Without Jupiter, primitive Earth might have drifted too close to the sun, rendering it incapable of hosting life, a study from Rice University in Houston reveals.
That's one potential interpretation from new research that started with another curiosity: Scientists have long wondered why the earliest solid objects in the solar system didn't all form at the same time. Evidence from meteorites, the rocky space debris that falls to Earth, shows two distinct generations of these planet-building supplies. Though the first group formed quickly, within the first million years, the second group, which produced the rocky blocks closer to Earth, Mars, and Venus, didn’t form until 2 or 3 million years later. How enough dust remained to make this second wave of material, though, has been a mystery.
To find out, researchers ran detailed computer simulations of the young solar system. The results, which appear in the journal Science Advances, point to Jupiter — whose mass today is more than double that of all the other planets combined — as the key player. Prior to this study, a model didn't exist that could fully account for the age gap in the ancient planet-building material. This research may be the first to combine how Jupiter grew, dust moved, and asteroids formed into one explanation.
Not only did the gas giant play a pivotal role in keeping Earth and its neighbors from migrating more inward, but it probably stunted their growth, too, cutting off their access to material from the outer part of the solar system, said Baibhav Srivastava, a planetary scientist and one of the study's authors.
"Our Earth might have become a 'super-Earth,'" Srivastava told Mashable. "This may have significant implications for the potential habitability of Earth as well, since it may have left the 'Goldilocks' zone of the solar system."
The so-called Goldilocks zone refers to the region in space around a host star that isn't too hot or cold, allowing liquid water to exist on a planet's surface.
Many scientists call Jupiter the architect of the solar system because its immense gravity influenced the orbits of other planets and carved up the gas and dust from which they all emerged. This celestial neighborhood is about 4.5 billion years old.
As the giant planet grew, it reshaped the sun's surroundings, according to the study. It drained gas from the inner region and created ridges of higher pressure that effectively fenced in dust and formed ring-like clumps of material. These "dust traps" allowed new solid objects to form long after the original ones, naturally explaining the age gap of the rocky space material. The timing of this second wave matches that of ordinary chondrites, the most commonly found type of stony meteorite on Earth.
Scientists have estimated the ages of meteorites' parent bodies by measuring tiny amounts of isotopes, particular forms of elements, inside them. Because some isotopes are radioactive, they slowly change into other elements at a predictable rate. By comparing how much of the original isotope remains to how much has decayed, researchers can calculate when the rock solidified. It's similar to carbon dating ancient bones or wood on Earth, but with heavier elements, such as lead, rubidium, and strontium, Srivastava explained.
By the time the second generation of rocky material solidified, Earth was already forming, so they likely didn't contribute much to the planet.
But the model supports the idea that Jupiter's birth must have come extremely early, within the first 2 million years of the solar system. That gave the young planet time to shape and structure the rest of the available gas and dust around the sun.
The findings mirror what astronomers now observe with powerful telescopes in other emerging star systems, said André Izidoro, a Rice assistant professor and author of the study.
"Looking at those young disks, we see the beginning of giant planets forming and reshaping their birth environment," Izidoro said in a statement. "Our own solar system was no different. Jupiter’s early growth left a signature we can still read today, locked inside meteorites that fall to Earth."
