We tend to think of our solar system as “ours,” but it’s easy to see how we’re actually just lucky enough to be in Jupiter’s cosmic neighborhood. The gas giant very likely helped shape our solar system billions of years ago, plowing through debris and dust as it moved to it’s current location near the asteroid belt, making Earth a safer place in the process. While Jupiter’s orbit has settled down, that protective role may carry on, but maybe with a bit of help. Simulations have found that Saturn seems to team up with Jupiter, and the two largest gas giants in our solar system repel or eject a fair number of comets and asteroids that might otherwise intersect with smaller planets, like Earth.
Guarded by gas giants
The idea that Jupiter’s immense size could somehow act as a shield from transiting asteroids or comets originated from an indirect reading of a study that actually focused on smaller gas planets. It was suggested that solar systems with planets no larger than Neptune would likely have more comets around, ejecting fewer objects out of their systems. That invited comparisons to our solar system with out two larger gas giants, and people started assuming that since they were bigger, they must be responsible for the relatively sparse collection of comets and asteroids nearby. The gravitational influence of something the size of Jupiter is huge, and it seemed reasonable to think that it made it into a bit of a bouncer for the solar system. NASA has even used Jupiter’s gravity to help speed up our satellites, and so less carefully aimed asteroids could easily be fired away from other planets’ orbital paths.
Simulating the effects of Jupiter and Saturn
As nice as the internal logic of this model was, it hadn’t actually been tested in any way. Without the ability to drop a few thousand comets into our corner of the universe, researchers turned to simulations to figure out what Jupiter’s bulk actually did to incoming objects. These simulations revealed that while Jupiter was important, it didn’t launch comets and asteroids on its own very consistently. It took the combined influence of Jupiter and Saturn to eject foreign objects, as neither gas giant seemed to be sufficient if the other was removed from the simulation.
A gas giant on its own isn’t without consequence though. The simulation also found that Jupiter’s gravity does a good job of slowing incoming objects down, altering their paths in the process. This means that material from these objects would actually be more likely to end up on the small, rocky planets in the inner solar system, like Earth. This scenario didn’t necessarily mean that Jupiter was putting Earth in harms way, but it might make a difference when calculating how much water on our planet may have been delivered by comets. The ice from these comets is thought to have at least partially seeded our planet with H2O, and it seems like some of them found their way here thanks to a nudge from Jupiter.
Source: Saturn Could Be Defending Earth From Massive Asteroid Impacts by Elizabeth Howell, Seeker