Giant comets may threaten Earth: astronomers (Update)

December 22, 2015

A comet strike is believed to have ended the reign of the dinosaurs 65 million years ago
A comet strike is believed to have ended the reign of the dinosaurs 65 million years ago
Planet Earth could be at higher risk of a space rock impact than widely thought, according to astronomers who suggested Tuesday keeping a closer eye on distant giant comets.

Most studies of potential Earth-smashers focus on objects in the asteroid belt roughly between Mars, Earth's outside neighbour, and Jupiter on its other flank, said the researchers.

But they noted that the discovery in the last two decades of hundreds of giant comets dubbed centaurs, albeit with much larger orbits, requires expanding the list of potential hazards.

These balls of ice and dust, typically 50-100 kilometres (31-62 miles) wide, have unstable, elliptical orbits that start way beyond Neptune, the most distant planet from the Sun.

Their paths cross those of the giant planets Jupiter, Saturn, Uranus and Neptune, whose gravity fields occasionally deflect a comet towards Earth—once about every 40,000-100,000 years.

As they draw closer to the Sun, the comets would gradually break up, which is what causes the trademark cometary debris tail—"making impacts on our planet inevitable".

"The disintegration of such giant comets would produce intermittent but prolonged periods of bombardment lasting up to 100,000 years," the research team wrote in the Royal Astronomical Society journal, Astronomy and Geophysics.

And they argued that "assessment of the extraterrestrial impact risk based solely on near-Earth asteroid counts, underestimates its nature and magnitude."

They noted that a single centaur contains more mass than the entire population of Earth-crossing asteroids discovered to date.

"In the last three decades, we have invested a lot of effort in tracking and analysing the risk of a collision between the Earth and an asteroid," said co-author Bill Napier of the University of Buckingham.

"Our work suggests we need to look beyond our immediate neighbourhood too, and look out beyond the orbit of Jupiter to find centaurs.

"If we are right, then these distant comets could be a serious hazard, and it's time to understand them better."

Scientists believe a comet bombardment may have kickstarted life on Earth by bringing water and organic molecules.

A comet strike is also a leading contender for having ended the reign of the dinosaurs 65 million years ago.

The team said no risk was "known to be imminent", although cometary encounters were largely unpredictable.

"A centaur arrival carries the risk of injecting, into the atmosphere... a mass of dust and smoke comparable to that assumed in nuclear winter studies," wrote the researchers, referring to the hypothesised climate effects from the soot that would be released by firestorms caused in an atomic war.

"Thus, in terms of magnitude, its ranking among natural existential risks appears to be high," they said.

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22 comments

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Gigel
4 / 5 (4) Dec 22, 2015
Studies of potential impactors rather concentrate on those bodies lying in the immediate vicinity of Earth: large bodies farther away and smaller, 10-100 meter bodies lying just 1-2 days away from an impact with Earth. Such bodies often surprise astronomers as they are discovered just as they enter the atmosphere, e.g. the Chelyabinsk meteor that blew up in the air in 2013. A few have been reported since 2000, just to give a hint on the chance of encounter.

A 30-100 meter meteor coming on a trajectory closer to the vertical can survive atmospheric entry up to impact and cause major problems: tsunamis and destruction on shores or dust clouds and solar dimming, crop failure and famine.

This kind of threat requires urgent building of automated telescopes around the world and preferably into space too (where the Sun can be covered so as to see close to its position). Such systems are not very complex or expensive. Telescopes under 1 meter in diameter can perform the search.
jjgeibel
2.5 / 5 (6) Dec 22, 2015
I think that the Younger-Dryas cooling event and extinction was caused by one of these large comets that came into our atmosphere at an angel breaking up as it enter our atmosphere much like the Shoemaker-Levy comet that hit Jupiter. Because it was mostly ice with some dust, there were no impact creators only a small amount of dust that can be found from Europe through the US. Who knows how far into the Pacific the comets material was deposited? In any case, the first effects would have been shock waves, heat and fires across most of North America, but within a short period of time the atmosphere would cool to the point that all of the dust and water vapor in the atmosphere would begin falling as torrential rains that may have lasted for months. This would explain the largest expansion of Nevada's great basin lakes near the beginning of the Younger-Dryas. The smaller of these lakes were already dried up by the end of the Younger-Dryas cooling 11,000 years ago.
howhot2
3.9 / 5 (7) Dec 23, 2015
You know what? I think I would worry about these comets after we solve the problem of global warming.. With global warming you know it's certain in the next century.
jsdarkdestruction
4.8 / 5 (5) Dec 23, 2015
Scary to think of what it would be like to have one hit.
I thought an asteroid 10 km(6miles) in diameter caused the dinosaur extinction. I looked on Google and found a few articles from 2013 saying it was likely a comet by the studies authors but controversial and Not decisive. Has new information supporting a comet been found?
Gigel
3.9 / 5 (7) Dec 23, 2015
A 10 km comet can destroy a good part of Earth's ecosystems, i.e. cause the disappearance of dinosaurs. A 100 km diameter one would cause destruction that probably has not happened since the formation of Earth. It may obliterate life or at least return it to the stage of bacteria. The winter it would cause could keep for years or decades. It could ignite volcanoes where there haven't been before. The initial crater would reach to the astenosphere. Something like that hasn't been recorded since fossils appeared.
Gigel
3.4 / 5 (5) Dec 23, 2015
I thought an asteroid 10 km(6miles) in diameter caused the dinosaur extinction. I looked on Google and found a few articles from 2013 saying it was likely a comet by the studies authors but controversial and Not decisive. Has new information supporting a comet been found?

