Dust Devils' Powerful Updrafts Could Drive Mars Climate

Mars’ atmosphere is often viewed as frigid and unchanging, but in studies of the red planet’s aeolian processes, nothing could be further from the truth — particularly where Martian dust devils are concerned.

Aeolian, or wind-blown, processes dominate the Martian landscape; from space, aeolian features such as vast dune fields have fascinated planetary scientists. But another dominant atmospheric phenomenon studied by robotic missions in Mars orbit and on the ground is the dust devil, which often leaves its mark as dark curved paths in the dust.

Scientists are now beginning to understand how these swirling dusty vortexes are able to beef-up to the size of tornadoes we find on Earth and how they could impact the Martian climate.

“To start a dust devil on Mars you need convection, a strong updraft,” said atmospheric science graduate Bryce Williams, of the University of Alabama in Huntsville (UAH), at the American Geophysical Union’s fall meeting in San Francisco last week.

Dust devils, on Earth, are minor meteorological curiosities when the landscape is heated by sunlight. As the surface warms the air above it, the heat rises through the cooler upper layers. This convection can start to form a swirling vortex a couple of hundred meters high during an otherwise windless day. But their Mars cousins can dwarf their terrestrial counterparts, often becoming long-lived features reaching up to 12 miles high.

Now, Williams and supervisor Udaysankar Nair have been able to show how these fascinating funnels of air and dust are able to become super-sized.

“We looked at the ratio between convection and surface turbulence to find the sweet spot where there is enough updraft to overcome the low level wind and turbulence,” said Williams. “And on Mars, where we think the process that creates a vortex is more easily disrupted by frictional dissipation — turbulence and wind at the surface — you need twice as much convective updraft as you do on Earth.”

This conclusion was reached after studying meteorological data from Australian dust devils and comparing that with observations by NASA’s Viking Lander mission. The researchers were able to create a 1-dimensional “planetary boundary layer model” that could identify the ideal conditions for dust devil formation in the Martian atmosphere and, as it turned out, for a dust devil to form on Mars, more powerful convection currents were needed at the surface layers.

This study is much more than just a curiosity about Martian dust devils, however. Considering the Martian atmosphere is, on average, less than one percent the pressure of Earth’s atmosphere (at sea level), dust has a significant impact on the planet’s climate. As dust devils provide a mechanism for kicking substantial quantities of dust into Mars’ atmosphere, they could act as a global climate control of sorts.

Read more at Discovery News