High above the surface of Mars, winds circulate from dayside to night, and the air undulates as it passes over mountains and valleys far below, a new study shows.
These insights come courtesy of NASA’s MAVEN spacecraft, which now has provided the first detailed maps of winds in the Martian thermosphere, one of the highest layers of the planet’s atmosphere. The data, described in the Dec. 13 Science, could help researchers better understand how the Red Planet’s climate has changed over time by looking into how Mars’ atmosphere bleeds into space.
“Looking at how gas circulates in that layer allows us to better understand the rate at which the atmosphere is being lost and the way it’s being lost,” says study author Mehdi Benna, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Wind movement in Mars’ thermosphere is much simpler than on Earth, data from the orbiter show. A single circulating flow persists from season to season, continually moving air from the planet’s dayside to its nightside, whereas on Earth there are multiple flow patterns at any one time. “Oceans on Earth complicate the circulation patterns,” Benna says. “Mars doesn’t have all that.”
The spacecraft, which arrived at Mars in 2014, also recorded waves in the thermosphere generated by winds near the ground diverting around mountains and canyons (SN: 9/22/14). “When the spacecraft is flying over a mountain, we can see the wind shifting to accommodate the presence of that mountain 200 kilometers below,” Benna says. “MAVEN doesn’t carry [traditional] cameras … but we can see a picture of the topography in the winds.”
In all, the researchers tracked winds for one and a half Martian years. While it’s still too early to say precisely what this all means for the trickle of Mars’ atmosphere into space, Benna says that these maps lay the foundation for improved computer simulations that will help researchers figure it out.