Hypothesis: Our Solar System Lacks 'Super-Earths' Because Jupiter Wrecked Them All

I’ve always loathed Jupiter.

For one thing, I am not stoked on toxic gases or crushing gravity. And the weather on Jupiter is abysmal, with wind speeds roughly twice those of hurricanes on Earth.

Were I in charge, I once told a theoretical physicist at Vanderbilt University in Nashville, I would set about destroying Jupiter for the good of humanity. He reminded me that in 1994, a like-minded comet smashed into the gas giant, which is some 89,000 miles across. The result was like a bullet fired into a mountain of shaving cream, accomplishing nothing.

Sometimes when I am feeling crabby aboard an overly humid BART car with no vacant seats I think, “Well, of all the places in the universe that I could be right now, at least I’m not on Jupiter.”

I mention this to explain the vindication I feel upon learning that Jupiter may be the reason our solar system is, it’s turning out, something of a weirdo among its galactic peers. Scientists perusing thousands of exoplanets (some potentially habitable) in other systems around the Milky Way are discovering that rocky “super-Earths” are commonplace.

These are planets bigger than our own, albeit perhaps not better for our brand of life: they may have crushingly thick atmospheres, and their orbits are typically tighter than Mercury’s.

“The standard-issue planetary system in our galaxy seems to be a set of super-Earths with alarmingly short orbital periods. Our solar system is looking increasingly like an oddball,” says Gregory Laughlin, professor and chair of astronomy and astrophysics at University of California,  Santa Cruz, and co-author of a new paper in Proceedings of the National Academy of Sciences.

The reason our humble solar system suffers this peculiar dearth of “super-Earths” and must instead make do with our vanilla “Earth-Earth” can be summarized thusly: Jupiter.

Like Miley Cyrus, Jupiter came in like a wrecking ball.

In 2011, astronomers proposed the “Grand Tack” hypothesis, suggesting that during the early days of the solar system — the first few million years — Jupiter migrated inward toward the sun, stopping only when the formation of Saturn tugged it back out to its current orbit.

Laughlin and co-author Konstantin Batygin think rocky planets could’ve been forming near our sun, until an encroaching Jupiter’s gravitational perturbations rudely started compressing their orbits, slinging them into each other in a chain reaction that took out any nascent super-Earths and sent a lot of debris spiraling into the sun to be vaporized.

“It’s the same thing we worry about if satellites were to be destroyed in low-Earth orbit. Their fragments would start smashing into other satellites and you’d risk a chain reaction of collisions,” Laughlin says. “Our work indicates that Jupiter would have created just such a collisional cascade in the inner solar system.”

A second generation of inner planets including familiar old Earth, as well as Mercury, Venus and Mars, would’ve emerged from the aftermath only tens of millions of years later. This explains why the planets close to our sun are younger than the planets farther away. And again, this was possible only thanks to Saturn tugging Jupiter away, thereby allowing our humble planet some breathing room to, you know, exist.

Thank you, Saturn.