Posted on 08/04/2009 10:30:30 AM PDT by BGHater
Comet strikes are an unlikely cause of past mass extinctions on Earth, according to computer simulations.
Scientists used the simulations to model the paths of long-period comets, to determine the likelihood of these "dirty snowballs" striking our planet.
The University of Washington, Seattle, research appears in Science journal.
How many mass extinctions in Earth's history were caused by these icy bodies crashing into our planet has been a subject of considerable debate.
Many scientists agree that an asteroid strike 65 million years ago wiped out the dinosaurs. But there is uncertainty about how many other such events were triggered by asteroid or comet colliding with Earth.
Comets are composed of dust, rock, water ice and frozen gases. When their orbits bring them into close proximity with the Sun, parts of them warm up, causing material to sublimate (turn directly from a solid to a gas state) and form a "fuzzy" envelope around the comet nucleus.
Asteroids are distinguished from comets precisely because they lack this envelope, or "coma".
Comets 'acquitted'
Halley's comet - which reappears in our sky every 75 years - is described as "short period". This type of comet originates in a region of our Solar System called the Kuiper Belt.
So-called "long period" comets are thought to come from the more distant Oort Cloud.This is a large area of debris left over from the formation of the Solar System some 4.5 billion years ago.
The outer part of this Oort Cloud region was previously thought to be a source of long-period comets that pass close to Earth.
Their orbits are thought to change when they are nudged by the gravity of a nearby star.These events are thought to trigger an increase in the frequency of comets entering the inner Solar System-a phenomenon called "comet showers".
(Excerpt) Read more at news.bbc.co.uk ...
Don’t blame ME[Mass Extinction] ping.
And we all know that computer simulations are always accurate. Especially about climate.
Sorry, but this kind of “scientific” statement, in the face of comet crashes seen on Jupiter that are larger than planet Earth, is pathetic....
Dude. I’m going to be pissed if this say it’s not a comet it was an asteroid. There’s probably a diff there, but not to me!
“Comet strikes are an unlikely cause of past mass extinctions on Earth, according to computer simulations.”
Based on quite incomplete information.
No one knows either the number of comets in the Oort Cloud, or how the perturbations work that sometimes cause them to fall towards the inner solar system.
What we do know is that they are some of the highest speed objects that might strike the Earth, and they’re impossible to predict or identify in advance. A few months (or at best, years) warning is all you get...
We also have no way of knowing about more exotic objects, like brown dwarfs or small black holes. One of those could wander into the system at any time as well.
They are exonerating the comets so that they can blame the extinctions on George W. Bush.
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