There are already plans about the possibly terraforming Mars. I am wondering which factors are most important in creating a place that is habitable by humans. Also, if there are alternatives to Mars that are currently being considered.
Here is the research that I found about terraforming Mars:
http://www.sciencedirect.com/science/article/pii/S0273117798001665
In my very humble opinion, Mars is not a good candidate because it does not have a sufficient magnetosphere. I don't see any other possibilities in this solar system.
The most fundamental environmental factors while terraforming a planet are temperature and pressure (which drive climate and weather), global energy balance, cryospheric-hydrological content and cycles, biogeochemical cycles and atmospheric composition. The ecology of a planet is then derived from these environmental conditions, as each species works together to adapt and evolve in their environment. We have only scratched the surface of potential planetary pathways.
Apart from Mars, the most viable planet (or moon) for terraforming would be 1) the Earth's moon, 2) Titan, 3) Venus, 4) Ganymede, and many other potential possibilities, depending all on assumed technological abilities (see my project link below).
I have also attached great publications in helping you answer your question. You may also refer to the 73 references listed on my project page:
https://www.researchgate.net/project/Terraforming-of-Terrestrial-Earth-sized-Planetary-Bodies
Article Biology and The Future of Mars
Article PLANETARY BIOLOGY AND TERRAFORMING
Chapter Terraforming Mars: A Review of Concepts
As Peter mentions you need a planet / moon that has a significant and stable magnetosphere. It doesn't matter what you do to create an atmosphere if it is quickly eroded away by the solar wind. So I think that should be the most important consideration for any terraforming.
Phil J Sutton,
I too agree that magnetospheres are required to retain an atmosphere of a planet or moon, however, it really is just a game of input – output. If you're adding atmosphere to a planet in hopes of terraforming it, all you would need to reach steady state is for the rate of atmospheric gain to equal the rate of atmospheric loss from solar wind. Then any further atmosphere you contribute to the planet will be a positive gain.
In the case of Mars for example, we know the atmosphere is decreasing at a rate of –x, then the rate of atmospheric gain you would need to add to Mars to terraform it (+T) would be x + T, solving from steady state where the martian atmosphere remains constant in pressure would be: dx/dt = x – x = 0. And finally, solving for the rate of atmospheric change with terraforming is: dx/dt = x – x + T = T.
To update my answers to this question, nearly all terrestrial planets and moons in our solar system are suitable for planetary engineering, given ample technology and resources. Ultimately the explorative drive of humans and the necessity to become a multi-planet species will determine if and when we do this.
Ultimately, I think the best six candidates for terraforming go as follows:
Of course, all of these present their own unique challenges, such as distance from the Earth (getting there), and gravitational atmospheric retention.
See my recent research on Terraforming here:
Technical Report Terraforming of Terrestrial Earth-Sized Planetary Bodies
Article Planetary engineering theory and its application to future t...