Rethinking Jupiter

Astrobio.net ^ | Monday, November 12, 2007 | Lee Pullen

[SunkenCiv]

Without Jupiter acting as a "cosmic vacuum cleaner" sucking up these dangerous objects, there would be so many catastrophic impacts that life probably wouldn't have evolved on the Earth and we wouldn't be here today... "This vacuum cleaner idea goes back to when the long-period comets coming in from the Oort Cloud were viewed as being the only significant impact risk," says Horner. "In the 1950s there were only one or two near-Earth asteroids known, so they were viewed as oddities." ...Since the 1950s, scientists have discovered more objects in the solar system, and they say many of them could collide with us.

[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]

[roaddog727]

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

Armageddon was indeed melodramatic drek. Deep-impact, was much better.

However, you’re absolutely right Making the gen-po think it’s all silly.

[P8riot]

While Jupiter’s gravity could very well deflect or otherwise modify the trajectory of these Near Earth Objects, thus preventing their impact on Earth, could it not also deflect an otherwise benign object directly into our path?

[SunkenCiv]

I doubt that enough people saw Armageddon and saw enough wrong with the non-science in it to come to that conclusion. It won’t be long, though, before some idiot, moron, or jackass comes along and puts “CALLINGARTBELL” in the keywords — and that’s due to an attitude that keeps some people from seeing Armageddon or Deep Impact in the first place.

[SunkenCiv]

That’s the idea. Also, there’s enough crud in the general vicinity of Earth that, over time, most of the known impacts, including major ones, could have been caused by stuff that is nearby. For a rough analogy, think about the toy from the 1960s, the Spirograph.

[RightWhale]

There have been a lot of cosmic impacts. Look at the moon. But, the incidents have dropped off lately. Most of the harsh stuff has already happened.

[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

[Eaker]

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

Are you saying that Bruce Willis really didn't really fly a titanium shuttle to an asteroid and blow it up?

So the movie was just for entertainment purposes?

Well the Asteroid Threat Level at the Eaker Compound just went up and off of the chart!

BTW, if you want drek go rent Reign on Me and let me know if you don't think that Adam Sandler owes you two hours of your life back.

[Phsstpok]

While Jupiter’s gravity could very well deflect or otherwise modify the trajectory of these Near Earth Objects, thus preventing their impact on Earth, could it not also deflect an otherwise benign object directly into our path?

Clearly, but the math makes it hugely more likely that any deflection would be onto a path that doesn't intercept Earth than one that does.  After all, there are so many more paths that don't hit us than the limited set of paths that do.  But it's still possible.

I have a spread sheet that I pull up every time a new Earth orbit crossing NEO is spotted and the odds of it hitting us are bandied about.  I take our orbital radius and uses that to calculate our orbital circumference.  From there I divide it by 365 days to get how fast the Earth is moving in our orbit.  I use that to calculate how many minutes, hours, days, etc. the calculated path of the NEO needs to be off for them to be wrong about said objects hitting us or not.  Usually it's pretty big, but a few times it's been a matter of a few minutes off for a prediction that's years away, making a really tiny error have potentially big impact (pun intended).  And the guys who usually make the most certain statements about such things are the same guys who forgot to convert from from meters to feet and sent the Mars probe straight into the planet instead of into an orbit.  Ooopsy.

[bert]

Also, as it attracts objects, it grows. As it grows it’s attraction of earth increases. A growing Jupiter and a burning sun mean earth is moving away from the sun and towards Jupiter......

Result, global cooling.

[Phsstpok]

I thought Deep Impact was a pretty good movie. Even their dramatic license for plot purposes were relatively tolerable. I particularly liked them using a Project Orion nulear explosion pulse rocket for the ship. Larry Niven and Jerry Pournelle used one in their 1970s novel Footfall.

This is the description of launch (it took off from the ground in their novel) from folks hiding in a bomb shelter:

The sound of the end of the world slammed against the ceiling, For a moment that incredible crowd was totally silent. Then it came again:
SLAM.
Commander Kennedy whooped. "They made it! They're up! It's—"
SLAM
"—first bomb fails you just start over."
SLAM
"If the second bomb fails, you're already—"
SLAM
"—already in the air. You'll fall. They're on their—"
SLAM
"—way, by God! You can give me that drink now."
SLAM

And the folks riding on top of the ship

God was knocking, and he wanted in bad.
WHAM
WHAM
WHAM
quiet
"The respite will be brief," Gillespie bellowed. Harry barely heard him in the silence after the bombs. How many were there? Twenty? Thirty?

I love the first line in the second bit.

[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.”

[SunkenCiv]

That was 1994’s comet Shoemaker-Levy 9, actually comets, as an earlier encounter with Jupiter apparently had busted one comet into multiple comets. :’)

[SunkenCiv]

:’)

[SunkenCiv]

“From there I divide it by 365 days”

shouldn’t that be more like 365.242198? ;’)

[SunkenCiv]

I saw both of them, I guess that was the same year of release? Anyway, “Armageddon” had IMHO a stronger plot, but the trappings were all completely screwed up — the trip around behind the Moon wouldn’t have worked and was stupid; there was no way to refuel at Mir; the “just in time” explosion was ludicrously transparently overdramatic. “Deep Impact” was better in the setup than it was in the denouement (again, IMHO), but also had Tea Leoni. Unfortunately, it had a sappy Spielberg ending.