Ultraviolet shines light on origins of the solar system

 

By analyzing the oxygen isotopes (varieties of a part that have some extra neutrons) of those refractory inclusions, the research team has determined that the differences in composition between the sun, planets, and other system materials were inherited from the protosolar molecular cloud that existed even before the system. The results of their study are recently published in Science Advances.

"It has been recently demonstrated that variations in isotopic compositions of the many elements in our system were inherited from the protosolar molecular cloud," said lead author Alexander Krot, of the University of Hawaii. "Our study reveals that oxygen isn't an exception."

Molecular cloud or solar nebula?

When scientists compare oxygen isotopes 16, 17, and 18, they observe significant differences between the world and also the sun. this can be believed to result in processing by ultraviolet of CO, which is broken apart resulting in an outsized change in oxygen isotope ratios in water. The planets are formed from dust that inherits the changed oxygen isotope ratios through interactions with water.

What scientists haven't known is whether or not the ultraviolet processing occurred within the parent molecular cloud that collapsed to create the proto-solar system or later within the cloud of gas and dirt from which the planets formed, called the solar nebula.

To determine this, the research team turned to the foremost ancient component of meteorites, called calcium-aluminum inclusions (CAIs). They used an ion microprobe, electron backscatter images, and X-ray elemental analyses at the University of Hawaii's Institute of Geophysics and Planetology to carefully analyze the CAIs. They then incorporated a second isotope system (aluminum and magnesium isotopes) to constrain the age of the CAIs, making the connection -- for the primary time -- between oxygen isotope abundances and mass 26 aluminum isotopes.

From these aluminum and magnesium isotopes, they concluded that the CAIs were formed about 10,000 to 20,000 years after the collapse of the parent molecular cloud.

"This is extremely early within the history of the scheme," said Lyons, who is an associate research professor at ASU's School of Earth and Space Exploration, "so early that there wouldn't be enough time to change oxygen isotopes within the solar nebula."

Although more measurements and modeling work are needed to totally assess the implications of those findings, they are doing have implications for the inventory of organic compounds available during the scheme and later planet and asteroid formation.

"Any constraint on the number of ultraviolet processing of fabric within the solar nebula or parent molecular cloud is crucial for understanding the inventory of organic compounds that result in life on Earth," Lyons said.