A team at UC Berkley has analyzed data from the now-retired InSight lander and found evidence for an abundance of water deep in Mars’ crust. Do not expect to see astronauts digging wells on Mars anytime soon though: they would need to drill about three miles down to get to the water, which is likely found trapped within rocks and between rock layers.  See the report in the Proceedings of the National Academy of Sciences here. 

Scientists have found abundant evidence for water in the ancient past of Mars, in the first 1–2 billion years of its history. The open question for many Mars scientists, including many within Astrogeology, is “Where did the water go?” Water is necessary for life, so NASA considers finding evidence of past or present water on Mars a top priority. 

Someday, humans (aliens we become) when physically visiting Mars will need water to sustain us and a lot of equipment, but it is burdensome to transport ~140 million miles away. With no near-by gas stations, but with enough water found, explorers could split the water into hydrogen and oxygen to make necessary fuel to power the equipment. 

But where else have scientists looked for water on Mars?

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Mid-Latitudes of Mars: 

USGS Dr. Colin Dundas studies widespread, subsurface ice located in the mid-latitudes of Mars, sometimes found >100 meters thick starting within a meter of the surface. The ice plays hide-and-seek because usually it is hidden by a layer of dust (typical for Mars’ blinding dust storms) or regolith, until a fresh impact crater, or erosional scarps develop and expose it. Step into the realm of discovery with Dr. Colin Dundas’ research in A large new crater exposes the limits of water ice on Mars and Exposed subsurface ice sheets in the Martian mid-latitudes.

Martian Slopes: 

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Scientists have taken a look at streaks named recurring slope lineae (RSL) on Martian slopes, which ebb and flow with the seasons as other evidence of water on Mars. USGS Dr. Colin Dundas has contributed significantly to the understanding of these features recorded in articles like An aeolian grainflow model for Martian Recurring Slope Lineae. His findings posit that these features are the result of dry granular flows, similar to the movement of sand dunes, and do not necessarily indicate the presence of liquid water. You can also explore Granular flows at Recurring Slope Lineae,  and Flowing Sand, Not Water, Source of Recurring Dark Martian Streaks, as both articles support the idea that the RSL that we see are very dry.

Martian Poles: 

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USGS Dr. Timothy Titus’ research has answered questions about the composition of the white stuff atop the Martian poles that resemble Earth’s polar caps.  When asked about the article Exposed Water Ice Discovered near the South Pole of Mars | Science, lead author Dr. Titus states the following: 

My research was one of the many pieces of the puzzle that shifted our perspective of Mars’ South Polar Residual Cap from a cap almost entirely composed of CO2 ice, to a cap that is mostly composed of H2O ice, with a thin veneer of CO2 ice covering it. In other words, the CO2 ice is the icing on the H2O-ice cake.

In the book, The Martian Surface, Chapter 25 titled Martian polar processes, Dr. Titus and others reviewed research about the polar regions, which contains the majority of known H2O-ice deposits, distributed between the residual caps and near-surface ice in the regolith.

We have to look to Mars’ past for liquid water at the surface. . . 

Scientists target places on Mars to find water that resemble ancient riverbeds and lakebeds, like these below. 

Gusev crater: NASA sent the Spirit rover (RIP, March 22, 2010) to Gusev, the Mars Exploration Rover (MER) landing site, to explore the possibility that it had a watery past. But Spirit found little evidence that Gusev was an ancient lakebed as previously thought. No lakebed sediments were found, but many of the rocks had coatings and other characteristics that may be evidence for minor aqueous alteration. Spirit also found abundant silica at Gusev, which likely formed in hot springs similar to those found on Earth. 

Gale crater:  Spying from orbit on Gale (a large impact crater with a massive, large mountain in the middle), NASA’s Mars Reconnaissance Orbiter saw different minerals that occur in layered rocks, which often indicate the presence of water. In 2012, NASA targeted Gale as a landing site, sending their Mars Science Laboratory rover, Curiosity,  to investigate the terrain. Curiosity found hydrated salts, stratified rocks, clay-bearing rocks, and an alluvial fan, all indicative of Gale having a watery past.

Meriandi Planum: The Opportunity rover (RIP, June 12, 2018) sent by the MER mission found gray-blue concretions that were strewn across the landing site. Scientists have said those tiny spherules, nick-named “blueberries”, are non-edible and made up of hematite, which typically forms in association with liquid water. Martian concretions have provided clues about the past presence of water on Mars. This photo of the blueberries was captured by the Microscopic Imager and colorized with Pancam imagery at USGS. Dr. Herkenhoff was the science lead for the Microscopic Imagers on the Mars Exploration Rovers (MER) Spirit and Opportunity rovers. 

Jezero crater: In many Slavic languages, Jezero means lake. The Mars 2020 Perseverance rover is exploring this ancient lakebed, having found that Jezero crater’s floor is made up of volcanic rocks that have interacted with water. Jezero crater is thought to have once been a vibrant lake, possibly teeming with life, some 3.7 billion years ago. 

USGS Dr. Ryan Anderson, Mars 2020 mission team member, said the Perseverance rover is continuing to search for clues of Mars’ watery past. 

On July 18, Perseverance laid eyes on an interesting rock nicknamed “Cheyava Falls”, described as vein-filled, with leopard-like spots that may have been formed by ancient life. The rock is said to contain olivine and sulfate, and thought to be a remnant of water that once flowed on Mars. Cheyava could also provide insights to Mars’ potential for both past and present life, so the team members plan to send this sample back to Earth for further studies. The information and rock are a must see, here.