Jupiter, destroyer (and savior) of worlds

It has long been known that the advanced life on Earth may owe its existence to Jupiter, whose hulking presence and massive gravity well have probably saved our planet from many an asteroid collision. Not only has Jupiter attracted and destroyed asteroids that may otherwise have collided with Earth, but it has also flung asteroids entirely out of our solar system. Jupiter is the great guardian, protecting our little planet from the sort of repeated collisions that would have set back the development of life over and over again.

Now two scientists are postulating that Jupiter (and Saturn, in a secondary role) may be responsible for the very existence of Earth itself—because it destroyed the first generation of planets in the inner system, leaving a debris ring that later formed a second generation farther from the sun.

In the last two decades, planet-hunting has reached new heights, and astronomers have studied nearly 2,000 planets in other systems. It turns out that our system is pretty weird.

The typical planetary system is made up of a few super-Earths — rocky planets up to 10 times the mass of Earth — orbiting much closer to their stars than Mercury does the sun. These super-Earths are usually not only rich in rock, but also in so-called volatile materials that easily vaporize when heated.

This means that super-Earths “tend to have very thick and massive atmospheres with pressures that exceed that of the Earth by factors of hundreds, if not thousands,” lead study author Konstantin Batygin, a planetary scientist at the California Institute of Technology in Pasadena, told Space.com. In comparison, “the atmospheres of our terrestrial planets are exceptionally thin.”

Moreover, planetary systems that possess giant planets similar to Jupiter and Saturn typically have them much closer to their stars than in the solar system. Giant worlds known as hot Jupiters, whose orbits are only about one-tenth of the distance from Mercury to the sun, are some of the alien worlds that scientists have seen most often.

In attempting to explain the anomaly that is us, Batygin and co-author Gregory Laughlin gamed out a scenario called the Grand Tack. In this version of our early solar system, Jupiter formed, then migrated in toward the sun. There, its massive bulk and gravity destroyed the first generation of smaller, rocky planets—the ones orbiting extremely close to the sun, where the inferno of heat would have precluded the formation of any advanced life as we know it.

Once Saturn formed, it drew Jupiter back out, leaving the shattered remnants of those early super-Earths to reform into the second generation of inner planets. These were much farther out than the first, since the bulk of the debris ring closer to the sun would have spiraled in and been vaporized. Because they formed later, farther from the sun, and from a different set of material than their predecessors…

This would explain why Mercury, Venus, Earth and Mars are younger than the outer planets, and why they are both smaller and have much thinner atmospheres than inner worlds seen in other planetary systems.

Jupiter and Saturn have always fascinated me due to their size, beauty, and the awesomeness of their satellites, but now I have a whole new reason. They might be responsible for us.