Wandering Jupiter May Have Rebooted The Entire Inner Solar System
A new theory shows that Jupiter may have briefly visited our inner solar system, decimating what was there and setting the stage for the formation of the inner rocky planets that we know and love.
This comes from a paper in the journal, Proceedings of the National Academy of Sciences called “Jupiter’s decisive role in the inner Solar System’s early evolution”
You may think that our solar system, at least from a big-picture perspective, is fairly standard compared to other solar systems. We basically have big gas giants at the outskirts and small rocky worlds closer in.
Statistically speaking, though, we’re a bit anomalous. We have, after all, found over 500 solar systems the past couple of decades with multiple planets in them. Many of these are populated by massive planets insanely close to their parent star, closer than Mercury. For example, early on in our search we ran into the so-called Hot Jupiters (also called Roaster Planets). These are gas giants like Jupiter or Saturn that are very hot because they orbit anywhere from a 100th to 1/2 half of earth’s distance from the sun.
We’ve also encountered many super earths out there. These are not necessarily earth-like in any way except that they are more massive than earth, but not as heavy as our smallest gas giant, Uranus. These super earths are also inhospitably close to their parent stars and they have a thick hydrogen-rich envelope surrounding them. In fact, some suggest calling the biggest super earths, gas dwarfs to reflect their similarity to our gas giants.
So these other systems not only have massive planets close to their star, many have a lot of hydrogen. Our inner planets, however (Mercury, Earth, Venus, Mars) are relatively small and are hydrogen poor. Why such a glaring difference?
This is the question that this new model attempts to address. If this theory is correct, the order of events could have gone something like this:
- Jupiter forms first before all other planets
- It moves towards the sun due to tidal interactions with the nearby gas
- This could have brought it from 3 AU all the way to 1.5 AU from the sun
- Then Saturn forms
- Through a series of complicated gravitational interactions, Saturn brings Jupiter back to its current orbital distance of 5.2 AU
Jupiter’s back and forth journey essentially wreaks havoc within the inner solar system. Planetesimals at that time would have their orbits shifted, causing a cascade of collisions which would send much of the debris into the sun instead of coalescing into future super earths. Jupiter would have also apparently mopped up any of the hydrogen in the environment.
This model requires then, a special scenario in which two gas-giants form first, the outer one (Saturn) being less massive than the inner one (Jupiter). This leads to the complex scenario which created our modern inner solar system.
The paper’s abstract says it well:
“The Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.”
This appears to potentially be a neat little solution to the mystery of why our inner planets are low mass and low in hydrogen compared to others that we’ve examined.
I would like to officially thank Jupiter (and Saturn) for everything they’ve inadvertently done for us.
Image Credits: https://en.wikipedia.org/wiki/Solar_System
Hot Jupiter: http://scitechdaily.com/hubble-reveals-the-puzzling-properties-of-hot-jupiter-atmospheres/
Super Earths: NASA/Ames/JPL-Caltech