Jupiter and the solar system’s other gas giant planets may have sent water to early Earth by hurling hydrogen-rich asteroids and planetesimals into the inner solar system.
Four-and-a-half billion years ago, the solar system’s planets formed from a cloud of gas left over from the Sun’s formation. Some of that gas remained in place for several million years. As its temperature rose, hydrogen became trapped in distant, outer solar system objects.
Uranus and Neptune likely formed closer to the Sun and migrated outward, triggering impacts between objects, especially icy ones, in what became known as the Late Heavy Bombardment.
Scientists theorize Jupiter and Saturn traveled inward through the asteroid belt after forming, then changed course and headed outward, in the process sending asteroids on a collision course with Earth.
According to a computer model developed by Sean Raymond of the University of Bordeaux in France and Andre Izidoro of NASA’s Astrobiology Institute in Mountain View, California, the gas giants, as they grew and accreted more material, increased their gravitational pulls, perturbing proto-planets near them. Influenced by the remaining nebular gas, some of these carbon- and water-rich asteroids were flung into the asteroid belt between Mars and Jupiter.
“This is the best way to get these volatiles into the terrestrial planet forming region,” noted Conel Alexander, a meteorite specialist at the Carnegie Institution for Science in Washington, DC.
Significantly, Earth’s water matches that of outer solar system asteroids more than it matches that of the inner, drier asteroids.
The computer model showed three waves of icy objects sent in Earth’s direction, one that occurred when Jupiter swelled up, another when Saturn did so, and a third when Uranus and Neptune migrated inward only to be blocked by Jupiter and Saturn and sent back int the outer solar system.
Because this model indicates that in the process of formation, any gas giants would send water-rich material inward toward their star’s habitable region, it could help scientists find watery exoplanets.
“I think the coolest thing is that it basically implies for any exo-solar system where you have giant planets and terrestrial planets, those giant planets would send water inward to the terrestrial planets,” said David O’Brien of the Planetary Science Institute (PSI) in Tucson, Arizona.
“That opens up a lot of possibilities for habitable planet studies.”
A paper on the study has been published in the journal Icarus.