means Carbon. There's really quite a bit of it about in space, and the process of evaporating off all the ice from the comet will mean that that which is there has been thoroughly concentrated to make something rather like soot. Such materials, especially in ultra-low gravity environments (so preventing the collapse of complicated micro-strucutres), are incredibly black, making the comet harder to see than a black cat in a coal cellar. At night with no torch.

The New Scientist article goes on to mention that the best hope of spotting these things may be in the infra-red range, as they'll be absorbing all the sunlight that falls on them and reradiating it. Sounds tricky to me, but just might work...

Re:Slashdotted

[linnorm]

Such materials, especially in ultra-low gravity environments (so preventing the collapse of complicated micro-strucutres), are incredibly black, making the comet harder to see than a black cat in a coal cellar. At night with no torch.

How much more black could they be?

Re:Slashdotted

[Vorpix]

none more black.

Another reason for fear

[IamGarageGuy 2]

C'mon, there are hundreds of ways for me to die everyday. If I have to start worrying about the sky falling on me, I might as well pack it in now.

Re:Another reason for fear

[norppalaho]

...If I have to start worrying about the sky falling on me...

Vitalstatistix, Is that you?

Re:Another reason for fear

[Chabil Ha']

My wife is a worry-wart and I use this argument against my spouse for doing things: I could walk outside and have my head replaced by a falling meteor. Does that mean that I shouldn't go out today? The chances for that are enormous to the point of why should I even worry about it? I can't let the possibility of bad things happening overshadow the probability. Probability is what we should be using in risk modeling, not possibility, because hey, anything is possible .

I mean hey, with the crash of that airplane near Buffalo, NY, do think the occupants of that house thought to themselves, "I think I should sleep in a hotel tonight because a plane might crash on my house?" No, because if you were to enumerate all the possible ways you could die, you might as well just kill yourself and be done with it.

But here's the real question: even if we did know when something was coming, is there really anything we could do about?

Re:Another reason for fear

[Teun]

According to all Hollywood studies it would be safest to leave the USofA...

Seriously? WTF?

[zappepcs]

"Comets could be the most significant impact hazard to Earth

Just what are the "other" impact hazards? I'm very curious about this.

Re:Seriously? WTF?

[meringuoid]

Just what are the "other" impact hazards? I'm very curious about this.

Asteroids.

Asteroids orbit nearer the Sun, and many of them have paths that cross Earth's orbit quite frequently. They're a menace all right, but a menace that can be mapped and measured. Comets on the other hand have long, highly elliptical orbits that carry them far from the Sun. Though any given comet won't pass near the Earth anywhere near so often, they exist in colossal numbers, and for all we know one could come barrelling out of the dark to kill us all next month. We could in principle track every rock of dangerous size in the inner solar system. We haven't a prayer of tracking all the comets.

Re:Seriously? WTF?

[XxtraLarGe]

Though any given comet won't pass near the Earth anywhere near so often, they exist in colossal numbers, and for all we know one could come barrelling out of the dark to kill us all next month.

Sounds like there's not really any reason to worry about it then if there's nothing we can do. Isn't that the definition of FUD?

Re:Seriously? WTF?

[mrsquid0]

>>"Comets could be the most significant impact hazard to Earth
>Just what are the "other" impact hazards? I'm very curious about
>this.

Asteroids are the other impact threat. There is also a small risk from man-made space junk. The biggest threat is comets because they tend to be moving far faster than asteroids typically do (near parabolic orbits vs low-eccentricity elliptical orbits), so the kinetic energy in a comet impact can be much higher than in an asteroid impact. Another problem with comets is that they can come at us from the direction of the Sun, so it can be very hard to detect them before the impact shockwave turns us to jelly.

Re:Seriously? WTF?

[Anonymous Coward]

sperm wales and pertunias...

Re:Seriously? WTF?

[osu-neko]

Sounds like there's not really any reason to worry about it then if there's nothing we can do.

If the utterly false statement that "there's nothing we can do" were true, you'd have a point there.

Isn't that the definition of FUD?

No. In fact, it's almost entirely unrelated to FUD in the usual sense. FUD usually involves getting you to choose one option over another due to spurious reasons, e.g. choose product A because product B is open-source so the bad guys can insert exploits into the code (they accept contributions from anyone, after all -- this was an argument my old boss made). Trying to move people from a situation where they're unprepared to deal with a real threat to a situation where they're better prepared for it is pretty much the opposite.

