The answer may lie in features called Recurring Slope Lineae (RSL) because of their shape, annual reappearance and occurrence generally on steep slopes such as crater walls.
RSL, dark flow like features, emanate from bedrock exposures at Palikir crater on Mars during southern summer.
These flows are observed to form and grow during warm seasons and fade or completely disappear in cold season.
Now, Lujendra Ojha of Georgia Institute of Technology and Georgia Tech assistant professor James Wray looked at 13 confirmed RSL sites using Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) images.
They did find distinct and consistent spectral signatures of ferric and ferrous minerals at most of the sites.
The minerals were more abundant or featured distinct grain sizes in RSL-related materials as compared to non-RSL slopes.
"We still don't have a smoking gun for existence of water in RSL, although we're not sure how this process would take place without water," said Ojha.
"Just like the RSL themselves, the strength of the spectral signatures varies according to the seasons. The signatures are stronger when it's warmer and less significant when it's colder," he explained.
"NASA likes to 'follow the water' in exploring the red planet, so we would like to know in advance when and where it would appear," added Wray.
"RSL have rekindled our hope of accessing modern water, but forecasting wet conditions remains a challenge," he said.
The findings indicate that predicting where RSL would appear is, at best, a guessing game, said the study published in the journal Geophysical Research Letters.