Greenhouse effect on Mars and Venus?
It's not just the composition of the atmosphere - it's the *quantity* of atmosphere. Venus' atmospheric pressure at it's surface is 90 times that of Earth. Standing on the surface of Venus is like being 3000 feet under the ocean here on Earth - that means it's a *very* thick atmosphere, with trillions of tons more of CO2 than what exists on Mars.
Why is there little greenhouse effect on Mars today?
Because the Martian atmosphere is already more than 95% Carbon Dioxide, and extremely thin. EDIT: Please read my link Cosmic.
If we removed greenhouse gases from Mars, how hot would it be?
You can estimate the greenhouse warming effect on Mars by knowing the difference between its effective black-body temperature (which is the average temperature of the planet if it were heated only by solar radiation) and its average temperature. The effective black-body temperature of Mars is estimated to be 209.8°K (Source: NASA Mars Fact Sheet) while its average temperature is estimated to be~ 210°K (Source: NASA Mars Fact Sheet). Therefore the greenhouse effect on Mars (almost exclusively from CO2) is responsible for increasing its temperature by a paltry 0.2°K.
Is it possible to build a greenhouse on Mars using the technology we have today that could sustain a few stranded astronauts indefinitely?
There are three thoughts that come to mind:1. Matt Damon apparently alternates playing roles of astronaut jackass and astronaut badass. This suggests that his next movie after the Martian will be playing the lead role of a serial killer in outer space. 2. Survival on Mars is only possible if we melt the ice core and make a new atmosphere. The ancients figured this out but the mean spirited corporation has been selling oxygen at high prices instead. 3. The real answer to your question is not by any damn stretch of the imagination. A self sustaining Martian colony is an unbelievably difficult task with about a million hurdles and a $20 trillion price tag (probably more). Since Mars has temperatures and gas mixtures that are inhospitable to human life and does not have surface water, the best way to have a Martian colony is probably to build biodomes. Terraforming Mars (ie changing it to be like earth) is probably so hard that it's unlikely that anything humans could develop in the next 10k years could do it. But building a biodome, with enough technical advancement and enough investment of money, could possibly be done in the next 100 years. No astronaut could just "science the shit out it" in real time. All of this is predicated upon will. Humans had a huge zeal for space in the 1960's. That zeal was nearly completely lost in the 1980's. With the advent of space travel privatization and space tourism, the interest seems to be on the upswing. Money and need will ultimately drive it. If we had an unequivocal message from the gods that earth would be uninhabitable by 2350, then we might see crazy work being done on this. Or maybe people would ignore said message until the affected generation was born. Regardless, it is well within our reach to build a self sustaining Mars colony in the next couple hundred years (hell, probably sooner). It just takes diverting a lot of money and resources from building air conditioned soccer stadiums in 120 degree countries and massive hotel fountains in the middle of the American desert and putting said resources into space. I don't see that as being politically viable now.
Is it possible to "inject" oxygen into the atmosphere of say, Titan or Mars to induce life?
Oxygen was put into the Earth's atmosphere by Cyanobacteria, which were the first forms of life. Scientists believed that these bacteria formed in water. If these bacteria put Oxygen into the atmosphere, then they must have survived without it in the first place. Perhaps extremophiles could live on Mars?!? Mars does have water at its poles, but there would not be enough there to sustain human life long-term. The water arrived on Earth during the late heavy bombardment, when comets hit the Earth providing water and forming oceans. Scientists and recent evidence suggest that water used to exist in abundance on Mars, as there are what appear to be ancient water flows that have eroded the surface. However, this water is thought to have evaporated and disappeared into space. Mar's atmosphere is disappearing into space, and as such, it only has a very thin layer of atmosphere. This is my contribution to this question, i would like to see more on this! Kind regards Leanne
Increasing atmospheric pressure on Mars?
The polar caps of Mars are mostly made out of dry ice (solid CO2). By increasing their temperature by just a few degrees, we can make the solid CO2 into gas CO2. Then the gas will cause a greenhouse effect therefore warming the planet and causing the the ice beneath the surface to melt out. This will cause Mars to have nearly 100% the atmospheric pressure of Earth, have a suitable temperature for life, and have lakes and oceans. Plants will easily be able to survive there however the atmosphere will not have oxygen so we have to come up with a way to turn CO2 into O2 because it will take thousands of years of plants to do that for us. How can raise the temperature of the caps in the first place? 1. we can send giant mirrors to reflect sunlight to the caps which will raise the temperature by at least 50 degrees Celsius. 2. we can heat them with nuclear rectors. 3. We can make green house gas producing factories on mars. Before we can do this, we have to find a new way to get to mars because rockets aren't efficient. However look at how much technology has improved over the past century. I am sure we will overcome the challenges in the next few centuries. Here is a documentary you might like which associated with your question (the mars underground): http://www.youtube.com/watch?v=M3REZZWeW... Here is a book coming out in a few months that you might like: http://www.amazon.com/How-Live-Mars-Guid...
Why do people think terraforming Mars is doable when we know NASA says there's not enough CO2 on Mars to create greenhouse effects and allow liquid water?
The answer completely depends on what terraforming means. Let’s take the minimal approach. You can walk on the surface with warm clothes and a respirator. That would take something upward of 500 million tons of gas. You’d like to chuck the respirator? That would require around 770 million tons of gas added to the atmosphere. My calculations suggest that 670 million tons of O2 along with around 100 million tons of an inert gas would make the planet almost breathable. You’d have to remove some of the CO2 and essentially all of the CO to get there.NOTE WELL: We are removing and not adding CO2!! Would you like to breathe that air?According to NASA calculations, you’d have to have somewhere close to 1 atm of CO2 to warm the planet enough to keep water liquid. Warmth is not terraforming in my book. Breathing is. You can grow your crops in greenhouse domes, doubly insulated ones with some extra radiation protection. UV will be taken care of by the ozone layer which will not exist on Musk’s planet with all of its CO2 and no O2.We can live in Siberia. If we can build up a breathable atmosphere on Mars, we can live there too. Sure, we can live in shelters without that, but it wouldn’t be terraformed by anyone’s definition.