You are not logged in.
Vincent:
There is no good way to dry carpet except streams of heated dry air. Even then, the pad underneath (which most homes and apartments generally have) will mildew before you can get it to dry. If you have carpet over pad, I'd strongly recommend pulling them up and drying them. It is possible to reuse them, but there may be staining or shrinkage distortion.
A lot depends upon how deep the water got, in order to wet your carpet. It will infiltrate the walls and wet your sheetrock, your insulation, and your framing. If the sheetrock shows no signs of disintegration above the baseboards, you do not have to remove it. Mold will develop in the wet materials inside the wall, but then will die once the water is dried up.
You generally do not need to rip out walls barely wetted somewhere hidden down inside the baseboards. I know the remediation guys say you need to rip it all out, but that's how they make more money. Mold does not live in the dry.
GW
The Saturn-V boosters that might have supported these "Apollo 19 and 20" missions are pretty well accounted for at other sites on the internet. Most of the components (stages) have been on public display since the 1970's Apollo-Soyuz mission (supposedly "Apollo 18"). You still cannot launch to the moon without an adequate rocket today, and you certainly could not, back then. So, I think this stuff referenced here as "Apollo 19/20" is a fake, as is so much that I see posted on the internet.
Myself, I do not post fake stuff. Whatever you see that I put up there, is real. That would be on http://www.txideafarm.com, and http://exrocketman.blogspot.com. There's a bunch of how-to stuff for manned landings on Mars posted there on "exrocketman" in recent months. 60-ton-class manned Mars landers are very easily feasible, as long as you break out of the "rut" of prior hardware practices.
In particular, you must dispense with aero decelerators on Mars, and go straight to rocket braking for your landing, once you "pop out" of the high-heating hypersonics at about Mach 3 (local). There's no point to chutes or ballutes or any other aero-decelerator concepts: you "pop out" too low to use a chute at high ballistic coefficient, even at very shallow entry angles.
GW
The two largest oil finds in history were North America and the Middle East. All the other finds since have been far smaller. Even the things speculated about (like the Arctic) are figured as far smaller. That's just an unpleasant fact. Even the new oil boom in the US Williston Basin is only about the size of the Alaska North Slope find, and that peaked in 15 short years, although it is still in production.
Another unpleasant fact: he who has the most oil to sell has the greatest influence on its price. That's been OPEC since US production peaked about 1970. OPEC formed in 1963 specifically to be a price-fixing cartel. That's what they do. I watch what they do, rather than listening to what they say. Truth really is not a premium item in most Middle Eastern countries in recent centuries.
A third unpleasant fact: western civilization was "designed" by the dead hand of Adam Smith to run on cheap fuel. Fuel is no longer cheap, so things don't "work right" anymore. Since 1973, every major economic downturn has correlated to inflation-adjusted fuel prices at or above 150% of what appears to be the long-constant supply-and-demand value in a market not limited by supply (on top of which speculator "bubbles" and cartel punitive-pricing events get superposed). Good times are associated with the lower supply-and-demand-driven prices. Government policies seem to have had very little to do with any of this (bad news for you political activists and ideologues out there).
A fourth unpleasant opinion: the Middle Eastern fields may be peaking in production the way US peaked in 1970. This is a suspicion, not a confirmed fact. It is based on the observation that Saudi production levels in recent years have been lower, but have never exceeded, their 2004 levels. That's a bad sign in a world where demand is skyrocketing as China and India industrialize. If the speculation is true, then from this point forward we live in a world where supply always falls short of demand, so that prices spiral rapidly upward, even without the effects of speculator "bubbles" and cartel punitive pricing.
A fifth unpleasant observation: it seems to take about 40 years for one industry to fully replace another, looking at history, such as petroleum vs whale oil. There are many examples. You just don't do this in a handful of years.
Substantive conclusions: We should have earnestly started finding a replacement for oil about 40 years ago, instead of screwing around making scads of short term profits on something we knew was ultimately finite. Now it looks like we face about 40 years of chaos, war, and economic depression. That's the price we are going to pay for allowing money to influence public policies (no matter whose or what form of government) to the exclusion of ordinary common sense, or any notion of the public good.
GW
The Italians are not known for a justice system that produces rational or fair results.
