Saw a program on Discovery channel (or other) a while back. They were talking about several characteristics of the Earth that made life come together. Several made sense, such as a sun, a moon of approriate size, a slight tilt of the poles, water, etc. One of the things they mentioned was that having a large planet like Jupitor in our solar system reduced the number of large meteors that have hit us.
Sounds fishy to me. Jupitor may be huge compared to the Earth, but compared with the area of our Solar System, it’s negligable.
Anybody know if this is accepted scientific wisdom?
I don’t know if it is a deciding factor, but the reasoning makes sense, so it certainly wouldn’t hurt if Jupiter attracted all of the meteors away from the Earth.
I think what you’re saying is that even Jupiter is incredibly small when compared to the rest of the solar system. And when you look at it that way, it makes sense - if you were on an out-of-control spaceship heading into the solar system, the worry of crashing into a planet would be very small.
However, there’s another way to think of it. Comets orbit the sun, crossing the paths of several planets, for mellennia. They keep doing it until eventually they smash into a planet by chance. The chance of hitting Jupiter is small on any orbit, but over millions of orbits, it’s much more likely to catch a comet than is Earth.
Jupiter isn’t the only gas giant in our solar system, we have four. Granted Jupiter is the largest, but with all four giant planets usually in different places in their orbit, It should act much like a screen, snagging much of the random space debris in their respective gravities.
Perhaps, but wouldn’t a large gravity well also nudge the orbits of planetessimals that would otherwise have missed Earth, into orbits that intersected Earth’s? Not all objects that are affected by the gravity of Jupiter necessary impact the Jovian surface. I would say a much larger percentage are simply moved out of stable orbits into more erratic ones that cause them to begin to fall towards the sun, thus crossing Earth’s orbit; I think it could be argued that the existence of Jupiter could increase the number of impacts on Earth. Likely? Unlikely? Just my 2¢ worth.
TT
“It is better to know some of the questions than all of the answers.”
–James Thurber
Jupiter may be relatively small in comparison to the size of its orbit, but its gravity well stretches out a long, long way. And we’re talking about comets coming and going over billions of years. It doesn’t have to sweep very many per year before it gets a goodly percentage of the debris left over from the solar system’s formation.
On the other hand, recent observations suggest that most planetary systems have large gas giants like this in them.
Just thought I’d also throw in that, as far as I know, one of the main theories on the formation of the asteroid belt is that, instead of a planet forming at that distance from the sun, Jupiter’s gravity disrupted the orbit of matter in that zone enough so that the matter was unable to “accumulate” into a planet.
Some (relatively few, as far as I know) asteroids cross earth’s orbit, and I can imagine that Jupiter’s gravity would play a part in that.