Dating Presolar Grains: A Tale Older Than Time

Presolar grains
Image credit: Philipp R. Heck, Jennika Greer, Levke Kööp, Reto Trappitsch, Frank Gyngard, Henner Busemann, Colin Maden, Janaína N. Ávila, Andrew M. Davis, and Rainer Wieler

How did our solar system form and what are the components that ultimately led to the current chemical makeup of our little piece of cosmic real estate? The lyrics “we are stardust, we are golden, we are billion-year-old carbon” have been refined since Joni Mitchell wrote this song in 1970. In a recent study from the University of Chicago, the carbon we are made of could be as much as 7 billion years old. Philipp Heck and colleagues looked at silicon carbide grains in a primitive carbonaceous chondrite meteorite named Murchison and found that these grains might have been traversing the galaxy for longer than previously thought. These tiny, micrometer-sized grains have geochemical characteristics that preclude their formation in our own solar system and lead the team to conclude they formed in previous generations of stars, predating our own Sun’s formation.

When and where are these grains coming from and what does that tell us about our galactic neighborhood? The authors argue that their findings corroborate other research which indicates there was a period of enhanced star formation which occurred approximately 7 billion years ago. During this period, specific types of stars several times larger than our Sun were dying and producing presolar grains. These grains were blown off the star and made their way through the cosmos until they were incorporated into the primitive chondrite material that was just forming in our solar system. Primitive chondrites are key pieces for understanding the materials that created our asteroids and rocky planets. READ MORE