GW
Those are some very odd-looking rocks in post 181 just above. I'd swear they look like lakebottom black mudstone that's been broken up and eroded in some fashion. Wind erosion produces really odd patterns and textures like that.
I see that kind of black lakebottom ooze in farm tanks and small lakes here. It is definitely organic life-produced detritus here. There's usually too much algae in those bodies. That black ooze bottom material really stinks. A lot of (but not all) the organics came from the rear ends of cows.
GW
I'm not entirely sure, but I think this is based on breeding U-233 from Th-232. They spent the last decade or so working on this. You have to start by using the U-238/Pu-239 cycle to breed your U-233 from Th-232, until you can stockpile enough U-233 to shut the U-Pu cycle down. The Indians have been working the final reactor design and the U-233 issues in parallel. Looks like they're just about "there".
BTW, nearly everybody has a lot more thorium than uranium. This is not the first time somebody proposed to do this. The Canadians proposed this unsuccessfully in the 1950's. It was no-go because the militaries of the time needed weapons materials, which this cycle really does not produce very well. U-233 can make a bomb yes, but you use a lot more, and it's bigger and heaver.
GW
News story seen today on NBC news "space" topic: Krunichev in Russia is pushing ahead with a reusable flyback booster strap-on. This is for vertical launch rockets. The booster strap-on is a liquid rocket (LOX and kerosene or methane) unit with tail fins and tricycle landing gear. One version has a swivel straight wing. It stages off about 30 km up at around M7, and falls back to winged lifting flight at about 12 km (if memory serves). Then it cruises back on turbojet propulsion to the launch site, and lands horizontally as an airplane.
This is a concept seen at airshows as a mockup for some years now. It was also a topic of conversation in multiple threads here before the last server crash. One of the variants of this that I have explored is an integral rocket-ramjet strapon that stages around 70,000-80,000 feet and M2.5-toM3, based on simple pitot-inlet ramjet technology. Such a thing would integrate well with current acceleration practices for vertical launch rockets.
The article said NASA had looked at similar ideas, using the rocket engines to cruise back, instead of a turbojet package.
The fallback does require proper treatment of nose shape and construction for hypersonic but well-suborbital re-entry. And perhaps several other surfaces as well, but that was not mentioned.
If sufficiently simplified so as to require a small logistical tail on the order of a battlefield weapon, this could lead to significant launch cost reductions. We already know small logistical tail has a huge effect. Here is a chance to see if lower manufacturing cost could provide similar benefit.
GW
The eskimos dealt with the old age problem by pushing them outside to die in the cold. On Mars, this is pushing them out the airlock without a suit. It is a problem that must be dealt with, somehow.
This problem is precisely why I do not think a one-way mission is wise anytime soon.
GW
It is very clear viewing RobertDyck's powerpoint that he knows his chemistry and his chemical engineering. If he says we can get aluminum from bytownite on Mars, I believe it! Great news, Robert. Aluminum metal is one very useful material. (What about iron and steel?)
I am no chemist or chemical engineer, the bulk of my training and experience is mechanical/aeronautical. But, in an environmental clean-up situation, I once used ammonia solution (at about 5% strength) to neutralize battery acid (sulphuric acid) that had flowed to inaccessible locations in building wall and truck trailer structures, in a battery acid spill incident. I kept it very dilute, because I was afraid of steam explosions, pouring this stuff directly onto spilled battery acid.
It worked, and far better than the "standard" treatment of spreading powder lime. Plus, the reacted product was just very-slightly-salty water, which we could dilute further and just send down the storm sewer. That clean-up effort was actually far easier and less labor-intensive that way. Spreading lime makes a horrible mess. Plus, we couldn't effectively get lime into the building wall internal structures where the battery acid had flowed, or down through the truck trailer structures where it got to.
We bought industrial ammonia solution concentrate at 10% strength, and cut it half-and-half with water on the job site. I saw bubble formation, but no violence. Sure were a lot of poison fumes inside that truck trailer, though. Time inside was basically limited to breath-hold times. But we got it cleaned it up. The building was better ventilated.
That was an interesting day.
GW
Question: Does it really matter in the long term, if some Earth bacteria got to Mars on these probes? Because, in the long term, men are going to go, and maybe even stay. That will introduce Earth organisms to Mars, even if nothing else before did.
GW
I'm no geologist, but sure looks like some kind of mudstone to me. It's had some kind of history with water post-deposition, for sure.
