Personally ( and probably this is a bit weasel of me but even so..) I think conditions on mars have varied enough for both wet, damp, ever so slightly damp, and totally dry flows to have happened, although perhaps with a strong bias to the dry end of things. It just nags me that the issue keeps coming back up and being chewed over and none of us ever seem convinced enough by evidence one way or the other to reach a general consensus.

As important as the question of water on present day / geologically recent mars is, it sometimes feels like we're going around in circles with it.
Edit: Apologies, especially to Juramike, that was bad tempered of me.

The biggest organic chemistry lab in the solar system, with occasional outbreaks of heat and water via vulcanism and impacts..... For anyone interested in lifes origins it's got to be the place to look!

Thanks, I suppose it's the old more data needed scenario again.

Does anyone know the freezing points of perchlorate solutions? If they are within the range of temperatures at the phoenix site wouldn't we expect that perchlorate in the soil would form small quantities of liquid and wick downwards? If so that would point to an active source, which adds evidence to the 'oxidisers fall out of the martian sky' arguments.

I go away for one week to move house and everyone thinks they've discovered life on mars.. tut tut tut
Seriously, I'm going to wait for an official announcement before I let myself think anything.

Just so's you know, although I don't have the knowledge to contribute I follow this thread religiously, fascinating stuff!

I'd guess that the alkaline soil is one piece of evidence in favour of the superoxide idea, but there are a lot more to be found before it's proven- such as the superoxides themselves! Over simplified reporting, although i may be judging prematurely, having not read the thing..

Edit: now I've read it I think its less oversimplification, more two tentative interpretations on preliminary results, as always more data needed!

Looks like the ice is tougher than expected. Some great science has been done but I worry the second half of the mission might go a bit shakesperian....

I second that! Good luck, hope it's a great experience.

The tega results released so far are only preliminary, so small amounts of organics could still be revealed by more in depth analysis. If none are found then the mystery of where mars's organics went deepens. So far there haven't been any signs of peroxides or superoxides put forward as the leading theory of what got rid of them.

I would have said no (ground is warmer) because the atmosphere absorbs at lot less of the suns radiation than the ground does. I only skimmed through the paper but it looks to me like the temperature graphs are air temperatures at different hights above the ground, not direct readings of ground temperatures. I believe viking did measure ground temperature directly and found it ten to fifteen kelvin warmer than the air, but I can't find the results. Could someone with more knowledge confirm this or set me straight?

The impact in the thread next door would probably meet the requirements

Maybe I've missed something, but what happened to the preliminary results from the last two oven heatings of the sample that was already collected? The first two heatings, going up to 175 deg celcius I think, were reported briefly in a press conference, but I've heard nothing about the second two, going up to 1000 degrees. Did the other problems lead to them being cancelled?

Edit: also I was wondering if there will be a wet chemistry lab thread?

I agree that this doesn't prove the case for water, and that hydrated salts are a possibility, but I just don't see what you do on the animation: There are a lot of changes that could be due to different shadowing or image artefacts, but I don't see any consistent outlines between the two frames, and the shadowing around the lumps looks to change as well. Is there any chance you could draw me some outlines to make it a bit clearer?

Go on drop out of cyberspace, the view from here is just as interesting!

Edit; ICE, I meant doesn't prove the case for ICE, please oh great god of woo don't strike me down!

That's a helluva knack for thread finding you've got there! One of the threads mentions that the brightness temperature doesn't necessarily match directly with actual ground temperature, but if there's a close enough relationship between the two then water could have formed, and be stable over a narrow range of temperatures. The pressure seems high enough (barely but it is high enough). There's a lot of ifs to get past though, I'd only put it in the 'maybe' pile. If I had one.

