"Scientists Discover Giant Reservoir Of ‘Hidden Water’ Just Three Feet Below Mars’ Grand Canyon"

and:

"The water in Valles Marineris may be mineralized, but the scientists believe it is more likely to be in the form of ice. This raises the issue of how the water ice is retained in a region of Mars where it would normally evaporate. "This suggests that some special, as-yet-unclear mix of conditions must be present in Valles Marineris to preserve the water — or that it is somehow being replenished," ESA said." https://blog.physics-astronomy.com/2...ervoir-of.html

that sounds good

i just hope its not contaminated with something (chemical/biological) substance.

Tastes like well water if you ask me.

I idly wonder if water actually would "evaporate," if there is no atmosphere out there for the water to "evaporate into."

And – "where the hell did Mars's atmosphere go?" I don't remember about Mercury, but "planets" usually have a very thick one, of some composition or another.

Sundial, I'm old and quite retired now, but I used to teach astronomy and physics. There's lots (and lots and lots...) of misconceptions in your one sentence. Let me explain:
The atmosphere provides pressure to keep the molecules liquid. Reduce the gas pressure and you reduce the temperate at which the liquid will change to gas. Raise the pressure, you raise the temp. at which it changes. Water changes to gas at 212 deg. F when the pressure is what the earth's atmosphere provides - commonly referred to as "1 atmosphere pressure", btw.

As for Mars' atmosphere, that planet is significantly smaller and has about 1/3 the gravity of the earth. It still has an atmosphere, but much less than the earth has (about 0.01 the density and pressure: see https://mars.nasa.gov/all-about-mars/facts/ ). So any liquid water there evaporates at a much lower temp. than on earth.

Once it does that, however, Mars doesn't have the gravity to hang on to that evaporated water forever, so eventually those molecules float off into space.

Now the water underground (on Mars, I mean) is a much different story.

Thank you for the "physics explanation." Nevertheless, it has always struck me as a bit odd that this planet among all the others has virtually no atmosphere. Was this always the case? (Obviously, "poor Mercury can be excused ...") This planet is located beyond our own, farther from the Sun, yet it seems to have no dense gaseous envelope. In fact, "it is entirely noticeable by its absence." What happened here?

Hi sundialsvcs. Allow me to expand on atmospheric considerations a little. Most of the planets are Gas Giants, sort of ALL atmosphere but Jupiter is so massive with so much garvity that it is a possibility that the core is so compressed and cold that it became metallic hydrogen, as hard as that is to imagine. There are rocky moons, some even slightly larger than the planet Mars, but let's focus on the planets for now even though there are similarities with some moons just because of sheer mass.

There are only four rocky planets, the four innermost. Mercury is so small, so gravitationally bound and so hot (on one side anyway) from the extreme proximity to our Sun, that for any practical purpose it essentially has no atmosphere that has ever been detected. Venus has a thick atmosphere but not by dimension, just by viscosity. It's sort of "soupy" and really nasty. Most people think of the Earth as having a vast atmosphere but that's only in surface area not in depth or volume, well... except relative to common human dimensions. If we could view the Earth as the size of the common schoolroom globe, you know, maybe 18-22 inches in diameter, the atmosphere would be no thicker than the thickness of a dime. No atmosphere on rocky worlds to date has been found that is thick in dimensions, just some in density.

What's with the "if"?

But if anyone wants ice "out of this world", there's no need to go further than the Moon...

So far, there seems to be water most everywhere.


My all-time favorite cosmic find is of course sugar!