When Did the Solar Nebula Form?
By looking at the content of chondrules and Calcium Aluminum- rich inclusions (CAIs), both components of the primitive meteorite Allende, Lab physicist Ian Hutcheon, with colleagues from the University of Hawaii at Manoa, the Tokyo Institute of Technology and the Smithsonian Institution, found that the age difference between the two fragments points directly to the lifetime of the solar nebula. CAIs were formed in an oxygen-rich environment and date to 4.567 billion years old, while chondrules were formed in an oxygen setting much like that on Earth and date to 4.565 billion, or less, years old.
"Over this span of about 2 million years, the oxygen in the solar nebula changed substantially in its isotopic makeup," Hutcheon said. "This is telling us that oxygen was evolving fairly rapidly." The research appears in the April 21 edition of the journal Nature.
"By the time chondrules formed, the O-16 content changed to resemble what we have on Earth today," Hutcheon said.
In the past, the estimated lifetime of the solar nebula ranged anywhere from less than a million years to 10 million years. However, through analysis of the mineral composition and oxygen and magnesium isotope content of CAIs and chondrules, the team was able to refine that time span to roughly 2 million years.
"In the past the age difference between CAIs and chondrules was not well-defined," Hutcheon said. "Refining the lifetime of the solar nebula is quite significant in terms of understanding how our solar system formed."