Ultraviolet shines light on origins of the solar system

Date:
October 20, 2020
Source:
Arizona State University
Summary:
In the search to discover the origins of our solar system, an
international team including planetary scientists has compared
the composition of the sun to the composition of the most ancient
materials that formed in our solar system: refractory inclusions
in unmetamorphosed meteorites.



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


==========================================================================
"It has been recently demonstrated that variations in isotopic
compositions of many elements in our solar system were inherited from
the protosolar molecular cloud," said lead author Alexander Krot, of
the University of Hawaii. "Our study reveals that oxygen is not the
exception." Molecular cloud or solar nebula? When scientists compare
oxygen isotopes 16, 17 and 18, they observe significant differences
between the Earth and the sun. This is believed to be due to processing
by ultraviolet light of carbon monoxide, which is broken apart leading
to a large 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 have not known is whether the ultraviolet processing
occurred in the parent molecular cloud that collapsed to form the
proto-solar system or later in the cloud of gas and dust from which the
planets formed, called the solar nebula.

To determine this, the research team turned to the most 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 first 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 in the history of the solar system," said Lyons,
who is an associate research professor at ASU's School of Earth and Space Exploration, "so early that there would not be enough time to alter oxygen isotopes in the solar nebula." Although more measurements and modeling
work are needed to fully assess the implications of these findings, they
do have implications for the inventory of organic compounds available
during solar system and later planet and asteroid formation.

"Any constraint on the amount of ultraviolet processing of material in the solar nebula or parent molecular cloud is essential for understanding the inventory of organic compounds that lead to life on Earth," Lyons said.


========================================================================== Story Source: Materials provided by Arizona_State_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Alexander N. Krot, Kazuhide Nagashima, James R. Lyons, Jeong-Eun
Lee,
Martin Bizzarro. Oxygen isotopic heterogeneity in the early Solar
System inherited from the protosolar molecular cloud. Science
Advances, 2020; 6 (42): eaay2724 DOI: 10.1126/sciadv.aay2724 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201020105553.htm

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