October 15, 2013

Professor Karen Castle's quantum cascade laser (left) emits a beam that is directed through optics into a reaction chamber (right). Measurements are displayed on the screen behind Castle.

By Matt Hughes

LEWISBURG, Pa. — Inside a lab at Bucknell's Rooke Science Center, Professor Karen Castle is working to unlock the secrets of the Martian atmosphere, some 35 million miles from Lewisburg and the rest of the blue planet.

Castle, a chemistry professor, has been awarded a $178,000 grant from NASA's Mars Fundamental Research Program to undertake a three-year study related to Mars' middle and upper atmosphere. Her research will aid a community of scientists, including NASA researchers, trying to understand the climate of the red planet, and will give scientists a better understanding of our own atmosphere on Earth.

"The Martian atmosphere is significantly different from ours," Castle said. "But there are some similarities in the chemical and physical processes in the upper atmospheres of both planets."

Castle's research will focus on carbon dioxide, which comprises 95 percent of the Martian atmosphere. The atmosphere of Mars is dominated by heating and cooling processes involving CO2, and Castle's research will measure rates of energy transfer as vibrationally excited CO2 molecules collide with other atmospheric molecules and atoms. The results will help NASA improve existing Martian climate models.

"Creating accurate models of both the Martian atmosphere and Earth's atmosphere can shed light on a wide variety of important applications such as satellite orbital longevity and global climate change," Castle said.

"The net result of CO2 cooling in Earth's upper atmosphere is that an object in low Earth orbit is going to stay up longer, which could be a good thing or a bad thing depending on what you're after," she continued. "It's a good thing if you have an orbiting satellite that you want to keep taking data; it's a bad thing if you have space debris, because now it's just hanging out longer than it should."

Understanding energy transfers to more accurately model the atmosphere can also give scientists a clearer picture of terrestrial processes like climate change, Castle observed.

"A small change in temperature due to increased greenhouse gases here at the surface of the Earth is a large change in the middle atmosphere, so it's a much more sensitive way to monitor global climate change," Castle said. "But in order to exploit that we have to characterize that region of the atmosphere really well, and it's hard to do for lots of reasons. Our research is meant to reduce the uncertainty in the models used to describe the middle and upper atmospheres of the terrestrial planets." | Bucknell scholars envision a sustainable future.

Castle's NASA grant funded the purchase of a quantum cascade laser, a highly sensitive tool researchers will use to detect vibrationally excited CO2 as it collides with other molecules and atoms. The grant also provided supplies such as optics, research grade gases and liquid nitrogen used to cool the infrared detectors, as well as stipends for student researchers participating in the study.

Castle will pass on her findings to NASA scientists who will employ them in developing a more complete model of the Martian atmosphere. She will join other scientists funded through the Mars Fundamental Research Program studying facets of Mars as diverse as the formation of its polar ice caps, lightning in its skies and salt deposits at its surface.

"There's a lot of interest in Mars in general at the moment, from every angle," Castle said. "I'm very excited to learn more, and I'm sure we'll learn a lot in the course of completing the project."

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