Where did water originate?
(I didn't know how to format that question any better, so please forgive the fumbly format)
It's believed that Mars' atmosphere was considerably more dense than it is today, but along the way, its core cooled, and it lost its protective magnetic shield, allowing the solar wind to strip away much of its atmosphere.
I don't know what you mean by "too far removed from current capabilities", but I doubt we'll even start working on the problem for two or three centuries.
No, it seems more likely to me that we'd use our growing knowledge of genetics and psychology to hack out the part of ourselves that needs to be outside, and opt for a purely enclosed existence on Mars.
However, the thought of a telescope-quality mirror 250x the size of the JWST is pretty amazing :)
Mars receives 593 W/m^2 flux, so each IKAROS-sized reflector could produce about 100 KW of energy. Given the expected difficulty of large scale terraforming and colonization efforts, it seems the cost of, say, the equivalent of 10,000 IKAROS-sized mirrors (~1 GW, comparable to a large nuclear plant) would be relatively minor.
Whether that would be more cost effective than shipping an equivalently powerful reactor or other generator is questionable - it will presumably depend on our lifting capacities.
So you also couldn't just vaporize the ice, you need to split it up. Solar heat could be sufficient, but the water will then be missed everywhere else on mars where life wants to grow.
And Mars is dry.
So I would first use the water in enclosed habitats. And then after, if there is plenty of water left, one could start to think about smoking that up ..
But there might be other options, once you have lot's and lot's of autonomous machines and rockets available and allmost unlimited fuel (sun?). But without that? Not a chance ...
The notable benefits from such an approach would be the ability to easily deliver asteroid-based water deposits (aim it at Mars, let reentry do the rest), as well as the significant simplification of ground based colonization technology - it's far easier to build resilient habitats for a non-breathable atmosphere than it is for a vacuum, and the risk of accidents and difficulty of venturing outside is much, much lessened (a face mask or filter and oxygen tank instead of a bulky spacesuit), not to mention the radiation protection afforded by a thick atmosphere.
But it has to be carefully considered, as it might hinder a longterm plan for a nice, breathable atmosphere.
But once we reach mars, we are probably busy first, with primitiv things such as life support ...
we could also bore into those tunnels and put caps on the hole afterward, have some of those channel light into those tunnels too.
Someday though we may be able to breathe on Mars
Off topic but I’d like it quite a lot if people could be informative without being eviscerating lol. I suppose this doesn’t usually happen, but it should happen more. That’d be so much better, so much more tolerable and happier. It’d be good for all of us probably lol.
What Would Feynman Do?
In this case, I'm imagining he'd say these are some of the things we think might explain bodies' keeping or losing atmosphere, but we have to remember that almost everything we think we know about planets and moons comes from looking at the light that bounces off of them and making guesses about the underlying rules, but we still don't know do much about the underlying rules of physics, so there's probably more that we don't know than what we do know about atmosphere retention.
PV=nRT. T is temperature.
Titan is not only protected by Saturn's magnetic field, but it is also very cold. Some of the molecules that are gaseous on Earth are liquids on Titan. Cold gases have lower pressure, and less likelihood of bouncing a light molecule high enough up in the atmosphere that the solar wind can grab it and blow it away.
Earth has a hard time holding on to light molecules like H2 and He, but its He is replenished somewhat by alpha decay, and it takes a long time to get from the inside of a rock to the upper reaches of the atmosphere. Most of the hydrogen is attached to heavier molecules. But it happens eventually, and even the Earth's magnetic field and gravity can't keep them. Venus is almost as massive as Earth, but it is hotter than Mercury and has no core-generated magnetic field. So most of its water has already thermally dissociated (which happens slowly starting at around 800 degC) and the H, H2, He, and monoatomic O bounces high up into the atmosphere, ionizes, and blows away. So now Venus has about 90 bar of CO2 and barely any water left.
One of the terraforming proposals for Venus is to transport a large quantity of hydrogen from Jupiter to Venus, and use Fe catalyst to react it with the CO2, to get graphite C, H2O, and O2. That would strip off much of the greenhouse blanket, but the planet would still have to be cooled off and protected from the solar wind to keep all that hydrogen around on a geologic time scale.
There's not much left because it mostly boils off due to low pressure, but in dark crevasses it's likely to stay cold enough to remain condensed. It's been measured spectroscopically.
I think the concept you're thinking of is free energy, which determines the final destination of a process. The equation relating these things is (change in free energy) = (change in energy) - temperature × (change in entropy). Entropy only becomes the dominant component when temperature is high. And, as expected, water molecules dissociate at high temperature.
In any case: dH=TdS + Vdp note dp is small in space but V can be large and dS is the change in entropy.
...and enthalpy of ideal (interstellar H & O) gases does not depend on pressure, unlike entropy and Gibbs energy. If you really just mean free energy U, then they are basically the same thing in open space (but not in a plasma), a distinction without difference.
For further pedantics I recommend Wikipedia, since I doubt we are helping anyone else.
Water is fairly abundant in the universe. As are alcohols.
