how thick of an atmosphere could mars realistically have?  can humans live in an ATM of 0.3?
829268
That's like living above Mount Everest.  No, it is not possible.\n\nhttp://bmj.bmjjournals.com/content/vol317/issue7165/images/large/abcoxy5.f2.jpeg
433514
Possibly, but i believe venus is a better candidate.  The higher gravity of venus (very earthlike) would allow it to sustain an atmosphere like ours if we can solve 2 other problems...more solar radiation, and a retrograde day that is months long.\n\nThe L.O.V.E. project (Life On Venus Enhancement) I made this up when i was a kid:  solution 1 - put lightweight, but very large reflectors into orbit around venus, on the day side they will block light in a 24 hour pattern, on the night side they will provide sunlight in the same pattern.\n\nsolution 2 - release into orbit around venus a cloud of particles to reduce the solar radiation and also use the reflectors/shades described above.\n\nAs the temperatures approach earthlike conditions, introduce water (capture a comet probably, or change it's orbit subtly to get it to venus.)\n\nIt's possible there is substantial water on venus tied up in some chemical situation or another, we don't know enough about it.\n\nand btw, for the other answers claiming mars is too hot, um, no?
1085010
You mean outside of a biodome? None currently show any promise of sustaining human life in an unaltered state. Most would be too cold, even Mars would be too cold most of the year, the only option is a enclosed biodome, like a space station on a planet, or through terraforming. Terraforming so far would be viable for Mars because of it's proximity and it's like an open ground, there's less in the way (Venus would be very difficult by comparison) outside that the best options appear to be Jupiter's moons such as Titan with a heavy water content and nitrogen.
65789
Temperature needs to be moderate so that water can exist in liquid form.  Gravity needs to be enough so that the liquid water doesn't escape into space.  An atmopshere is nice unless you like skin cancer and burnt vegetables.  Surface is not as important as the atmopshere.  Some rocky ground would be nice though.
274202
The temperature on Mars ranges from -140 C to 20 C (-220 F to 68 F) with the mean temperature being -63 C (-81.4 F).  While it may get mildly warm during the summer, Mars tends to be bitterly cold most of the time.
1069293
Flying a balloon on Mars is not easy. The ground-level atmosphere is (I believe) 1/140 times as dense as ours, and even with 1/3 of the gravity, it may be equivalent to flying a balloon at 25,000 meters on Earth or at 80,000 feet. It can be done, but takes a big balloon. With the fierce storms of Mars, one also wonders how long such a balloon would last. \n    About the lifting power--it equals to the weight of the displaced atmosphere, minus the weight of the gas inside the balloon, required to keep it inflated. Whether that is hydrogen or helium should make little difference, because either gas weighs much less than the air (or on Mars, carbon dioxide) which is displaces. Hydrogen should be available on Mars, if only a little water can be extracted there, which seems likely. Hydrogen was of course used in all the Zeppelins in WW-I and with proper caution is quite usable. \n\n    Oxygen and nitrogen are rather heavy, cutting the lifting power by a factor of about 4: considering how marginal any balloon is on Mars, they are clearly unsuitable.. \n\n    Scientific high-altitude ballooners on Earth prefer helium because of the way its temperature changes as the balloon rises and the gas inside expands, but on Mars a balloon probably won't rise far. Rubber balloons launched to probe the weather are filled with hydrogen, which is much cheaper: they rise quickly and explode at their maximum altitude, but by then all required data have been transmitted by radio.
299767
YES. The atmosphere is so thin you can't breathe. When the first astronaut, Alan Shepard, rode Freedom 7 in suborbital flight we sure thought we were going into space. All the hazards of deep space were experienced on that flight.
1046567
No, not really. However scientists have found traces of water present in some core samples. They generally believe that Mars did have oceans and lakes and an atmosphere like Earth. A very long time ago. I'm sure you could get all the information you need at the NASA web site.
676296
It's completely beyond our current science and technology to replicate the environment of Mars with such precision that we could be confident that we'd have the exact same (or even similar) conditions for life as exist on Mars.\n\nIn addition, how would we replicate Mars' environment when we know so little about it?  You'd need to send thousands of probes to Mars to get enough information to even *begin* such an experiment ... and by the time you'd finish that, you could've already run a full set of experiments on Mars testing directly for the past or present existence of native life forms.\n\nA planet's biosphere is an incredibly complicated thing.  It's something that scientists seem to only now be learning about our own biosphere, unfortunately a bit too late.
