Skip to comments.Threat of Cometary Impacts may be Underestimated
Posted on 10/27/2004 7:54:44 AM PDT by cogitator
Chance Of A Cometary Impact Re-assessed
The chances of the Earth suffering a collision with a cometary body may be higher than previously thought, according to new research by astronomers Bill Napier and Chandra Wickramasinghe.
If so, international programmes designed to detect a large class of potentially threatening objects, namely near-Earth asteroids, as well as strategies to mitigate the worst effects of collisions, may be in need of urgent review.
This is the disturbing conclusion reached by the astronomers in a paper which is to be published shortly in the Monthly Notices of the Royal Astronomical Society.
Their argument is based on the known rate at which comets enter the inner solar system from the Oort cloud, a nearly spherical swarm of some 100 billion comets that surrounds the solar system out to a distance almost halfway to the Sun's nearest neighbouring star.
With about 1 percent of incoming comets ending up on relatively short-period Earth-crossing orbits, it is expected that several thousand dormant comets could be currently posing a potential threat to our planet.
Recent surveys of the Earth's immediate vicinity should have turned up some 400 such objects, whereas only a handful have so far been found.
The researchers dismiss the current belief that all the "missing" comets have disintegrated into meteor streams. If this had happened, they argue, then we should be seeing a far greater number of meteor showers and a much brighter zodiacal cloud than is observed.
They propose instead that the majority of these comets have become exceedingly black, with such low surface reflectivities that they could not be observed against the blackness of space by optical means.
Surfaces reflecting less than 0.1 percent of the incident sunlight could be formed when a comet made up of a mixture of organic grains and ices approaches the sun and sublimates, leaving an outer layer of loosely connected organic material.
Organic grains and ices? Sounds like something sold at a boardwalk food cart in California.
What's anybody gonna do about it? Me? I'm sleeping in.
Calling Ted Hamner! (lead character of the Niven/Pournelle must-read "Lucifer's Hammer")
That's it. Screw Scoresby, I'm drinking Johnny Walker Black Label from now on.
It's analogous to fighting terrorists; first you have to determine where they are and if they pose a danger before steps can be taken to take them out.
I forgot his name but read the book. Actually, I posted awhile ago (after the Columbia disaster) that one of the best justifications for an international space effort would be "Spaceguard" as described in Arthur C. Clarke's "Rendesvous with Rama". Actually, it's nicely findable with Google, so here it is:
Don't Worry! Kerry Has A Plan For This!!
> What's anybody gonna do about it?
Me, I'm resurecting circa 1961 USAF plans to station large Orion vehicles in high orbit. 4,000 ton space battleships armed with Thiokol "Sprint" booster motors with Casaba Howitzer nuke warheads are just the thing for dealing with threats like this.
It's W's fault! Tom Daschle is deeply saddened
It's W's fault! Tom Daschle is deeply saddened!
I'm not worried. Bruce Willis and Ben Afflick will be there for us if this happens.
The Orion would have to be WAY high orbit, so the EMP doesn't fry all the damn satelites.
Read Niven/Pournelle's FootFall for a fascinating look at an Orion spaceship.
Actually, between LEAP, SOHO, Catalina SkySyrvey, and a variety of other systemic sky surveys, SPaceGuard is practically here.
I remember reading an article about how a NASA geek used the finder scope on a defunct satellite to conduct some cool astronomy work. What I don't understand is why we don't do something like equipping the GPS satellites with 10" scopes. They already have a very accurate atomic clock, you could probably do some "virtual lens" work with these craft to look around the sky and find these rocks.
We need to get together, at the last minute, a team of oil-drillers. Then, we teach them how to pilot a really stupid looking shuttle, and land on the comet in question - because that's easy. THEN, we drill like a really deep hole, and put some super mega awesome 4 gigaton nuke into the comet, and like totally blow it up n' stuff. Yeah.
In all seriousness, I'd love to see some Orions up there.
But at the cost that it would take NASA to do this it would be cheaper to take the hit and try to re-establish society through the evolutionary process.
I'll be in the shower.
Small Comets and Our Origins
> The Orion would have to be WAY high orbit, so the EMP doesn't fry all the damn satelites.
You say that like it's a bad thing.
If you fry all the satellites, you have to launch all-new ones. That, coupled with the launch system market needed to launch the Orions and their support and maintenance infrastructure, will meant hat flight rate for launch systems will go through the roof, and price will plummet. This means that you will be able to launch a lot *more* satellites, as well as people, including colonists. Which means that even if the Orions fail to stop the comet, civilization will go on... just on the Moon, Mars and asteroids.
Plus... I'm unlcear that high-orbit (GEO to L4/L5) would result in meaningful EMP. EMP is a result of the Compton effect... charged particles hitting the upper ionosphere and causing a big magnetic bloom. But if the bombs are *far* away from the ionosphere, then the charged particle flux would be pretty low, and the ionosphere would not take much of a hit.
> Read Niven/Pournelle's FootFall for a fascinating look at an Orion spaceship.
Even better: Look up back issues from Volumes 1 and 2 of Aerospace Projects Review for info on the *real* Orion spacecraft designs...
> But at the cost that it would take NASA to do this ...
Who said NASA? I want the Air Force and the US Marines running this show. Soon enough, they'll transform into Fleet and Mobile Infantry....
In order to really protect from EMP, I would GUESS (SWAG) that you would have to be outside the Van Allen Belt at the very least, and preferentially beyond the Earth's magnetosphere.
As for frying all the satelites, sure, I am into planned obsolecense - new satelites in the same slots now occupied by dead satelites means more capability. Only one question: How do you clean up near-Earth space? I mean, the maintenance flights to rendezvous with the hulks, attach deorbitting engines, and sling them back to Earth is huge. Assuming that the satellites are all dead, then perhaps the best thing would be to fill near Earth space with gas (boil a few comets?), which would act to deorbit the dead ones.
Orions are still the best use for obsolete nuke weapons.
> How do you clean up near-Earth space?
The new WPA.
> sling them back to Earth is huge
Bah. Thousands of tons of metal already on orbit would be useful things to have if you plan on having space-based industry or colonization. Don't drop 'em... use 'em.
> Orions are still the best use for obsolete nuke weapons.
Nope. Orion woudl need *all* *new* nukes. Bomb-nukes are wholly inappropriate. Until you get to Really, Really Friggen GIANT Orions, you need bombs with yields of one kiloton or less. Very low yield nukes have been built (the Davy Crockett, frex), but they are incredibly filthy and wasteful, and not that reliable. Orion will need a whoel new bomb development program to produce sub-kiloton, dirt-cheapt, preferable fission-free nukes. They would also be just the thing for *other* applications. Bad guy in a cave? Fine. BOOM.
this topic is from 2004, thanks cogitator.
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