I Call FUD Anyway

[mfh]

It's down for a sinister reason! They don't want us to READ the articles and become informed of the truth!!!

Also, why the racism? Just because the comets are DARK doesn't mean they are evil. RACISTS!

DCC Trading

[Anonymous Coward]

My greatest fear is that people will view this as something that they have no control over, thus inducing a sense of complacency. Complacency kills!

But there is hope. I propose a Dark Comet Credit (DCC) trading system, whereby planets that are in danger of being struck by dark comets purchase dark comet credits from planets that aren't in danger.

It may not be a perfect plan, but it's better than doing nothing.

don't be so judgmental

[jollyreaper]

Just because these comets hang out in the furthest, coldest reaches of the solar system, don't reflect light all that well and listen to cradle of filth, that doesn't make them all dark! Goth, maybe, but not dark. You just don't understand them.

Re:Launch Nukes

[navyjeff]

Looks like you missed the reference.

Threat From Dark Comets???

[Nomaxxx]

Hurry up! Find Bruce Willis!!!

No torch?

[PeeAitchPee]

are incredibly black, making the comet harder to see than a black cat in a coal cellar. At night with no torch.

Who uses torches in their "coal cellar"? What are you looking for, Frankenstein? ;-)

Re:No torch?

[Ray]

Way too subtle. Remember, speakers of "the Queen's English" require giant, cartoon stomping feet to indicate humorous content is about to follow.

Re:No torch?

[morgan_greywolf]

Monty Python? Benny Hill? Blackadder? Douglas Adams? Rowan Atkinson?

Subtle innuendo has long been a staple of British humour.

Re:No torch?

[aliquis]

... and that comes from a guy who lives (?) in the country where they must add laughter to the TV series so you know there may have been something funny even if you didn't got it.

Re:No torch?

[ChatHuant]

Monty Python? Benny Hill? Blackadder? Douglas Adams? Rowan Atkinson?

Subtle innuendo has long been a staple of British humour

Benny Hill? Subtle innuendo? What are you, French?

Oblig....

[SIR_Taco]

Shouldn't we put brown paper bags over our head or something?
If you like.
Will it help?
No.

Re:Don't worry

[Anonymous Coward]

any comet will be taken out by an asteroid, satellite or stray sub way before it gets near a population centre

Fair enough, but:

1) How are we going to get those Subway restaurants to stray?

2) What will happen to all those $5 foot longs after the impact?!?

Of all the ways to go

[hwyhobo]

Of all the ways to go, at least here is one where you don't have to say, "Well, that was a bonehead thing to do..."

Re:Silly article

[nyctopterus]

Actually, impacts the size of the Yucatan K/T event are global in scope, and do not occur on average every 60 million years. Even if every major extinction event was caused by a an impact (which is highly doubtful), they are much more widely spaced than a sixty million year average.

Maybe what we're looking at is something more like the Younger Dryas impact event hit every 60 million year on average. Which, though unlikely, would of course be a major fricken disaster for humanity if it happened within our lifetimes.

Extrasolar objects

[symbolset]

Somebody else covered asteroids, so I'll touch on another risk: extrasolar objects. You see, a lot of discussion is made of object in our solar system because they are things we have to study for long periods of time; we can see them. However our solar system is orbiting the center of our galaxy in concert with a vast quantity of other material. Things can and do achieve escape velocity from our solar sytem, like the Voyager probes.

Not all the mass in our galaxy belongs to a star. Some of it - the remnants of supernovae, agglomerations of interstellar dust, stray comets ripped away but not captured by close passing stars - wanders the dark realm between the stars. This stuff is hard frozen and the vast majority of it is fine dust. Unfortunately not all of it is. The Earth is struck by extrasolar meteors every day, and some of them have good size. Because of their different origin they can be moving much faster relative to the Earth than an object that's been circling our common star for billions of years.

It would be unfortunate if we were struck by one of these objects that is a mile or more in diameter.

Re:Impacts are good

[Dragonslicer]

If it weren't for this massive impact some 65k years ago we would still be voting for lizards

I know we Americans don't pay much attention to the SI system, but you might want to check your prefixes.