GW
I was very pleased to see a successful Dragon flight in spite of an engine out. In the absence of details, I do not understand the NASA safety rule forbidding second stage restart after a first stage problem. That caused the loss of the piggyback Orbcomm satellite, not anything to do with the Falcon-9. Bureaucracies, bah, humbug! That's why Spacex is looking for its own launch site. I hope they pick south Texas.
On the other hand, Spacex will have to get to the bottom of the engine out, even if NASA were not breathing down their neck. Something leaked somewhere upstream of the throat, that's how you get a pressure drop. Leaks get catastrophic in a tiny fraction of a second, that's why you need an automatic way to detect them and shut down, at way-faster-than-human speed. Looks like the controls on the Falcon-9 do exactly that. Bravo and kudos to Spacex for getting the safety/failsafe things right!
Leaks ahead of the throat show more pressure loss than thrust loss, at least initially on the transient while the hole is still small. Leaks downstream of the throat will show as thrust loss with no chamber pressure loss at all. You'll have to be monitoring thrust, as well as pressure, to detect leaks in the bell downstream of the throat. I would hope they know to do that. I would guess they are doing it, based on how well they have done the rest.
Leaks in either place cause errant hot gas plumes and shedding debris that very quickly damage adjacent engines or other structures. You have to worry about both phenomena.
BTW, what I said about engine and nozzle leaks applies to all rockets, not just liquids. Solids and hybrids, too.
GW
Typical Texas. Wore a coat (not a jacket, and actual coat) yesterday. Today, short shirt sleeves. It's been like that all my life.
That conflict between hot and cold air masses is why the US Great Plains has the absolute most violent weather on Earth. Texas is at the south end of that. It's called Tornado Alley.
I'm no meteorologist, but I do understand a few things about the weather here. Unlike the TV weathermen, I actually look out of the window (sound of laughter). They say we might get rain later in the week with another front. The little weak one tonight brought clouds but little else. Still quite warm out there.
I'll believe rain when I see it. Around these parts, a "six inch rain" is raindrop splatters 6 inches apart on your windshield. (More muffled laughter. I'm trying to be funny. Apparently unsuccessfully.)
GW
Yep, we got a norther. It didn't look like the stereotypical blue norther here, because the approach speed was so slow, but we sure did cool off nicely. It was almost 90 F here during the afternoon before the front hit. That front came through sometime after midnight. It was nice and cool Sat, even a bit cooler today (Sun). They say we're headed back to near-90 F by week's end. Typical Texas.
GW
I have no idea what a "magnetic plasma ramjet" is in Sark0y's post 47 just above, but you can use chemical ramjet, chemical turbojet, and chemical rocket propulsion together, if you wish, in one vehicle. I have less faith in combined-cycle engines, and more faith in just using two or even three separate types of well-developed engines run in parallel.
For a skip-glider limited to Mach 3, turbojet/ramjet is good enough to get the job done. I am not at all sure about the economics, but I am sure they would be better than sustained Mach 3 cruise in the atmosphere. Both engines burn the same kerosene or kerosene-like fuel (even liquid methane or biodiesel). You get to reject air friction heat while exoatmospheric on the glide. At Mach 3, you can do the skip atmospherics with a metal airframe. Stainless and titanium skins seem adequate, based on prior experience. You could up that to Mach 5+, but no more than Mach 6, using Inconel skins, as in X-15, but those are pretty heavy.
For the single-stage rocketplane ballistic vehicle, the velocity requirements are just too high for large payload fraction and a large structural fraction at the same time, which is required for economics and safety-of-flight. That speaks to nuclear Isp levels. The final form of NERVA ca 1973 was pretty well free of core erosion, which means it was pretty well free of exhaust plume radioactivity. That's quite an improvement over the earlier Phoebus and Kiwi experiments.
The problem is reentry at destination. Is the reactor turned off? That's a little safer, but you still must deal with core containment in the event of a crash. If it is off, you're deadstick, so how do you handle emergency needs to divert to another runway or to go-around? This is a big heavily-loaded airliner full of people, remember? While an intriguing and promising technological approach, there are some serious design and safety issues here.