Well, comets are typically 10 km in diameter. What this article speaks of is something much larger that normally doesn't roam into the inner solar system (if it did it would probably be known as a small planet).
my2cts
3.8 / 5 (13) Dec 23, 2015
You know what? I think I would worry about these comets after we solve the problem of global warming.. With global warming you know it's certain in the next century.


We did solve it. We have to uphold the truth that life is most important in life in all things. That's all it takes and that is the only way. There is no other.


Off course. Now take your pills.
Rocco sporgenti
2 / 5 (4) Dec 24, 2015
I would venture to guess that these periodic impacts (of comets or remnants, or just raining down from passing comets) have brought the diversity of life we see on Earth today. Every mass extinction has been has been followed by a rise of different dominant life forms. Even as a geologist, I find it hard to believe that all the life on Earth arose from the same evolutionary pathway.
my2cts
3.4 / 5 (10) Dec 25, 2015
no better than Hitler.

You are on a roll, witch finder general.
When will you start burning people at the stake ?
antialias_physorg
4.3 / 5 (9) Dec 25, 2015
He's no better than Hitler.

You've just been Godwin'd. You lose.

https://en.wikipe...in's_Law

Godwin's law (or Godwin's rule of Nazi analogies)[1][2] is an Internet adage asserting that "As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1"...

... there is a tradition in many newsgroups and other Internet discussion forums that once such a comparison is made, the thread is finished and whoever mentioned the Nazis has automatically lost whatever debate was in progress.[8] This principle is itself frequently referred to as Godwin's law.
my2cts
3.2 / 5 (9) Dec 25, 2015
@ anti
I am also curious how he came to this accusation and the previous one, that I am a murderer.
What is going on in that distorted dysfunctional brain?
Vietvet
4.3 / 5 (6) Dec 25, 2015
DavidW has been banned from at least one other forum, lied about it then threatened me for exposing him.

http://phys.org/n...ion.html

AGreatWhopper
2.5 / 5 (8) Dec 26, 2015
He's one of the worst.

As to the article, Bring it!!!

jjgeibel1.8 /5 (4) Dec 22, 2015
I think that the Younger-Dryas cooling event and extinction was caused by one of these large comets


It wasn't. And, no, you don't think that, you're parroting what you think fits your a priori world view.
my2cts
3 / 5 (8) Dec 26, 2015
You have chosen pure evil. This is clear because you repeatedly refuse to uphold the truth in public as a starting point in conversation. You use the word true and truth in your posts, then provide no evidence of what these words are. Yes, all the death that is needlessly occurring is your actions being manifest thought yourself and others. A human couldn't pick a worse time to behave so childish.

Spoken like a true witchfinder general.
Now have the scum wiped off your mouth and your hands tied behind your back again.
Mayday
2 / 5 (2) Dec 27, 2015
Wouldn't there be clear evidence of the suggested recent and periodic comet fragment impacts on the moon, Mars, and Ceres to prove this centaur threat theory out? Is it there?
cjones1
2.6 / 5 (5) Dec 27, 2015
The article mentions the gravitational influence of the outer planets on the trajectory. I wonder if CMEs and solar flares exert enough influence to change a comets course, mass, or shape.
I think money has been misspent on AGW that ignore the naturally occuring factors and diverts resources that could be applied to studying influences from our solar system.
AGreatWhopper
3.2 / 5 (9) Dec 27, 2015
DavidW1 /5 (2) 6 hours ago
You have chosen pure evil. This is clear because you repeatedly refuse to uphold the truth in public as a starting point in conversation.


SFB, that's a mirror, not a computer display.
my2cts
2.7 / 5 (7) Dec 27, 2015
The article mentions the gravitational influence of the outer planets on the trajectory. I wonder if CMEs and solar flares exert enough influence to change a comets course, mass, or shape.
I think money has been misspent on AGW that ignore the naturally occuring factors and diverts resources that could be applied to studying influences from our solar system.

Fortunately it is not up the some ignoramus to decide.
Whydening Gyre
4 / 5 (4) Dec 27, 2015
I get it now...
Davidw is actually a young republican, practicing his debate skills with which to improve speeches for his future political career of baffling the masses with BS...
"It's all so clear to me now." said Dave Bowman...
Whydening Gyre
4 / 5 (4) Dec 27, 2015
This is a nice view of much that has been charted already as asterioids:
http://www.asterank.com/3d/

It would be nice to have the comets in that too.

Actually a pretty interesting link. Altho, quite capitalist in it's value list on the right.
Completely out of context with all the other crap you're regurgitating, tho.
What's up with that, Dave?
Moltvic
5 / 5 (3) Dec 28, 2015
Graham Hancock says we're all extinct by, at the very latest, 2040.
TheGhostofOtto1923
3.7 / 5 (6) Dec 28, 2015
Scary to think of what it would be like to have one hit.
I thought an asteroid 10 km(6miles) in diameter caused the dinosaur extinction. I looked on Google and found a few articles from 2013 saying it was likely a comet by the studies authors but controversial and Not decisive. Has new information supporting a comet been found?
-And they're identifying more such threats all the time. Which is why we need to spread ourselves around the solar system as quickly as possible.

If Dave the religionist were truly concerned about life he would be thinking along these terms. Life's major prerogative is to spread itself about.

The human race will survive global warming. It won't survive a comet strike. However, global warming may tax economies to the extent that colonization would be unaffordable, which is why it should have first priority.

Time to hatch. We can't wait.

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