There’s a saying from legendary comet hunter David Levy that Mark Moretto knows by heart: “Comets are like cats: They have tails and do precisely what they want.”
Moretto, 27, has been working to understand comets and their unpredictable behavior ever since he was in high school, when he began doing research with University of Maryland comet scientists Michael A’Hearn and Lori Feaga. At that time, the pair were team members on NASA’s Deep Impact mission, which flew by Comet 9P/Tempel 1 in 2005. Moretto analyzed Tempel 1’s outgassing jets — work that received the National Young Astronomer Award from the Astronomical League.
Today, Moretto is a graduate student at the University of Colorado in Boulder, where he continues to study active comets — now helping spacecraft to safely orbit them.
The challenge is that an active comet is constantly acting out, spewing tons of gas and dust into its temporary atmosphere, or coma. Inside it, a probe is buffeted by complex aerodynamic forces that are difficult to model. “There’s a lot of inherent ambiguity associated with the behavior of gas and dust in the coma,” says Moretto, which in turn creates “huge uncertainties.”