The solution might be a gas-core reactor concept, something not out of the academic lab demo stage. But it could be. I'd suggest the open-cycle approach as the lighter of the two (the other being the "nuclear light bulb"), which also automatically has no core to contain when you shut it down. But, you have to accept a radioactive exhaust at the launch site if open cycle. How bad? No real data, but consider LH2/uranium (-235 or -233) mass flow ratio 30:1 is "perfect" containment at the nuclear burn-up rates needed. There's an upper bound estimate of the daughter-product "fallout" you spew. Those are much more benign if you use Thorium-bred U-233. Or so I hear.
If you go with "nuclear light bulb" instead, the exhaust is clean, and you dump the core at burnout in space, retaining nothing on board. Unfortunately, that core dump takes place at suborbital speed, so it comes down very quickly. Just on a different target. Or, you land with a retained core, just like the solid core engine. Take your choice.
GW
If your greenhouse is a tall structure anyway, why not rack your hydroponics vessels above your soil-based agricultural activity. Racks should be easy to build on lower-gravity Mars from most anything. Even lashed bamboo would work, which could be grown there. Including bamboo fiber-based rope for the lashings. A rope-making machine is a very old, very simple technology. You do need to know your knots and your lashings. Not in the usual astronaut training, but maybe it should be.
Think a round foundation in the middle of a small crater or depression, a mushroom-shaped building with a regolith-covered cap for a radiation shield, and clear walls around the "mushroom stem". Surround the thing to the poleward and sunrise-sunset sides with reflectors made of aluminum foil bonded to any convenient substrate (including even permafrosted regolith) as a 3/4 ring solar reflector bringing light inside the building laterally. You can mount your solar thermal and solar PV stuff up on the roof.
Over on the equator-ward side, that's where you set your very large water tanks. They are both your supply and a huge thermal mass. Paint them flat black, and let them be passive solar to the extent possible. It works in my greenhouse here. The other 1/4 ring of reflector surface on the equator-ward side would help amplify the water tank passive solar effect, but also blocks surface access to the building. If you need a roadway in, put it there.
I'm not sure what to make the transparent walls of, but eventually some sort of glass should be possible there, if the right silica sand can be found. I'd recommend a double or even triple wall for the insulative heat trap effect, and for decompression safety.
Comments?
GW
That's a very unusual-looking rock depicted in Vincent's post 162 just above. I swear I've seen rocks with dissolution pockets like that in limestone caves. Any idea what it's made of? That sure resembles water-based dissolution as seen here. But, limestone ???? There? What a good target for the laser and spectrometer!
GW
Vincent is correct about the likelihood of transient liquid water on today's Mars. In context, "transient" could refer to a time constant ranging from minutes to centuries, depending upon circumstances. I have seen lots of evidence for liquid water in photos from several sources, for some time now. It is quite obvious that there are transient outflow streams occurring on Mars today. The source is likely melting of subsurface ice in warm conditions. But no one yet knows for sure.
One should remember that in an atmosphere that tenuous (unlike here), there will be a very wide disparity between surface and atmospheric temperatures. Surface temperatures will lead the air temperatures in timewise variation, because of solar heating of a near-gray-body surface, while the "air" is a mere narrow-band absorber of relatively very-low effective absorptivity, even though it is CO2, the greenhouse gas. In the limit of zero "air", behavior is very much like that on our moon: very hot exposed surfaces in daylight, while there are very cold surfaces in darkness. "Air" temperatures in the boundary layer close to the surface will be somewhat closer to solid surface temperatures. The rate of surface temperature variation hot-to-cold and back is only limited by surface layer thermal mass relative to achievable heat transfer rates air-to-surface.
That being said, these water outflows are truly transient at today's air pressure on Mars. To be "stable" on time constants longer than a century, Mars's atmosphere would have to be dense enough that the partial-saturation (less than 100% relative humidity) partial pressure of water vapor would exceed the equilibrium vapor pressure of water at the local liquid pool temperature. For a liquid pool at 0 C, that is 6.1 mbar. For a warmer pool, that partial pressure is higher still, being the value shown in the standard steam tables. I have a psychrometric chart for Earth air that gives relative and absolute humidities. I don't have one for the nearly-all CO2 atmosphere that Mars has. But, in a crude sense, it would still be similar. It's still basically what an ideal gas can hold, at any given gas temperature. Hotter holds more water vapor.
