It seems to me that the confirmation of liquid water mostly impacts landing site selection for future missions, in that the planetary protection protocols specifically prohibit any landings near liquid water with any lander at a sterilization level less stringent than that defined for the Viking landers (i.e., less than 30 spores per vehicle). Otherwise very attractive sites may end up on the verboten list if there are close-by RSL's.

Any idea if this might affect the landing site selection for the 2020 rover? Especially considering the fact that the 2020 rover will be caching samples for potential return -- if you land near RSL's, you have to postulate not only sterilizing the rover to the Viking standards, but also whatever follow-on vehicle collects the samples and returns them to Martian orbit...

-the other Doug

If we are so scared of contaminating Mars, why do we send anything there ?

If we really want to keep all the planets pristine, then we should leave them alone.

In fact, we should be more careful that we accidentally do not bring any "new" microbes back to earth !

I would suspect not. The two kinds of environments seem probably distinct, although I recall Spirit finding that "magic carpet" surface and wonder if it was actually on top of some briny liquid or slush.

The elephant in the room is that there are two distinct exploration pathways – Past Water vs. Current Water – and surface missions typical of ones we've seen that pursue one pathway aren't pursuing the other, so there needs to be some strategy. If only one of these pathways existed, we'd be pursuing it. Given that two pathways exist, do we "finish" one before starting the other, interleave them with separate mission architectures, or find a way to combine them?

One possibility for combining them would be to have a single craft for Mars-orbit-to-Earth sample return, and have sample returns from both kinds of environment travel from Mars surface up to that return craft. With craft weighing many tens of kg and samples weighing and 10 g, that would provide a lot of savings if we acknowledge that both kinds of sample return are desirable. Further savings would be achieved in sharing clean ground facilities on Earth for examining samples.

http://www.hou.usra.edu/meetings/lpsc2015/pdf/2327.pdf

Figure 1 in the above LPSC abstract shows some candidate RSLs in Gale Crater. These were mentioned during the press conference in conjunction with the possibility of a visit by Curiosity. During the question period one of the reporters raised the issue of planetary protection. The reply suggested that they could be observed from a distance at times different from the fixed MRO flyover time, which would be useful. The panelists also suggested that Mars 2020 could have a role and it was stated that the budget included some money for sterilization.

The PC recording can be seen here:

http://www.ustream.tv/recorded/74355422

It is worth listening to the Q&A on the topic of planetary protection.

The fact that these features are spread out over so many different regions of Mars separated by thousands of km seems to imply that its false positives that would be the main concern for a future mission, not somehow contaminating the entire planet with one mission. Though like others have said, since their occurrence is almost by definition on steep slopes that can't be easily reached in any case, it's likely to remain an academic question for a good while yet....

I think there are lots of ways to study/sample these areas if we want to. Of course, there are engineering challenges and a chance of failure, but it's not impossible.

A stationary lander could be paired with an aerobot with cameras on the lander and the aerobot helping the aerobot land precisely on an RSL, sample the soil there and bring it to the lander for analysis or even sample return. That would completely neutralize problems related to the steepness of the slope.

JRehling's post #47 proposing the water source makes good sense. In the main the popular press has reported the finding as salt water flowing on the surface of Mars giving the impression of a bubbling stream. The reality is that the RSL where hydrated perchlorates were identified are a flow in the geological sense of a land slip with ephemeral brine as the fluidizing agent.

'Fluidizing agent found on Mars' doesn't have quite the same ring to it in the headlines though....

This makes for rather interesting reading.

http://www.nature.com/articles/srep25106

Accumulating evidence of ocean and lakes, groundwater, streams and deltas, river valley networks seemingly traceable to precipitation, It is beginning to become clear that early Mars had an interesting hydrological cycle.

The question marks around the RSL's are growing again: http://www.jpl.nasa.gov/news/news.php?release=2016-215

Well Spirit at Tyrone demonstrated that a thin layer of regolith can provide for a relative humidity gradient protecting hydrated salts. If the regolith is breached then the atmosphere acts as a desiccant. This could explain the appearance and then disappearance of limited amounts of hydrated salts in RSL and would not contradict this latest measurement. Or is could be something else. I suspect it will be a long time before there is consensus on RSL.

A study published discussing inverted river channels in Arabia terra as a sign of a warm and wet climate on early Mars talks about ancient river channels flowing from topographic highs to lower regions from south to the lower northern regions. My question is where would meridiani planum fit along this topographic gradient? The rocks stu died by opportunity rover were mainly sulphate rocks suggestive of acidic water alteration . The inverted channels discussed seem to originate on early mars where water would be expected to form different rock types from those observed by opportunity! Maybe I am getting the ages wrong. Correct me if I am wrong.

The linked Planetary Society blog article provides an interesting read on the faint young sun paradox with respect to long lived surface water on early Mars and puts to bed some of the hypothetical explanations. However the article did miss the hypothesis that the solar system transiting through interstellar dust clouds could have the effect of significantly increasing the sun's output through the capture of molecular hydrogen. That hypothesis has always made a lot of sense to me.

http://www.planetary.org/blogs/guest-blogs...le-paradox.html

I saw two recent papers/references that seem relevant, or at least interesting.

