Martian gullies formed by dry ice

www.nature.com...

The idea is that pressure variations and gas flows under the CO2 ice layer during defrosting season destabilize the regolith layer, causing a gas-lubricated debris flow. A thermo-physical numerical model was used to verify the claim.

It is certainly an interesting take on the martian gullies mystery, and would put recent liquid water flow claims into question.

a reply to: moebius

It is certainly an interesting take on the martian gullies mystery, and would put recent liquid water flow claims into question.

This will not be welcome news round these parts. Seriously, though, there are enough other hints at liquid water that the consensus is likely to remain that water was once more abundant, but more recently other factors have been causing weathering.

a reply to: DJW001

Indeed.

Mars HAD water. flowing, probably tepid, and it ate rocks.

why is this such a problem for people who "No water on mars" "Mars had water z!!!!!!!111" people?

in about 2.5 million years, it may have water again. it's got that funny tilt you know.

a reply to: moebius

It is certainly an interesting take on the martian gullies mystery, and would put recent liquid water flow claims into question.

In the near vacuum of Mars "atmosphere", liquids boil away.

However, ongoing gully formation has been detected under surface conditions much too cold for liquid water…

…has to be liquid volatiles flowing out and turning to gas.

Frozen subsurface gasses get rocked by impactors and or volcanic or geothermal activity at times, too. Causing huge flows and pooling of material before it evaporates or re freezes.

Imagine an impactor melting out rivers of methane and co2 that shape the terrain to look like water flow on earth. It eventually boils away leaving a "dry riverbed" channel.

a reply to: moebius

We conclude that martian gullies can result from geologic dry ice processes that have no terrestrial analogues and do not require liquid water

It's possible both processes are involved , evidence for briny water being involved in the flows comes from spectral signatures of perchlorates at the sites.

The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren't as extensive, they detected no hydrated salt.

Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.

Perchlorates have previously been seen on Mars. NASA's Phoenix lander and Curiosity rover both found them in the planet's soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.

MRO has been examining Mars since 2006 with its six science instruments.

"The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are," said Rich Zurek, MRO project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
www.nasa.gov...

a reply to: moebius

They make a good argument that explains the ongoing formation of the gullies. I snipped an image from the article that gives a good visual for their points:

These observations suggest that the CO2 condensation–sublimation cycle could play a role in gully formation. Here we use a thermo-physical numerical model of the martian regolith underlying a CO2 ice layer and atmosphere to show that the pores beneath the ice layer can be filled with CO2 ice and subjected to extreme pressure variations during the defrosting season. The subsequent gas fluxes can destabilize the regolith material and induce gas-lubricated debris flows with geomorphic characteristics similar to martian gullies.

Image and Text courtesy of Nature

It does make more sense than liquid water causing the gullies when temperatures are sub-zero. Obviously, dry-ice cycles don't preclude the presence of water elsewhere on Mars. For non-scientist me, I'll stand by and wait for the article to gain some media attention - it's only been out for 24 hours.

Images from the phoenix lander that scraped the surface and uncovered ice that subsequently evaporated.

image

Wet rover wheels, and ice turned up in tracks from rovers shows theres tundra like subsurface conditions, frozen gasses that when exposed vaporize, because of the near vacuum and the solar wind stripping away the atmosphere.

ice in rover tracks

originally posted by: moebius
It is certainly an interesting take on the martian gullies mystery, and would put recent liquid water flow claims into question.

I assume these gullies are in the polar regions, more specifically the North pole.

However, ongoing gully formation has been detected under surface conditions much too cold for liquid water

Nature.com
The polar regions are too cold for liquid water but the rest of the planet gets much warner.

Martian surface temperatures range widely from as little as 140 K (-133 C, -207 F) at the winter pole to almost 300 K (27 C, 80 F) on the day side during summer.

Source
Liquid water on Mars is still very likely as is evident by the fluvial formations and dark streaks imaged by MRO.

Add; Great find, moebius, by the way.

originally posted by: intrptr
In the near vacuum of Mars "atmosphere", liquids boil away.

I think we can consider Mars’ atmosphere far from a vacuum, or “near vacuum”. The atmosphere on Mars is 1% that of Earth however it does contain gasses and liquid water on the surface is evident by the images taken from the Mars Reconnaissance Orbiter.
NASA Confirms Evidence That Liquid Water Flows on Today's Mars

There have also been dust devils imaged, hard to image this in a near vacuum.

originally posted by: intrptr
Frozen subsurface gasses get rocked by impactors and or volcanic or geothermal activity at times, too. Causing huge flows and pooling of material before it evaporates or re freezes.

