At a Glance

What appeared to be water flowing on Mars' surface is actually an optical illusion, according to a recent study.The flows are the result of sand avalanches and shadows cast by sunlight.

Seasonally recurring streaks on Mars had researchers considering the presence of water on the Red Planet, but a team of researchers proposed a theory that these flows have nothing to do with water at all.

According to a recent study, the scientists believe that that create an optical illusion.

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, reports Phys.org. Researchers determinedthey occurred during the hottest times of the planet's year and change in away that resembles flowing water.The lines are dark flowsknown as recurring slope lineaeand are seen on the warmest slopes of the planet's equator, according to the study.

In the study, the scientists proposed various sources of liquid water that could be causing the phenomenon. Possible sources included aquifers under the surface or melting ice dams.

Some researchers say the water theory is unlikely because, if there were ice on Mars, it would be more likely to pass from a solid state into a vapor rather than meltingand evaporating, according to Phys.org.

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The images above show the formation of the recurring slope linae on Mars' surface.

(Nature Geoscience/Image MRO, HiRISE, NASA/JPL/University of Arizona)

Instead, the researchers believe the flows are due to shifting sands.

According to the study, heat generated on Mars during the hottest periods causes the top layer of dirt and sand on the surface to heat up, while the particles underneath stay cool. This temperature difference triggers the pressure in small pockets of gas trapped between sand particles to change. They begin to move upward, which pushes the sand particles and causes them to slightly slip downhill, similar to small avalanches.

“We suggest that this dry avalanche process can explain the formation of the recurring slope lineae on Mars without requiring liquid water or CO2 frost activity,” wrote the researchers.

The difference in color comes from the newly fallen particles as they move underneath shadows from boulders or outcrops, typically during the afternoon, when the sunlight has a more defined angle, reports Phys.org.

“If confirmed, the absence of surface liquid would significantly modify our understanding of the Martian environment, and its current habitability should be reassessed,” the researchers wrote. “Future experimental studies will be conducted to better quantify this process.”

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