The protosun evolved in a hot nebula of infalling gas and dust that formed an accretion disk (green) of surrounding matter. Visible and ultraviolet light poured from the sun, irradiating abundant clouds of carbon monoxide, hydrogen sulfide, and other chemicals. Temperatures near the sun were hot enough to melt silicates and other minerals, forming the chondrules found in early meteoroids (dashed black circles). Beyond the snowline (dashed white curves), water, methane, and other compounds condensed to ice. Numerous chemical reactions contributed to the isotopic ratios seen in relics of the early solar system today. Credit: University of California at San Diego, Lawrence Berkeley National Laboratory

Searching for the solar system’s chemical recipe

February 20, 2013 by Paul Preuss

(—By studying the origins of different isotope ratios among the elements that make up today’s smorgasbord of planets, moons, comets, asteroids, and interplanetary ice and dust, Mark Thiemens and his colleagues hope to learn how our solar system evolved. Thiemens, Dean of the Division of Physical Sciences at the University of California, San Diego, has worked on this problem for over three decades.

In recent years his team has found the Chemical Dynamics Beamline of the Advanced Light Source (ALS) at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to be an invaluable tool for examining how photochemistry determines the basic ingredients in the solar system recipe.

“Mark and his colleagues Subrata Chakraborty and Teresa Jackson wanted to know if photochemistry could explain some of the differences in isotope ratios between Earth and what’s found in meteorites and interplanetary dust particles,” says Musahid (Musa) Ahmed of Berkeley Lab’s Chemical Sciences Division, a scientist at the Chemical Dynamics Beamline who works with the UC San Diego team. “They needed a source of ultraviolet light powerful enough to dissociate gas molecules like carbon monoxide, hydrogen sulfide, and nitrogen. That’s us: our beamline basically provides information about gas-phase photodynamics.”

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