All thermodynamics books and air conditioning handbooks have such charts for Earth air. I'm sure there's one in any edition of the CRC Handbook of Chemistry and Physics, if anybody wants to go look. (Try section F.) My best guess is that we wouldn't be more than half an order of magnitude wrong applying such an Earth air chart to Mars "air". But, somebody somewhere at NASA JPL has the corresponding psychrometric chart for Mars "air", or they would not be reporting a typical relative humidity of 0.3% on Mars.
All that really doesn't matter. The partial pressure of water vapor on Mars today is somewhere around a very tiny fraction of a single mbar. There would be wide geographic variations, including localized transients far higher around the outflow streams. But for "average" conditions, not only will small pools of exposed liquid water evaporate, they will do so quickly and rather violently. They'll approximate an adiabatic system and freeze in the act of boiling, in most locations on Mars under "typical" conditions. Local temperatures above 0 C only make the evaporation rate higher.
Yet in the past, conditions on Mars were far more Earthlike. The semi-fossilized gravel bar that Curiosity photographed is startling proof of that. Obviously, there were streams. That by itself implies lakes, perhaps even oceans. And, I suspect, microscopic life. Those microbes might still be there, underground. We found microbes like that deep down in the rocks here, only a few years ago. I'm not so sure about multicellular forms, as that took over 3 billion years here, and Mars only had about 1-2 billion years before it dessicated, froze, and lost its atmosphere. As best we know, anyway.
Dang, I wish that rover had a real microscope. Bacterial fossils here are very tiny, those odd little traces in the Allan Hills meteorite were even smaller. But, still crudely comparable. And the shapes were startlingly similar.
GW
Louis:
Very interesting study. Hydroponics is possible, for sure. I did notice that the microflora were acknowledged, but not really understood, based on what I read in that report. The focus of the study was obviously inorganic nutrients in the water and air. The bacteria and fungi counts they did almost seemed like an afterthought.
That actually sort-of makes my point in my previous post. There's a lot more to real farming than just nutrient chemistry. It's the symbiotic stuff that's the real make-or-break item. Always has been. The biologists know vastly more about that issue than I do, but I think they would agree with my assessment: we know a lot less about symbiotic ecology than we like to admit.
That being said, there are millennia of accumulated human experience with growing crops here on Earth. The bulk of it long pre-dates modern science, and still lacks a rigorous and truly-detailed scientific basis. The bulk of that long experience would suggest that our modern "green revolution", which is based on the heavy use of inorganic fertilizers, is a transient phenomenon, that it is not sustainable over multi-century timescales. I tend to agree, based on what little experience I personally have out here on this little ranch.
That's why I suggest we take the less-intensive, demonstrably-sustainable, "traditional" agriculture practices (that date back to the stone age) with us to Mars.
Why screw it up twice?
GW
There's more to fertile soil than just rock dust, water, and ammonium nitrate (AN). (BTW, AN is a class 1.3 mono-propellant explosive, even in fertilizer grade (a purity standard). Adding fuel oil just increases the yield. It is friction-sensitive, shock-sensitive, and can be induced to decompose (deflagrate) by heat; which in large-enough piles, can propagate into full detonation. Try justifying the shipping of THAT in interplanetary supply.) Any AN you use in agriculture on Mars needs to be locally produced. We know there's perchlorate salts there; there are probably nitrate salts as well. These are all evaporites.
You also need "organic matter", which is primarily animal/human feces, to mix with the rock dust, which feces contains both carbon-hydrogen-oxygen-nitrogen compounds plus real, live organisms (some microscopic, some macroscopic-especially in the third world). You don't have to ship the feces, any people on Mars, and any animals they bring, will supply more than can be initially used. Later on, we'll see. But in Asian rice culture, it seems to balance out pretty well.
Urine is another useful soil component, although it might prove useful to remove some of the salt first. The ammonia in it is fixed nitrogen, the very thing plants need most. Ammonia is actually better than AN in that respect, or else the mass of AN fertilizer bags would exceed the mass of tanked ammonia at rural ag-supply places; it does not.
On Mars, you are living in an environment that pressure-wise is very little different at 0.7% of an atmosphere from the vacuum of space. It should be very easy to build a vacuum flash still rig that could separate the most of the water and nearly all of the ammonia from urine, and so isolating the leftover brine as something to be disposed of by evaporation, preferably not in contact with the soil. Same thing might work in deep space travel. Not a closed ecology, but maximized recycling of what we can use.