-- Ian Banks
Oxygen is pretty common and hydrogen is everywhere, so water (as ice) is not scarce in the universe. The only place where water is uncommon is near a star, like us, where the water boils off into space unless a planet has enough gravity to hold it in.
Hydrogen comes from primordial nucleosynthesis [1] and makes up most of the interstellar medium [2]. Oxygen is produced when neutron stars collide and stars explode [3] as well as when some stars burn [4]. These freely combined in the gas disk from which our solar system formed, condensing into planets, moons, comets and other things [5].
[1] https://en.m.wikipedia.org/wiki/Big_Bang_nucleosynthesis
[2] http://casswww.ucsd.edu/archive/public/tutorial/ISM.html
[3] https://www.chemistryworld.com/news/heavy-elements-forged-by...
Also, we seem to have a lot of water. It's really all from comets, a little here, a little there?
We’re not sure from where Earth’s water came [1]. Some evidence suggests the Earth was born with all its water, some that most came from comets.
[1] https://en.m.wikipedia.org/wiki/Origin_of_water_on_Earth
The water on Earth may seem to be a lot to us on the surface but it is only about 0.02% by mass [1].
https://www.universetoday.com/65588/what-percent-of-earth-is...
So at the time of the formation of the solar system, the whole area was a big gaseous cloud of supernova debris with lots of ice. The ignition of the sun started the frost line, and pushed volatiles out of the inner solar system. However some had already been trapped in the formation of the planets, and rose to the surface as they cooled. That's where Earth's ocean came from, and we know Mars and Venus had oceans too. Presumably also Mercury, although I'm sure that was short-lived.
So yes, it's all from cometary material. But then ALL of the Earth is from cometary material, and the oceans only make up a small amount of the Earth's total mass.
So in a stellar accretion disc, much of the water will end up inside the new star, and dissociate, but quite a lot of it will gather in the planets, moons, and comets. Europa, for example, has about 2 or 3 Earth-oceans worth of water. Uranus and Neptune likely have solid cores composed mainly of ices that include water ice.
The discovery of photosynthesis caused the "great oxygenation event" which pumped oxygen into the atmosphere. Oxygen reacts with atmospheric hydrogen to form water. Without the oxygen, the very light hydrogen molecules would float to the top of the atmosphere and are easily blown away by solar winds, which is what happened on Mars. But with high oxygen concentrations on Eath, hydrogen molecules react to form heavier water molecules before they have a chance to be blown away, and thus hydrogen and water are retained.
I read about this in the book "Oxygen" by Nick Lane.
His point in this new article is that instead of one big "oxygenation event" there may have been multiple. But he sticks to his story that the creation of an ozone layer by photosynthesis was the key step in saving the oceans. He argues both Mars and Earth had oceans originally (confirmed by Mars Satellite observations), which were gradually diminished by a process in which ultraviolet light splits atmospheric water, minerals on the surface absorbed the oxygen (rusting, making Mars red) leaving the hygrogen to blow away. But life on earth pumped extra oxygen into the atmosphere, faster than minerals could aborb it, creating the reactive ozone layer which prevented hydrogen from blowing away, thus saving the oceans from their fate on Mars.
[1] nick-lane.net/wp-content/uploads/2016/12/Oxygen-and-life.pdf
I can't intelligently contribute to the overall discussion here, but I know one of the most interesting things about the currently understood timeline is the apparent lack of eons between the earliest conditions conducive to life after its initial cooling and the earliest evidence of life. Don't quote me on exact numbers, but within margins of error, as I understand it, it's like in the range of millions of years, not billions (which has all sorts of interesting implications for both the Fermi paradox and religious thinkers) Though, as far as I know, you'd still be correct on the distance to photosynthesis.
You forgot freeze.
gravity and magnetic field? if it were hydrogen or helium it would be stripped off by solar wind (storms) like everywhere else, but water is quite heavy due to the oxygen.
also 'everywhere else' means practically mercur, mars and asteroids (moon). no idea about venus. ice giants keeps their water also due to gravity and far apart on pluto it's frozen like rock.
Or not; the “land theory” (that it began in shallow, possibly volcanic, terrestrial pools”) and “sea theory” (that it began in oceans, possibly at hydrothermal vents) have been competing theories forever, essentially.
The same is true of earth and helium.
But where did water originate?
answers your question.
If you are trying to go back to "why is there anything?", then the answer is "we don't know precisely, but we do know that if those things hadn't happened, we wouldn't be asking the question, so so we have no basis of knowing whether it's random, rare, or a near-certainty for a new universe."
How many comets have hit us that were rife with water supplies to provide the amount of water earth has given that water isn't also abundant on planets that are much larger, like Jupiter?
Why do we see planets with atmospheres of say sulfer, and earth doesn't have an issue with sulfer in the atmosphere?
Most of the comets whose orbit intersects with Earth's orbit collided eons ago.
Some comets still enter the inner Solar System, of course, but it's going to be extremely rare for one to be on the right path to hit the Earth.
http://www.sciencedirect.com/science/article/pii/S0012821X17...