One of the biggest astronomical finds of the past few years is in question as new evidence shows no signs of large amounts of water on Mars.
When NASA announced the discovery of larger amounts of liquid water on Mars in 2015, hopes were significantly raised that we could one day soon find evidence of life on Earth’s neighbour.
However, what was once a major scientific breakthrough may have been false hope, according to a new study published in Nature Geoscience by the US Geological Survey (USGS).
Working with the University of Arizona, Durham University and the Planetary Science Institute, the USGS research team has now identified these apparent signs of liquid as granular flows of sand and dust.
The team came to this conclusion by analysing the dark, narrow, down-slope-trending surface features – referred to as recurring slope lineae (RSL) – mostly found on steep, rocky slopes in dark regions of Mars.
Darker than their surrounding areas, RSL (for all intents and purposes) appear as liquid water, but looks can be deceiving.
Despite our understanding of how RSL form being limited, they were identified in this instance because they are identical to the slopes of sand dunes where movement is caused by dry granular flows.
Mars is very dry
Water can be ruled out because it would require the volume of liquid to correspond to the length of slope available, producing more liquid on longer slopes.
However, all of the 151 RSL examined in the study were found to end on similar slopes, despite very different lengths.
On top of that, if water were present, it would surely appear on the lower slopes, rather than just near the top.
“We’ve thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand,” said USGS scientist and lead author Colin Dundas.
“This new understanding of RSL supports other evidence that shows that Mars today is very dry.”
The research team hasn’t dashed all hopes of water being present however, as this discovery may be limited to traces of dissolved moisture from the atmosphere and thin films of water.