"We've thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand", said lead author Colin Dundas, a US Geological Survey scientist.
The researchers analysed narrow, down-slope trending surface features on Mars that are darker than their surroundings, called Recurring Slope Lineae, or RSL.
Based on the findings, researchers concluded that the markings weren't created by water, but by dry grains like sand and dust that accumulate and flow down the slopes.
The discovery of the seasonal flowing feature also known as "recurring slope lineae" or RSL in 2011 had evoked fascination and controversy and had been believed as a marker for liquid water flow or brine in a planet which was otherwise considered as dry. On board is the HiRISE camera, which has photographed the Martian surface in great detail.
Monday's news throws cold water on 2015 research that indicated these recurring slope lines were signs of water now on Mars. Liquid water would have readily extended to less steep slopes. It could be limited to traces of dissolved moisture from the atmosphere and thin films of water.
However, RSL remain puzzling.
The new report describes possible connections between these traits and how RSL form.
Darkening and fading might result from changes in hydration. "But there may be little liquid at the surface today", informed Dundas. According to the scientists, water is unlikely to be produced only near the tops of slopes at these angles and if it were, it should be able to flow onto lower slopes. That's bad news in the hunt for microbes, unfortunately.
SCIENTISTS have dashed hopes of Mars supporting alien life after realising the mysterious "water" marks were actually left by SAND. "Remote sensing at different times of day could provide important clues". The paper appeared in Nature Geoscience this week.
Operated by the University of Arizona, HiRISE was built by Ball Aerospace & Technologies Corp. of Boulder, Colorado. Lockheed Martin Space Systems of Denver built the orbiter and supports its operations.