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Investigating a Distant World

Physics graduate student Shannon MacKenzie studies carbon deposits on Titan

By Tara Roberts

Shannon MacKenzieShannon MacKenzie’s research subject is far from her lab – in fact, it’s more than 1 billion kilometers away.

MacKenzie, a graduate student in the University of Idaho Department of Physics, studies Titan, Saturn’s largest moon and one of the most unusual objects in the solar system. She works in the lab of Jason Barnes, an associate professor of physics, and is part of a team of UI student and faculty researchers studying Titan.

Titan is larger than the planet Mercury and the Earth’s moon, has a thick atmosphere, and is the only place other than Earth that is known to have defined bodies of liquid on its surface.

“I come into work every day and get to look at these lakes and seas that are on the surface of another planet,” MacKenzie says. “It’s just a really interesting place with a lot of interesting questions left to answer.”

Unlike Earth’s watery seas, the liquid on Titan is made of methane and ethane. But MacKenzie looks at what the moon’s lakes leave behind when they evaporate – deposits of organic compounds known as evaporite, which are analogous to the salt flats around the Great Salt Lake.

MacKenzie identifies and maps potential evaporite deposits using data from the Cassini spacecraft’s Visual and Infrared Mapping Spectrometer. The deposits show up as bright spots on the moon’s surface.

Titan’s thick, hazy atmosphere makes precise chemical identification of Titan’s surface deposits difficult, though a recent break in the weather allowed Cassini to capture clear pictures of lakes and evaporite around the north pole.

MacKenzie is studying possible evaporite deposits in Titan’s equatorial region. The area is mostly a desert, but there are signs of two large evaporite basins.

“If this is indeed evaporite, at some point these basins in the desert region had enough liquid to form that evaporite,” MacKenzie explains.

This provides clues to how Titan’s atmosphere circulates. Researchers have speculated Titan’s weather cycles pole to pole, skipping the equator, which would explain the higher concentration of lakes at the poles.

“Our results indicate that something more complex is happening,” MacKenzie says. “Maybe instead of the liquid going from the north pole to the south pole, it’s going between the north and the equator.”

Since coming to UI in 2012, MacKenzie has enjoyed not only the chance to study Titan, but also the opportunity to collaborate with her adviser and labmates. She says Barnes is an enthusiastic researcher and teacher, and her fellow graduate students are always willing to discuss new ideas.

She also enjoys the opportunity studying planets and moons offers to work with scientists outside of physics, from geology to chemistry, as they seek to understand the solar system.

“In planetary science, I knew I’d get to attack problems in totally different ways.”