Yet another perspective: From http://water.usgs.gov/edu/wateruse-total.html in 2010 306 billion gallons of fresh water per day used in the united states. Volume of Lake Superior is very roughly 3,000,000,000,000,000 gallons.
V Lake Superior / (306 * 10^12 * 365) = 26.86 years
About 27 years of entire US water supply assuming no water cycle. Now that I do the math (hopefully I didn't screw it up), I'm not sure that's a big number or a small one actually.
Its big... take in account the inefficient water management that we have and that a martian colony would be numbered in the thousands, at best. This is basically unlimited reserves!
That lake is not just huge, but crazy deep. It's bigger than the state of Maine in terms of area and in places is deeper than the Empire State Building is tall.
Or in other words, imagine turning Maine into a fishtank forty stories high that's full of fresh water.
Solar wind strips that atmosphere very slowly over geological timescales. If we terraform Mars, then we probably have the technology to replenish it faster than that loss.
...because we don't need to? Earth is already full of plant life. Mars isn't.
Sorry for the overly blunt answer, because I know this isn't the question you're asking, but IMHO the question you're asking is based on a ridiculous premise.
We are polluting the Earth. Yeah, this is really bad for the Earth, and for us, but it isn't going to kill all life here. The thing that a "backup planet" is here to protect against is something like being struck by a meteor, or a plague, or nuclear war. Something where everybody dies very quickly, not something where life changes radically.
If you want to terraform Mars, it's probably not because you decided Earth was beyond salvation; I haven't heard many people wanting to abandon Earth. Most people in favor of terraforming Mars want to have a 'backup' for intelligent life, or want to begin humanity's expansion past the bounds of Earth's atmosphere. The 'backup' motive is comparable to suggesting someone backup their electronic data instead of just trying to get very reliable drives.
I am also not sure that it is possible to 'terraform' Earth. 'Terraform' means 'to make like Earth', and Earth is as Earth-like as is possible, no matter how hot or cold it is.
Humans have been terraforming Earth for at least the last hundred years (industrial scale) to 10,000+ years (agriculture, livestock, extinction of other species).
Without a magnetic field, there is way too much radiation on the surface of Mars. A colony would pretty much need to live underground. If you are going to live underground on a planet with unusably-thin air, why not live on the Moon instead?
Instead of just asking the question that many people think they have answered, why not say what you don't like about their answers?
For example, Elon's speech about Mars colonization gives one answer. Maybe you've got great reasons to disagree with him. Maybe there's someone else you'd like to reply to?
(Hint: folks advocating for Mars think the atmosphere is not unusable.)
Not quite sure what you mean: I was responding to a question asking why it would be nice to have a liquid core. In other words, I was commenting on the radiation question.
To hide from Radiation, one plan is to have 16 feet of soil on top of the habitat [1], and limit outdoor time to just 2 hours a day. Given those levels, I'd argue that it would make better sense to build entirely underground on the Moon. The Moon has a shallower gravity well, much stronger solar flux for power, and is much closer for resupply.
There are places on Mars where water ice is available year-round, and carbon dioxide ice seasonally, at high latitudes. Therefore, I'd say this discovery, at low latitudes, has few implications for colonization unless there's a fair bit of carbon dioxide ice mixed in. So I'm waiting for word on that before getting too excited.
You're going to be hard pressed to out pedantic NASA scientists. They probably spent quite some time deliberating over the term "Ice Deposit" as the most accurate one.
There is a sentence that seems to imply that the frozen status implies there is no life. I'm not so sure we can be sure of that. There are microbes on Earth that basically live in virtually frozen environments. (All you need are moments when the water is liquid.)
All you need are moments when the water is liquid.
But you don't get those at such low atmospheric pressure. Mars atmospheric pressure is around 600pa. Below 611pa, the boiling point of water drops to the freezing point; you can have ice or steam, but not liquid water.
An unsealed hole underground would have to be dug to the same depths as that crater. If you're pressurizing it, you'll probably target 1 bar to live in it, instead of 600 KPa.
A glacier that has the pressure to melt ice, would have more than enough pressure to keep it from sublimating. A rough estimate says that a foot or so of ice could provide over 600KPa of pressure, but that doesn't account for any means of keeping the water liquid or the ice solid. However, I wouldn't expect to actually find that on Mars. You might be able to keep water that way for a while until it froze again.
They do have recent satellite images that appear to show signs of water running down ravines at certain times of the Mara year. Don't have a citation handy, though.
You could even just have life that moves more slowly because of the lower available energies. If we ever find some life that does not have an Earth origin perhaps we can finally get some more data points about what environments are really required for life.
It is not mud. Firstly it is not liquid, it's frozen. Secondly, it's not permafrost where it's mixed with a considerable amount of dirt, it's ice, a sub-surface glacier, one of many on Mars, merely the largest one we've discovered so far.
This should be enough for a colony though. With a recycling program it would probably last indefinitely. Much better than bringing the water from Earth.
Recyling could mean never letting it out into the atmosphere in the first place. Or maybe would, since there is no water cycle to talk of on Mars. Think closed-loop aquaponics systems etc.
I mean that water if going to be the least of your problems, unless you've mastered terraforming (we haven't) or you're okay with living under a huge dome (that we don't even have technology to build, either). Liquid water cannot exist on Mars, and liquid blood can't either, so you would die horribly if you went on Martian sole without a spacesuit. Apart from having gravity, living on Mars would be like living on the ISS, minus the food they bring to the station from Earth...