That's an enticing thought Steve, but since we don't know if that even is ice yet (for sure), and we have no way of measuring ground temperature I think we're getting ahead of ourselves. Assuming it is ice I'd like to know why its formed a solid layer just beneath the surface, I'd read it was expected that ice deposited from vapour would simply fill the pores in the soil, implying processes involving liquid might displace the soil. How far down does the liquid formed by frost leaching travel before it hits temperatures cold enough to freeze it? I'm wondering if the solid layer could be the result of hundreds of thousands of years of tiny amounts of brine from frost leaching sinking into the soil? If it is cold and protected enough there it might have been there for a looong time.

I think the ground is usually about 15 degrees warmer than the air temperature, which would mean the ground is at -15 deg celcius, at a very rough guess. That's still to cold for pure water to melt, so unless the experiments show something in the ice which lowers the melting point either: its not melting it just looks a bit like it is, or that's not water ice, or the apparent darkening is some kind of camera artefact, or something else I haven't thought of...

I was wondering when someone would say that! What I was getting at was whether or not Nick was suggesting the ice formed in a way that normally occurs at much lower temperatures, and if he is, why he thinks this would be the case? Crystal formation, is something I'm studying as part of my PhD so I was wondering if nick had some piece of knowledge on how the martian conditions affected the ice forming process.
EDIT: I changed some things for clarity.

Nick I don't fault your logic, but can we make water crystals from vapour with no liquid stage, in simulated mars conditions, here on earth? I was under the impression that as a crystal forms from vapour below 273 kelvin but above roughly 180 kelvin there is a nanometers thick liquid layer over its surface kept liquid not by impurities but by pressure from van der waals forces. I hope you don't take this as a nitpick, I'm just trying to be sure of what you mean.

It easily decomposes into oxygen and water if I remember, although ... here's a wild speculation to pass the time: H2O2 from the atmosphere (theorized to form during dust storms) is mixed with the soil, and then partly decomposes into a highly concentrated H2O-H2O2 mix with a freezing point low enough to stay stable in martian arctic conditions, producing dampness and making the soil stck together ... ...Nah I can't make an argument for that, I don't know what conditions it needs to decompose. (coughs and looks a little embarresed)
Presumably TEGA could guess at which it was by looking at the ratio of oxygen to hydrogen released?

EDIT: Actually to quote wikipidea: so I'll put an 'I told you so' in my pocket just in case

Ferric sulphate has also been suggested here, and since iron and sulphate compounds are more common than chlorides on the surface are probably more likely culprits, if it is dampness. As Doug has pointed out in the past, there are any number of things you can mix with water to lower its freezing point. Also I remember that very thin films of water adhered to grains can come under enough pressure from van deer waals forces (If I've spelt that right) to lower the freezing point to 180 kelvin. Also there are a lot of other possible causes of stickiness. We'll know better when TEGA spits out some results.
I feel like a small child in a car shouting 'are we nearly there yet' at his long suffering parents...

Thanks for the info tty, I was under the impression it was still being debated.

Congratulations on coming through what sounds like a very rough patch Nick, and congratulations on getting married!
Vulcanism on mars would have been a lot more active at the end of the late heavy bombardment, would that not have kept at least some locales warm between, and for some time after, the giant impacts? I'm not sure when the giant basins were formed. Could a more or less continous stream of smaller impacts contribute to keeping the planet warm? I'm afraid I'm throwing ideas around wildly here as I'm not familiar with how the late heavy bombardment/final planetary accretion was structured in time.

My uneducated guess: To produce heating over a long time or large scale an impact would need to trigger vulcanism on a global scale. So I'd think the chixelub impact, where a ten KM body hit mexico leaving a crater 200 odd km across, and maybe triggered vulcanism in the deccan traps on the other side of the earth, as a reasonable hand waving lower limit. As to how long it would last, I'd guess hundred to tens of thousands of years, but not hundred of thousands or millions unless the impact was really huge (just a stab in the dark). I doubt vapourized rock could comprize an atmosphere that would be cool enough for water, so vaporised ices and volcanic gases are the likely candidates. As the vulcanism or residual heat from a really big impact dies down i imagine the surface becomes cooler, gases making up the temporary atmosphere freeze out and atmospheric pressure drops back toward 0.01 bar. And Nick it's good to see you posting here again.