Tiny comet grain dates Jupiter’s formation
A study by researchers from the University of Hawaiʻi at Mānoa’s Hawaiʻi Institute of Geophysics and Planetology found that particles from comet 81P/Wild 2 brought to Earth in 2006 by NASA’s Stardust spacecraft indicate that Jupiter formed more than three million years after the formation of the first solids in the solar system.
The new finding helps test solar system formation theories, which do not agree on the timing of Jupiter though it is certain the formation of this giant planet affected how materials moved, collided and coalesced during the complex planet-forming process.
Ryan Ogliore, a HIGP postdoctoral researcher, conducted the study with Researcher Gary Huss and Specialist Kazuhide Nagashima and colleagues from the University of California at Berkeley, University of Washington and the Lawrence Berkeley National Laboratory. The results were published in the February 1, 2012 issue of The Astrophysical Journal Letters.
Comets formed in the frigid Kuiper belt out beyond Neptune, but analyses of the Wild 2 samples showed that comets are composed of low-temperature and high-temperature materials that must have come from completely different environments.
The team analyzed a chondrule fragment known from previous research to have formed by high-temperature processes in the inner solar nebula—the cloud of gas and dust surrounding the infant Sun from which the planets formed. What could be more contradictory than high-temperature objects from the innermost regions near the Sun becoming the predominant dust components of an icy comet in the outer solar nebula? Ogliore and colleagues set out to determine when this grand, outward migration of materials occurred.
Their results suggest the fragment formed at least three million years after the first solids formed.
“We were surprised to find such a late-forming, high-temperature little rock in these cometary samples,” said Ogliore. “That we are able to test theories about the formation time of Jupiter and consequently, the origins of our Solar System is really a testament to the importance of sample-return missions like Stardust.”