994713
MARS... quite possible
827505
No other planets are habitable for humans.\n\nMercury and Venus being far too hot.\n\nJupiter, Saturn and Neptune for being gas giants and so has no solid surface. The gravitational pull of these planets would crush our bodies. Juipters gravititational pull is over 300 times the earth.\n\nPluto is too far away thus seeing temperatures of over -200 degrees C.\n\nMars would have been a perfect candidate, as the temperature is quite similar to earth's at occasion. But our lifes need plenty of water and the abundance of water on Mars is basically zero.\n\nFor other life than humans, a moon called Europa, which orbits Saturn, contains frozen methane and water, which could harbour life. The only problem is its a moon and not a planet.\n\nThere are all the other planets (approximately 250 so far discovered) in the Keiper Belt which need to be examined
912759
Hey Visit \n\nhttp://en.wikipedia.org/wiki/Mars
393268
First to answer you second question: No we’re not terraforming Mars at present. Now for the first question: At this present point our technological development is woefully adequate to handle the issues of keeping this planet’s atmosphere from going into a greenhouse condition. Furthermore, it has taken by some estimate approximately 75 to 100 years for us to bring about this greenhouse climate change, which in a crude sense is a form of terraforming.\n\nThe idea that we could terraform Mars at this present time would be extremely impractical, it would cost hundreds of trillions of dollars, and it would take a very long time to see any results (on the order of hundreds of years). Plus you’d have to figure in the technology needed for such an undertaking, which although is probably available (with our technical capabilities), we’d then have to figure out how we’ll get it there. This would be no small undertaking. You have to remember that Mars has an atmospheric pressure that is less than 1/10 that of Earth and it has a very scant amount of water free-flowing on its surface. The vast majority of the water is locked up in the polar icecaps. Therefore we’d have to increase the amount of Oxygen as well as the atmospheric pressure and free up most if not all of the water on the planet. Plus we’d have to somehow produce an Ozone layer in the Martian atmosphere. Not to mention that Mars doesn’t have an electromagnetic field anywhere near the strength of ours. So basically there would have to be a whole lot of work done to actually terraform Mars.\n\nThe likelihood that some one country could undertake the process of terraforming an entire planet at this time would be highly unlikely.
634954
Depends on the amount of pollution, The cost of things, house rents, And the friendliness of the people(who knows whether they'll be blood sucking parasites of whether or the next brady bunch), The rate of oxygen masks and tanks... etc.And of course, depends on the space shuttle rates for travelling from mars to earth.
719043
Mars lacks the gravity to hold onto an Oxygen atmosphere for any length of time.\n\nBasically the average speed of the molecules from thermal vibrations is sufficiently high that some of them are moving faster than escape velocity which means that those molecules will escape forever.\n\nA good rule of thumb is that if the average speed is more than about a tenth of the escape velocity the planet won't hold an atmosphere for very long.  There are ways to calculate a half life of a species in an atmosphere but I don't have the information with me at the moment.
831291
The main reason Mars is colder is that it is much father way from the sun. Also the atmosphere is so this, it does not insulated the planet much at all.
1164705
No -- it's a movie.  Suspend your disbelief, sit back, and enjoy a FICTIONAL STORY.\n\nMars is too small to be able to hold on to enough atmosphere to be breathable by creatures that evolved on Earth, with it's relatively thick atmosphere.  The mass of Mars is is one-tenth that of the Earth, and the gravitational acceleration is a little over one-third that of the Earth.  No possible way it could hold on to an oxygen-nitrogen atmosphere breathable by humans.\n\nMass of Earth = ~6x10^24 kilograms\nRadius of the Earth = 6378 km\ngravity on Earth = 980 cm/sec^2\nOxygen content of atmosphere = ~21%\n\nMass of Mars = ~ 0.6x10^24 kilograms\nRadius of Mars = 3397 km\ngravity on Mars = 371 cm/sec^2\nOxygen content of the atmosphere = ~0.13%\n\nMars MIGHT have developed its own forms of life, specifically adapted to the conditions on that planet, but we may not be able to recognize them.