The "clean" all-hydroponic thing as most seem to conceive it may well prove to be a technological dead end. Most of the useful plants we have are more symbiotic with the organisms in the feces than most folks want to admit. We are not yet capable of engineering plants that do not need such symbiosis long-term.
By the way, although I most definitely do not claim to be an agricultural expert, I have personally seen this process in action. It is quite real. I really do live on a cattle ranch in the midst of farm and ranch country. My wife is a trained composter. This is most definitely not theoretical knowledge from some school or some book. It is the real McCoy.
GW
The geologists tell us that the fossil record here on Earth is a very skewed sampling, and for a wide variety of reasons. Yet, what it seems to show is that life here was one-cell microbial for about 3 billion years, and may have begun almost as soon as liquid oceans formed, very shortly after the planet cooled enough to have a solid crust at all. How all of that life evolution interacts with changing climate and chemistry, and a slowly-dimming sun, is not well understood. But there it is.
This microbial sort of thing left only microscopic fossils, of similar size and form to the odd traces found in the Allan Hills meteorite, which rock came from Mars. Only in the last 660 million years or so does there seem to be evidence of multicellular life here. This is not conclusive, of course, but it does suggest that microbial life sprouts up quickly and easily in a liquid water environment, while multi-cellular forms may require a time constant on the order of 3 billion years, of benign conditions, to evolve. I could be wrong about that, but that's what the record here seems to say.
We have no reason to believe that the fossil record on Mars would not be as skewed as that on Earth, and probably for the all same reasons. There, like here, the geological record will be hard to interpret, especially any fossil record. What does seem very clear is that early Mars was much warmer and wetter, with similar conditions and chemistry to the earlier Earth. I'd bet real money it had microbial life, just like here. Maybe even the very same sort of life, if the panspermia hypothesis was a factor: the late heavy bombardment event could have spread microbes, or perhaps just their chemistry, between the two planets.
The problem is, from what we can tell, is that Mars too-quickly dried out (acidifying along the way), and froze up, as it lost its atmosphere. (For whatever reasons.) Apparently this was a couple of billion years ago. There might have been short warmer, wetter events since then, but that is not clear. My hypothesized 3-billion-year time constant for evolving multicellular forms didn't happen on Mars, as best we know. Accordingly, I would not bet real money on our finding macroscopic fossils. But, then, it's only a bet. No one yet knows.
I view putative macro fossils with a jaundiced eye, meaning I have a strong "show-me" attitude about that. There are so many ways for inanimate geology to create forms that look like life fossils, as we know. Putative microfossils on Mars I find much easier to accept, since the climate seems to have been hospitable to Earth-like life for a billion or two years, perhaps. I do think the NASA scientists who claimed microfossils in the Allan Hills meteorite were very badly mistreated by the scientific establishment. That would be one of Carl Sagan's few mistakes, reacting the way he did.
Here is what I predict: we may find microfossils of microbial life in sites scattered all over Mars. If we drill deep enough, we may, (I repeat "may") even find living microbes far under the surface, similar to deep-rock microbes found here recently. If we ever terraform Mars, that life may re-invade the surface and re-colonize it. I rather doubt Martian microbes could sicken us, or that our microbes present a threat to Martian microbes. The chemistry should be different enough after 2-3 billion years' isolation, to prevent any such compatibility, even if they had the same original panspermia source just after planetary formation.
All of that is just my speculation, of course. Enjoy.
GW
Wouldn't surprise me a bit to see mud polygons from an old lake bed. The public news media are full of the story about the fossil gravel bar in the steam bed.
There once was a time when Mars had a very much thicker atmosphere and warmer environment. Streams and bodies of water, all nice and "stable", just like here. The northern lowlands look an awful lot like an old ocean bottom, too.
I would think that old stream beds and lake beds would be very good places to look with a real microscope for fossil remnants of microbial life. Those odd traces in the Allan Hills meteorite might be a pretty good guide to the size and form of the things we would be looking for. Too bad Curiosity isn't equipped for that.
GW
I guess what I have been trying to say is that the triple point of water is but one point in the standard steam tables. If you read in the thermo textbooks what it says about those tables, then you understand that what is tabulated there is values of pressure and temperature at which condensed and vapor phases of a PURE SUBSTANCE can coexist IN EQUILIBRIUM, with both (or all 3) phases at the same temperature. (Caps are for emphasis only, I'm not shouting, please don't misunderstand!)
