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TheAnt
Cartography work carried out by USGS have revealed further proof of ancient lake beds and signs of Mars-quakes in the Valles marineris region.

A shorter pressrelease from JPL.
TheAnt
Warming by asteroid impacts might yield a too transient warming to explain the erosion seen on Mars, now Penn state university suggest that dramatic climate cycles created somewhat warmer longer periods that could explain how running water carved Mars' surface.
TheAnt
CNRS, Laboratoire de Planétologie et Géodynamique de Nantes, France: Moraines left by carbon dioxide glaciers on Mars.
atomoid
QUOTE (TheAnt @ Dec 2 2016, 12:14 AM) *
Warming by asteroid impacts might yield a too transient warming to explain the erosion seen on Mars, now Penn state university suggest that dramatic climate cycles created somewhat warmer longer periods that could explain how running water carved Mars' surface.

interesting.. reinvigorates the uncertainty around assumptions raised by the Feb 6th 'NASA's Curiosity Rover Sharpens Paradox of Ancient Mars' which seems to suggest ruling out past acidity as a candidate for possible carbonate sequestration, at least in the Gale deposits.
serpens
It seems that analysis of ancient rocks on both Earth and Mars has provided no evidence of greenhouse gasses as an explanation for warm wet environments under a faint young sun. When empirical evidence clashes with modelling it is prudent to re-evaluate the assumptions underpinning the model. One hypothesis that I find of interest is the possible effects of the solar system passing through interstellar dust clouds. There would be minimal attenuation of solar flux but the capture of molecular hydrogen would result in a significant increase in the sun's luminosity. McCrea, W.H. (1975). Ice Ages and the Galaxy, Nature 255, 607–609 suggests that an encounter with interstellar cloud densities of 10^5 to 10^7 H2/cm3 would increase the Sun’s luminosity by up to 100 percent during the course of an encounter.
TheAnt
Boiling water might explain many landforms on Mars.
Yes boiling, due to the very low air pressure, if the temperature get high enough to melt any ice the liquid water will instantly start to boil.
serpens
More likely any exposed ice would sublimate , Phoenix trench "Dodo-Goldilocks" for example.
JRehling
Relatively small changes in conditions can lead to important changes in dynamics. An ancient Mars with slightly higher surface pressure would enable a liquid phase of matter.

However, it's not only different climates that allow this. Mars has higher subsurface pressure now than its surface pressure now. Water ice with a bit of regolith on top of it can reach conditions that allow a liquid phase. Boiling of that water would create rapid expansion that would move that regolith while relieving the pressure that enabled the liquid phase in the first place. Slightly different climates could allow profoundly different dynamics. There are a lot of variables to contend with.
Jaro_in_Montreal
An item of interest, from June 2017.....

http://www.lanl.gov/discover/news-release-...tified-lake.php

QUOTE
Rover findings indicate stratified lake on ancient Mars
A long-lasting lake on ancient Mars provided stable environmental conditions that differed significantly from one part of the lake to another.
imipak
"Researchers have found evidence of an existing body of liquid water on Mars. What they believe to be a lake sits beneath the Red Planet's south polar ice cap, and is about 20km across."

https://www.bbc.co.uk/news/science-environment-44952710
Steve5304
QUOTE (imipak @ Jul 25 2018, 04:09 PM) *
"Researchers have found evidence of an existing body of liquid water on Mars. What they believe to be a lake sits beneath the Red Planet's south polar ice cap, and is about 20km across."

https://www.bbc.co.uk/news/science-environment-44952710



Cant wait for the update!! In 2057!! mars.gif :Sarcasm:

Seriously a spectacular find if true, would be game changing an only a mile below! Safe from most of the radiation.


Such a tease. We should stop everything we are doing to figure something out to check it out. Re-purpose the 2020 rover, build a cryobot.

serpens
Pressure melting at the basal layer of the poles has been anticipated but apparently this liquid brine is only a metre deep which means that detection was an extraordinary analytical effort.
Explorer1
The Nature article says at least 1 metre deep (i.e. a minimum).
Though 1.5 km down, and at the South Pole... nothing's getting through that any time soon!
ectoterrestrial
biggrin.gif

Neat but ambiguous. The claim of finding a liquid at the coldest and most insulated place on Mars deserves some healthy skepticism.

All radar can tell us is about changes in index of refraction for that frequency.

On Mars, this gets more interesting as the undigested iron on the surface of the planet contributes to the index of refraction.

This reflection could be the interface between clean ice and dirty ice (or icy dirt).

A 1 meter thickness is an inference from the physics. The vertical resolution is much lower.
ngunn
QUOTE (ectoterrestrial @ Jul 28 2018, 06:47 AM) *
The claim of finding a liquid at the coldest and most insulated place on Mars deserves some healthy skepticism.


Skepticism is always good. However, if there is any significant body of liquid water still present on Mars in this era of scanty atmosphere, then under pressure at the bottom of an icecap is exactly where I'd expect it to be.
marsbug
QUOTE (ectoterrestrial @ Jul 28 2018, 06:47 AM) *
biggrin.gif

Neat but ambiguous. The claim of finding a liquid at the coldest and most insulated place on Mars deserves some healthy skepticism.

All radar can tell us is about changes in index of refraction for that frequency.

On Mars, this gets more interesting as the undigested iron on the surface of the planet contributes to the index of refraction.

This reflection could be the interface between clean ice and dirty ice (or icy dirt).

A 1 meter thickness is an inference from the physics. The vertical resolution is much lower.


True, but in fairness the investigators do mention that and other possible intepretations in the original work, and state only that, given the currently available evidence, a liquid water layer is their favoured explanation - they don't claim this is 'case proved', merely 'evidence in support of'. There's no question that this needs a lot more exploration, and the putative 'lake' is just one (provocative!) explanation at this point. Non-expert journalism, and a need to get clicks on headlines so money is made. wages are paid, and food is bought, has a lot to answer for. That said, even Emily Lakdewalla on the Planetary Society (who is usually quite groundingly skeptical) seems guardedly optimistic that this might really be liquid martian H2O. I think part of the reason is that basal melt on Mars has been predicted for a while.
atomoid
interesting read Paleolakes of Northeast Hellas
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