[SunkenCiv]

Horner's graph simulates impact rates on the Earth over a ten million year timescale. Changing the mass of Jupiter has a dramatic effect. It's not just the size or frequency of impacts that has to be taken into consideration. Speed also is an important factor. Doubling the velocity can put four times more energy into the impact.

[SunkenCiv]

"...since the 1950s..."

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[Phsstpok]

There seems to be a growing consensus that there have been a lot more and a lot more frequent impact events that was previously believed. With the Earth being mostly covered in water plus the recent understanding of air burst events all of the assumptions behind the original estimates have to be reviewed and plans changed accordingly.

Then Hollywood makes drek like Armageddon and everyone decides it’s all silly and ignores the threat again.

[Hegemony Cricket]

[SunkenCiv]

okay, I very cleverly missed this in my obviously not thorough enough search:

Jupiter Increases Risk Of Comet Strike On Earth
New Scientist | 8-24-2007 | David Shiga
Posted on 08/24/2007 4:21:38 PM EDT by blam
http://www.freerepublic.com/focus/f-news/1886116/posts

[Bernard Marx]

"In the 1950s there were only one or two near-Earth asteroids known, so they were viewed as oddities."

Giving away my age here, I remember a science fact article published in the old Galaxy SF magazine on this topic. I'm not sure of the exact date but think it was in the early 50s, written by rocket scientist Willy Ley. He raised the alarm then about the extreme dangers posed by "earth orbit-crossing asteroids," as I think he put it.

He urged an organized astronomical search for others. But I think it was the asteroid cluster that smacked into Jupiter a few years ago that truly raised the hackles of the astronomical community -- and galvanized those who believe catastrophism of that kind and more has impacted all life on earth.

[Luke Skyfreeper]

Despite the apocalyptic potential of asteroids and comets, Horner’s research suggests we’re more likely to find habitable worlds elsewhere in the galaxy. He says that the presence of a gas giant planet isn’t as important as everyone thinks, and that means there is greater wiggle room in our definition of what makes a solar system habitable. He also theorises that impacts may not always be detrimental to life -- in fact, they may be essential.

“It may be that if you have too few impacts, life will stagnate,” he says. “It may even be that our Earth is not the ideal in terms of intelligent life evolving. Maybe we have too few impacts, which is why it’s taken us four and a half billion years to get here.”