They make an assumption in these books of a simplified model to use these in the presence of a SECOND SUBSTANCE, i.e., the gases in an atmosphere that can get humidified, up to a maximum, by the water vapor. That simplified model says (1) the atmosphere is a mixture of ideal gases (far from triple point), and (2) no gases dissolve into the water or the ice. There is a 3rd thing, but I forget now what it was. I'm getting old, so please excuse my failing memory. I first studied this subject over 4 decades ago.
But, everything is assumed to be at equilibrium. The gas laws say the total atmospheric pressure is the sum of the partial pressures of the water vapor and all of the ideal gas mixture components. Equilibrium says the water vapor pressure from the steam tables is the water vapor partial pressure in the atmosphere. If it cannot meet this ncondition, it cannot be in equilibrium: it can still exist, but it cannot persist.
We typically mis-use this model here on Earth to compute a water vapor pressure above a pool of liquid water, with a different air temperature. The vapor will mix into the air, and the gases will dominate the mixed gas-phase temperature, so that the vapor and liquid are not at the same temperature. Yet, it is still pretty accurate to do it this way. Weathermen do it all the time, and quite successfully, I might add.
The "hard" part is equilibrium, which is never approached very closely in the real world, either here or on Mars. The low vs high humidity disparity drives evaporation speed, yes, which is an inherently nonequilibrium process. Here, because pressures are near 500+ mbar even on the mountains, there is usually plenty of "room" in the total pressure for 100% relative humidity, regardless of the liquid pool temperature, except for very frigid air temperatures. That gets limited by the max absolute humidity.
Having "enough room" for triple-point levels of partial vapor pressure is not ever true on Mars. At the 0 C triple point, 0 C liquid water AT EQUILIBRIUM would require 6.1 mbar water vapor partial pressure above it not to evaporate, perhaps violently. The total atmospheric pressure on Mars is only about 7 mbar all over the lowlands. That's only 0.9 mbar CO2 pressure, something we know cannot exist on the lowlands, because we already know the Martian atmosphere is very dry (0.03% relative humidity typical), and measures about 7 mbar total. You might violate that in a transient very locally, but as the winds mix it into the atmosphere generally, it cannot persist with that much water vapor.
That CO2 cannot hold very much water vapor without water condensation, even if it were as hot as our air. Same is true here with our air. That's the dew point, and it sets a limit on how much water vapor partial pressure you can really have at equilibrium. The colder the gas, the smaller the absolute humidity (water vapor partial pressure) you can have, right down to the triple point.
If your max allowable-by-humidity water vapor partial pressure is under 6.1 mbar, then even a 0C pool of liquid evaporates by boiling, no matter what the total atmospheric pressure is. Those conditions exist today on Mars. You can temporarily have a stream or river by any conceivable means, but it is not "stable" in the sense that it is boiling away (some of that vapor likely falls as snow nearby, but even that sublimes later). Eventually it is gone, unless you have some means to replenish it at or above the loss rate.
Same is true for 0 C ice: if the water vapor partial pressure is under 6.1 mbar, the ice sublimes. The vapor mixes into the far more massive atmosphere (thin as it is), and essentially is 0% of the total. That's why all the ice the landers have dug up has sublimed away in a matter of hours to a day or so. In that sense, water ice is not stable when exposed to the Martian atmosphere. Any exposed ice we see there has either been uncovered recently, or was very much larger in size in the past. You cannot get away from that picture.
Sometimes, in some places, it gets above 0C air temperature on Mars. (Actually, the surface regolith will warm more reliably in the sunlight than the air, because that air is so very thin.) In any event, a piece of ice might melt and form a puddle of water. Temporarily. That puddle will evaporate, and rather quickly. I think it will boil, and may actually freeze in the act of boiling, just like a dish of water in a bell jar that you pump the air out of. Then, left in near-vacuum inside that bell jar a while, the ice sublimes. You may get frost elsewhere in the bell jar as this happens, due to absolute humidity limits. Same happens on Mars, except it's all out in the open.
To make exposed water or ice stable on Mars, the CO2 atmosphere must be very much thicker. The total pressure must be high enough so that the dew point absolute humidity corresponds to a minimum of 6.1 mbar water vapor partial pressure. I don't have a hygroscopic chart for a CO2 atmosphere, mine is for air. But it's exactly the same idea.