Where is the evidence of recent impacts or volcanic activity on Mars?

a reply to: Devino

Could be geothermal heat or residual from impactor long ago. Anywhay, there being evidence of erosion by "liquids" does not mean water flowed there.

Largest volcano in the solar system is on Mars, so we know there is volcanic activity.

I% of earth atmosphere is next to nothing, thats why I used the term "near vacuum". Thats why volatiles boil away when exposed or uncovered from under the surface layer. And then the solar wind strips it away, ongoing.

Mars doesn't have enough mass to have a molten core, thus generating a magnetic field from rotation to prevent solar radiation from stripping away the atmosphere.

Thats my understanding and why I think the 'evidence of water flowing' on Mars is scantily clad in a solicitation for funds to keep gong there too "search for life".

If the wealthy want to be first to return a lump of gold the size of a Volkswagen, then they should pay for the mission, not the taxpayer.

originally posted by: intrptr
Could be geothermal heat or residual from impactor long ago. Anywhay, there being evidence of erosion by "liquids" does not mean water flowed there.

It “could be” many things but the fact is that there is very good evidence of liquid water flowing on Mars. See link below to the NASA conference.
NASA Confirms Evidence That Liquid Water Flows on Today's Mars

Largest volcano in the solar system is on Mars, so we know there is volcanic activity.

We know there was volcanic activity on Mars. We don’t know how long ago this was and as far as I know there is no current activity today. If you know of any evidence to the contrary please link it.

The evidence of liquid water on Mars is current, not historic, as is the evidence of gullies formed by CO2 sublimation in the OP’s linked paper. This is evidence of recent or currently ongoing activity.

I% of earth atmosphere is next to nothing, thats why I used the term "near vacuum". Thats why volatiles boil away when exposed or uncovered from under the surface layer.

1% of Earth’s atmosphere is not next to nothing. It is very small in comparison yet substantial enough to not be considered anywhere near a vacuum. A near vacuum is void of matter such as in space. Space is not completely devoid of matter hence why it may be considered a “near vacuum”. Perhaps this is a debate in semantics.
Mars’ atmosphere is hardly void of matter as there are gasses present including water vapor and methane.
Volatiles also boil on Earth, they are by definition the tendency of a substance to vaporize.

Thats my understanding and why I think the 'evidence of water flowing' on Mars is scantily clad in a solicitation for funds to keep gong there too "search for life".

So you disregard all of the evidence and the expert opinions because you “think” it’s a conspiracy? Cool, I like it but I also disagree. I feel there is strong evidence for an ongoing conspiracy for over 30 years to not go to Mars.
ATS tread; National Geographic [THE SECRET STORY OF PLANET MARS]

If the wealthy want to be first to return a lump of gold the size of a Volkswagen, then they should pay for the mission, not the taxpayer.

Again I disagree, respectfully. There is a wealth of information that can be found on Mars and so much that we do not know. More of my opinion on this can be found in the above linked ATS thread.

a reply to: Devino

You're clutching at straws… hanging on slight differences in terminology I've used. As a laymen, I'm not scientifically accurate to be sure.

This is evidence of recent or currently ongoing activity.

I know, thats what this thread is about. Like the OP article stated and I quoted up top…

However, ongoing gully formation has been detected under surface conditions much too cold for liquid water…

That pretty much ices the cake.

originally posted by: intrptr
a reply to: Devino

You're clutching at straws… hanging on slight differences in terminology I've used. As a laymen, I'm not scientifically accurate to be sure.

Perhaps I am misunderstanding your point so just to be clear of what I mean I'll show the link one more time.

NASA Confirms Evidence That Liquid Water Flows on Today's Mars

I am not "clutching at straws" but linking scientific confirmation of evidence that proves liquid water is present on Mars today.

Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet.

By "hydrated minerals" they mean dissolved in H2O.
Here is more;
Recurring "Lineae" on Slopes at Horowitz Crater

These dark features on the slopes are called "recurring slope lineae" or RSL. Planetary scientists using observations with the Compact Reconnaissance Imaging Spectrometer on the same orbiter detected hydrated salts on these slopes at Horowitz Crater, corroborating the hypothesis that the streaks are formed by briny liquid water.

More images can be found here;
Braided Channels in Central Uplift of Unnamed Crater

Stay skeptical my friend but don't dismiss the evidence. At least open the links and read the articles.