FIRST, was a paper on the 11/22 year solar cycle and Jupiter (yes, related to the barycenter theory) which looked at
the 11.07 year cycle of solar atmospheric tides that results from Venus-Earth-Jupiter orbital resonances.

Solar Physics - May 2019, 294:60 | A Model of a Tidally Synchronized Solar Dynamo
https://link.springer.com/article/10.1007/s11207-019-1447-1

So, let's consider that Theory #1 the "solar cycle / planetary barycenter theory" might be correct
well,
let's consider that Theory #2 "Nice-Model" might be correct as well.

In that case, the early Sun had 4 gas giants between ~5 AU and ~17 AU.
Resonances would have driven massive solar dynamo effects.

Basically, if you have 4 gas giants on circular orbits within ~17 AU, you have tides stirring the Sun and stoking the fire.

SECOND is a combination of idea, the mention of lunar GRAIL data that the lunar surface is roughly 15% void space for the first few kilometers, and a review that the breccia and impact melt under Gale crater could be 17 km deep (for comparision, the Marianas Trench on earth is ~11 km deep) with an initial void space of 3,600 cubic kilometers.
This suggests that there is plenty of "space" for liquid water to exist in the Martian subsurface.
That implies that the real trick about water on the surface of Mars is keeping it from draining back down into the regolith.

Perhaps we only see Martian rivers when they run across compacted sediments or permafrost, otherwise, the water quickly soaks into the sand and gravel.

Flip the thinking to view rivers on the surface of Mars more like the meltwater channels on the top of a glacier, as soon as they encounter a lens of clean sand or a crack, they are gone.

https://phys.org/news/2018-01-glacial-mouli...ered-rapid.html

I don't know if this has been mentioned before, but the story is on several news outlets, so it seems appropriate to post the original paper here: Crocus melting on Mars:
https://iopscience.iop.org/article/10.3847/1538-4357/ab612f

Here is the complete abstract from the LPSC 2020 Marsbug.

https://www.hou.usra.edu/meetings/lpsc2020/pdf/1792.pdf

I believe the last sentence in the abstract is germane. There simply isn't sufficient precipitable water vapor in the atmospheric column to create meaningful brine.

I also thought this was quite interesting- but for a slightly different reason-

If a boulder can generate the necessary shadows from positive curved geometry,
wouldn't the negative geometry of a crater have a similar effect?

Also, a crater would seem to have an advantage of access to absorbed/adsorbed subsurface moisture.

You're right we don't hear much on this anymore. I recall that being part of initial speculation when the first gullies were discovered by MGS some 20 years ago. i got a sense that the cold-trap model didnt hold up but nevertheless i still like to armchair-speculate such processes may remain relevant at certain points in Mars' climate intervals to accelerate erosion in applicable places and contribute to such formations.

Just generally, from my physics background, layman's understanding of Martian weather and geology, and following forums and threads like this one, it has always seemed like there's no insurmountable barrier to small amount of transient liquid water forming on present day Mars, when the right conditions come together. But really solid evidence of it seems to be elusive, so perhaps, like me, people are waiting for something really direct and unarguable.

I'm sharing this LPSC abstract because it is quite interesting: a site that contains deltas, lake sediments, and a possible extinct underwater geyser basin

"A POSSIBLE SUBAQUEOUS HYDROTHERMAL SYSTEM IN MELAS CHASMA, MARS"
https://www.hou.usra.edu/meetings/lpsc2021/pdf/2432.pdf

My apologies for the thread necromancy, but it seems that this paper and any debate on it fits exactly:

Modern water at low latitudes on Mars: Potential evidence from dune surfaces

https://www.science.org/doi/10.1126/sciadv.add8868

Interesting summary
Snows or frosts possible as recently as 1.4 million years ago to 440,000 years ago.

This is in accord with modeled changes in the obliquity of Mars as below, resulting in cyclical sublimation and deposition of the ice caps. At higher obliquities the poles receive greater insolation and the CO2/water vapor content of the atmosphere increases. The increased greenhouse effect would cause a degree of warming with higher pressure and humidity resulting in deposition of water ice in the cooler, lower latitudes. I assume the 1.4 to 0.4 million year timescale for the features imaged by Zhurong is based on the last modeled obliquity sequence which indicates 7 or 8 cycles.

Not sure if this is the best topic for this post or if other members have posted this elsewhere already. Anyway, I noticed a SETI Institute Press Release of a presentation at the 54th LPSC concerning the identification of a newly discovered giant volcano on Mars located just south of the planet’s equator, in Eastern Noctis Labyrinthus and west of Valles Marineris. https://www.seti.org/press-release/giant-vo...discovered-mars. The authors’ abstract is here https://www.hou.usra.edu/meetings/lpsc2024/pdf/2745.pdf. I believe this is the same group that presented an abstract at the 53rd LPSC concerning a ‘relict glacier’ in this region. https://www.seti.org/press-release/remains-...t-low-latitudes

Water frost deposition in the Calderas of Martian Tharsis volcanoes esp Olympus Mons.

https://www.nature.com/articles/s41561-024-01457-7

P