That being said, the Martian air has indeed been very much thicker in the past. Perhaps only a few million years ago, certainly about 3-4 billion years ago. How else could there be lake and ocean shorelines and dendritic river channel systems preserved on its surface?
I think we're seeing transient phenomena associated with both water and CO2 on Mars. That's clouds and snow. Not much in the way of liquid water other than some very transitory dewdrops, and most certainly no liquid CO2.
Just offering my humble opinions. But I do know my classical thermodynamics. Even if I forgot that 3rd thing above.
GW
Recent news stories indicate they have photographed carbon dioxide snow falling on Mars. Definitely CO2. I suspect water ice deposits have been where they are (and shrinking as they sublime) for a long time. Since the last time the atmosphere was a lot thicker. Whenever that was.
Not surprising that CO2 snow happens, given a CO2 atmosphere and the cold temperatures we see reported. Actually, the large swing between very cold and quite warm is not surprising, given that near-vacuum of an atmosphere. On the airless moon, the swing is even further. It is definitely not a place like the Earth we are innately familiar with.
GW
I got to go to the 1st ISAF planetary defense conference in Granada, Spain in 2009. B612 and many other groups were well-represented there. I got to have lunch with Rusty Schweikart at that meeting, and spent a delightful evening chatting with former cosmonaut Dumitru Prunariu, as well.
Didn't get to go to the second one in Budapest in 2011, but I'd bet B612 and the other groups were there, too. The risk is real. I think that asteroid defense is a very viable and compelling reason for a much better spaceflight capability than anybody has right now.
Sending one-way probes just about anywhere in the inner solar system is just about as easy as going to the moon one-way, in terms of delta-vee requirements and launch rockets. The size of your payload sets the launch rocket requirement, and we have some fairly big ones now. Atlas-V looks pretty good in the 20-25 ton size to LEO, significantly smaller for escape. Falcon-9 looks good in the 10-ton range to LEO, and Falcon-Heavy is supposed to fly next year (53 ton LEO).
The reason manned missions are so much harder is both the mass of the return means, and the mass of all the life support. We see the same effect of mass-of-return-means even with unmanned sample-return missions. Because of the logarithmic/exponential nature of the rocket equation, the departure mass compounds very rapidly to very ridiculous figures for the one launch/one mission model.
During Apollo, they ignored assembly and refueling in LEO as immature, but they did do lunar orbit rendezvous (a lander) based on the docking experiences with Gemini, which got them down to one Saturn-V launch per mission. There's even more launcher size-reduction potential with assembly/refueling in LEO, which we used to assemble the ISS.
One thing I have noticed is that commercial-market launchers are cheaper to launch (and cheaper per unit of payload if flown at max load) than anything the US government has ever developed or operated (that's NASA, USAF, and US Army, even USN). This is the commercial competition effects driving the builders toward simpler systems with much smaller logistical tails supporting the rockets. That tells me that you are better off choosing something from the existing stable of commercial launchers, than developing a gigantic rocket for which there is no commercial application. But it also inherently means that you use assembly/refueling in LEO.
Assembly by docking of easily-launchable modules is mature. We built a 450-ton ISS out of things around 15-20 tons max. We're just getting started doing refueling in LEO, transferring storables at ISS. There's a lot more to do before transfers of cryogenics in LEO is a mature technology. Which is a really worthwhile technology development for a government space agency to pursue (though none seem to be doing it).
Given a mature refueling technology in LEO, and a change in mindset away from the "traditional" one launch/one mission model, manned missions anywhere in the solar system become technologically "easy", just a matter of expense proportional to departure mass from LEO. The 1950's idea of the orbit-to-orbit transport, with landers as needed, really is the best way to do the big manned missions. If you recover parts (or all) of the transport in LEO, you get to use it again (refueling), which cuts expense dramatically over the useful lifetime of the vehicle.
But, you don't design it fragile just for light weight on a one-shot trip. You have to design it for long life and robust survivability, to be re-flown dozens, perhaps even hundreds of times. That's the kind of hardware you have to launch and assemble. It's quite a different mindset, and quite a different style of engineering.
Nuclear rockets really help with this sort of thing, too. For the transport and the landers. Too bad we don't have any ready to fly. We once did.
GW