Preliminary results from the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite are in, and a George Mason University physicist is doing his part to piece together the story they tell.
MAVEN, designed by NASA and individual scientists from around the world, was sent to Mars in 2013 to explore the Red Planet’s ionosphere, interactions with the sun and solar wind, and upper atmosphere. Erdal Yiğit, a faculty member in George Mason’s Department of Physics and Astronomy, was selected to be a co-participating scientist for the project.
Yiğit and Scott England, his colleague at the University of California, Berkeley, set out to prove that gravity waves produced in the Martian lower atmosphere, close to the surface of the planet, can reach such high altitudes (up to 150-200 km) that they can contribute to disturbances in the upper atmosphere.
Now that he’s received the data from MAVEN, which measures the fluctuations of carbon dioxide molecules in the atmosphere, Yiğit has been able to compare his computational modeling results with MAVEN’s wave signatures to see how closely they matched. His model simulations were based on a state-of-the-art gravity wave code that estimates the effects of these waves in planetary atmospheres. Yiğit developed the wave code in 2008 in collaboration with Alexander S. Medvedev at the Max Planck Institute for Solar System Research in Göttingen, Germany.
The simulations “were in good agreement with the observations,” Yiğit said. “However, the enormous fluctuations are much larger than what is seen in the model. So this could mean that some other mechanism is playing into these fluctuations as well. There must be something additional that we have not yet discovered, or maybe we are not yet fully capturing the intensity of gravity waves on Mars.”
Finding the answer is important, he said, because improved understanding and prediction of how gravity waves influence the upper atmosphere is crucial for planetary missions.
“If you want to land on the surface of Mars, you have to pass through the upper atmosphere,” Yiğit explained. “We need to know what kinds of disturbances are in the upper layers so that any technological mission is prepared for them. If you have a spacecraft taking measurements and trying to land, these waves can disturb the instruments. So there are all kinds of implications for why we should understand them, beyond fundamental science.”
At a press conference in November, NASA announced that the first returns of MAVEN data confirmed the planet once had an ocean and air, but it became a frozen desert when the sun’s solar wind swept away its atmosphere.
“That’s the big effect,” Yiğit explained. “Because the atmosphere is thin and there’s not a significant shielding environment around the planet. I believe that the effect of the lower atmosphere can modulate this effect.”
Yiğit’s research also delves into atmospheric escape—the loss of planetary atmospheric gases to outer space. “Without understanding dynamical information, or how things move around, we cannot really understand the chemistry of Mars’ atmosphere,” he said. The individual molecules behave differently at different altitudes, he added, which will require extensive modeling.
Yiğit’s portion of research for MAVEN is scheduled to end at the close of this academic year. Until then, he is working with a master’s student, applied and engineering physics major John Lear.