Jupiter is responsible for both enabling and organizing the architecture of our inner solar system, as well as creating the conditions necessary for Earth’s own formation, say the authors of a new paper appearing in the journal Science Advances.
Our massive gas giant planet’s 11.5-year solar orbit has long been known to be somewhat anomalous among the thousands of extrasolar planetary systems that we have been capable of observing thus far.
But the team’s computer models in this new study put an unexpected twist on the timing and influence Jupiter had in creating the architecture of our early inner solar system. Jupiter’s early growth within 1.5 million years after the birth of our solar system, some 4.56 billion years ago, directly influenced where the building blocks of Earth and other terrestrial planets accumulated.
By depleting gas from the inner Solar System, Jupiter helped preserve solids in the region we now call the habitable zone, Baibhav Srivastava, a graduate student in planetary science at Rice University in Houston and the paper’s lead author, tells me via email.
Our results suggest that the timing of Jupiter’s formation was crucial for keeping Earth’s ingredients at the optimal location, where they could combine and grow, Srivastava tells me. In that sense, Jupiter’s early formation may have been one of the key factors that made a life-bearing planet like Earth possible, he says.
Rocky Planet Formation
Jupiter’s early growth reshaped the solar system’s evolution and set the stage for the formation of rocky planets, says Srivastava. While terrestrial planets themselves took tens to hundreds of millions of years to reach their final sizes, their building blocks (planetary embryos) formed within the first few million years, he says.
In a gas-rich planetary disk, the building blocks of the terrestrial planets would otherwise have spiraled inward and been lost because of the effects that the gas exerts on the objects, says Srivastava. But Jupiter’s presence and its induced “bumps on the road” prevented that from happening, he says.
How Did It Work?
Jupiter’s immense gravity sent ripples through the newborn solar system’s disk, creating “cosmic traffic jams” that prevented small particles from spiraling into the Sun, Rice University notes. Instead, these particles collected into dense bands where they could clump together into planetesimals — the rocky seeds of planets, says the university.
As Jupiter grew—around 1.5 million years after the solar system’s birth—it opened a deep gap in the solar nebula, disrupting the inward flow of pebbles and dust, says Srivastava. This barrier delayed the supply of solid material to the inner solar system, he says.
What does all this tell us about our place in the galaxy?
By depleting the gas from the inner Solar System, Jupiter created the conditions that allowed rocky planets to form and remain in orbits relatively farther from the Sun, unlike the compact, close-in “super-Earths” that we often see in other planetary systems, says Srivastava.
A Unique Solar System?
If Jupiter had formed much later, after about 2 million years, the growing planets would have spiraled inward toward the Sun, resulting in a system of close-in super-Earths rather than relatively widely spaced terrestrial planets, says Srivastava.
As for planetary systems without such Jupiter-like planets?
Planetary systems that lack an early-forming Jupiter, or that have a giant planet that forms too late, may still form rocky planets, says Srivastava. But those planets are likely to be larger, hotter, and orbit much closer to their stars than those in our Solar System, he says.
The Bottom Line?
Jupiter didn’t just become the biggest planet — it set the architecture for the whole inner solar system, Rice University planetary scientist Andre Izidoro, the paper’s second author, says in a statement. Without it, we might not have Earth as we know it, he says.