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Arthur T Knackerbracket has found the following story:
The revelations come via some plucky Mars geologists and the European Space Agency's Mars Express Orbiter. The spacecraft, launched in 2003, constantly circles the planet and is fitted with a number of high resolution cameras constantly snapping images of the Martian surface. Researchers at the University of Utrecht, led by Francesco Salese, pored over these images, intently studying 24 deep craters in Mars northern hemisphere looking for signs that water once flowed there.
Their findings, published in the Journal of Geophysical Research: Planets[0], show that almost all of these craters give signs that they once contained flowing water. That led the researchers to believe that Mars once had a reserve of water locked between 4,000 and 5,000 metres below Mars' sea level.
[...] The craters show a wide variety of features: Channels carved by water into their walls, evidence of sapping valleys formed by erosion and the presence of shorelines and terraces created by standing water. There was also evidence of deltas -- which are formed by slow moving water dropping sediment -- in 15 of the 24 craters. The researchers did not find evidence the water had flowed in from outside the craters, leading them to believe that they were fed from the ground up.
Because every crater showed geological remnants of water activity between approx. 4,000 and 4,800 metres, the team suggests the idea that all of the craters they studied may have been connected by the same underground water system -- though they can't be sure based on this evidence alone.
[0PDF seems to be stored in a jar of molasses]
(Score: 2) by Hyperturtle on Saturday March 02 2019, @02:12PM
It could be essentially glacier water, melted via the impact that formed the actual crater.
The water may still be there, frozen solid like a brick, and only flowing when heated up.
I'm not knowledgable enough about how long insulated ice of varying thickness on another planet with differing "sea levels" and gravity in a tenuous wispy atmosphere would be able to keep the water melted and flowing--but I imagine that after a gusher, it'd essentially scab over as surface ice formed to staunch the flow, and the regular weather on Mars would serve to blow dust in over the years and cover up everything that most obviously points to water (like reflections and exposed ice or even wet spots).
I have hope (or I expect anyway) that there is plenty of water ice under the soil in the form of glaciers (for lack of a better term). How much and how accessible that all is, I couldn't guess. But I can imagine that any future colony need only dig to find it, and I even expect that any industrious initiatives to dig down to build an underground community may be hindered by an unexpected layer of ice. It might not be an aquifer like here on Earth, but it could be icy soil that gets in the way and starts to melt when exposed to the heat generated by human habitation in the nearby vaults--sort of like permafrost melting when exposed to heat.
I expect some types of construction to be rendered unstable due to industrial activity causing long frozen ground to warm up and lose the water (such as via causing it to contribute to localized humidty in any spaces created underground) and introducing the risk of collapsing or underground land slides due to shifting soils. We already can see the ground sinking on Earth where water (or oil) has been pumped out of the ground; subsidence causing building damage is not a new issue and I expect it will present itself on Mars as well without proper safeguards.
Or, the water is all gone and it's bone dry and there's nothing to be excited about. (I wish K'Breel and the Council of Elders could set forth an official pronouncement regarding this news; I haven't heard about any gelsac piercing in a long time...https://www.alternatewars.com/SpaceRace/Red_Planet_Dispatches.htm/ [alternatewars.com])