While the name dust devils may seem rather harmless, new photos from NASA's Opportunity rover show that the massive dusty spin-ups that stake a claim to Mars’ barren surface can grow to be the size of tornadoes, much larger than the average dust devils that form in different parts of the Earth.
Earthly dust devils tend to top off at about 30 feet in width and have an average height of about 650 feet. The ones measured on Mars, however, can reach more than 330 feet wide and stretch up to 12 miles above the surface, according to NASA.
"This is one of the best dust devils that we have seen,"Ray Arvidson, the Opportunity's deputy principal investigator, told Mashable. “We are lucky to have captured this one in an image!”
Just like they do on Earth, dust devils are normally seen on clear days when the ground is being heated by the sun. The warm air just above the surface then rises quickly through a pocket of cool air, which can kickstart the rotation if the conditions are suitable.
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One of Mars' massive dust devils seen from NASA's Mars Exploration Rover, the Opportunity.
(NASA)
Using photos taken by the Mars Reconnaissance Orbiter in 2012, scientists learned that dust devils on Mars required a more powerful updraft to form a vortex like those seen on Earth.
"To start a dust devil on Mars you need convection, a strong updraft," Bryce Williams, a University of Alabama in Huntsville atmospheric science graduate student, said in a press release. "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. 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."
Now the concern about the dust devils is what type of lasting effect the rising dust has on the planet’s atmosphere and climate.
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"The Martian air is so thin, dust has a greater effect on energy transfers in the atmosphere and on the surface than it does in Earth's thick atmosphere," said Dr. Udaysankar Nair.
Dust in the planet’s air cools the surface during the day and gives off long-wave radiation that heats the surface at night.
Although catching traces of former dust devils that have blasted across the surface is a common occurrence, capturing a photo of one in progress has proven to be a difficult task.
However, despite the twister’s ravaging speeds, the Opportunity rover has benefitted from the dust devils by allowing it to clean off material stuck to the solar powered robot.
The Opportunity rover originally landed on Mars in January 2004 and was intended to last only 90 days. The robot has now logged 27 miles since its arrival, according to Spaceflight Now.
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As part of its investigation of 'Victoria Crater,' Opportunity examined a promontory called 'Cape Verde' from the vantage point of 'Cape St. Mary,' the next promontory clockwise around the crater's deeply scalloped rim. (NASA/JPL-Caltech/Cornell)