Mars may still host liquid water flows in its warm seasons
In short: For decades, Mars was considered a frozen desert where water vanished billions of years ago. However, new data from NASA's Mars Reconnaissance Orbiter suggests the Red Planet might still host active, albeit briny, liquid flows today. These seasonal features offer a critical clue in the search for life.
NASA's Mars Reconnaissance Orbiter (MRO) has identified recurring slope lineae (RSL)—dark, finger-like features that appear on steep slopes in the southern hemisphere. These features exhibit a distinct seasonal cycle: they darken and appear to flow during the warm spring and summer months, only to fade during the colder winter. Observations confirm these patterns repeat annually, suggesting a dynamic surface process rather than a static geological formation. These recurring features are located specifically in the middle latitudes of the southern hemisphere. The MRO has tracked these seasonal changes across several distinct steep slopes. This data was first presented during a NASA news briefing in August 2011.
The mechanism behind these flows likely involves briny water. Hydrated salt traces were identified on these inclines via information gathered by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Much like salt on Earth's roads lowers the freezing point of water, these hydrated salts allow a liquid brine to exist even in the harsh Martian climate. Scientists believe this is a shallow subsurface flow where water wicks to the surface, creating the visible darkening. Johns Hopkins University Applied Physics Laboratory managed the construction and running of the CRISM tool. These flows typically appear when temperatures rise above minus 10 degrees Fahrenheit. The liquid is described by NASA as being briny.
This discovery challenges the long-held timeline of Martian hydrology. Although the general consensus held that surface moisture vanished around 3 billion years ago, MRO-based analysis revealed that liquid water deposited salt minerals between 2 billion and 2.5 billion years ago. This suggests water may have flowed for about a billion years longer than previously estimated, significantly expanding the window of time during which microbial life could have potentially survived on the planet. The research was published in AGU Advances on December 27, 2021. Scientists used crater counts to date the salt deposits, as fewer craters indicate younger terrain. The salts were mapped across clay-rich highlands and volcanic plains.
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Sources
- Summary by Intellect · source: NASA's MRO Sees Possible Martian Water Flows
- Also: NASA Confirms Evidence That Liquid Water Flows on Today’s Mars
- Also: NASA’s MRO Finds Water Flowed on Mars Longer Than Previously Thought - NASA
- Also: NASA Science — Mars Reconnaissance Orbiter - NASA Science
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