The most interesting and provocative querie concerns the settlement and possible terraforming of Mars. We have to put starships out of our minds for now, because it seems we have at this time no way to communicate with ships that escape the solar system. There is a peculiar phenomenon just outside the reaches of the solar system and it is comprised of an unusually dense cloud of gas and dust particles called the Oort Cloud. Both Voyager and Pioneer are lost in or beyond this cloud. All contact is impossible because at this distance the sun doesn't generate enough energy to power solar cells, and I'm not sure if nuclear batteries can generate enough power for that long for us to be receiving any communication from that far away. Even stars only give us a small amount of information, the nearest one is only a pinpoint of light and a spacecraft's communication module is embarrasingly insignificant by comparison.
But there are possibilities for Mars. We know that oil is the waste product of the digestion of the ferrite substrata in the Earth's mantle by a bacterial fungal mold in that oxygen-free environment, in an anaerobic process. It's been happening for billions of years and continues to happen and is probably representative of the very first life cycle to evolve on this planet, long before oxygen occurred in the atmosphere, and there is no reason to believe that it couldn't be happening in the iron-rich mantle of Mars, especially if, as I believe, that the fungal mold spores that caused this natural miracle arrived here freely floating in from space. I really believe that there is a high probability that oil exists in Mars as well and that would be a great boon for future Mars settlements because almost everything can be made from oil, from building materials to fuel to whipped dessert topping.
No doubt many here have seen the series
Starhunter on TV. It is one of the most realistic future scenarios ever devised for television because the premise of the show is based on the acknowledgement that interstellar travel is pretty much science fiction without some new kind of science to make it possible, such as hyper-space travel, which no-one from our solar system had yet mastered. The show was not without its interesting concepts, for there is indeed a lot of exploration and discovery to be done in our own solar system, planets and moons to inhabit and conquer, space colonies to orbit the giant gas balls etc. etc. not to mention the extraplanetary politics and sociology. There is yet so much to be done that I am not the least disturbed by the idea of turning our backs on interstellar exploration.
For further information on the subject of realistic and "practical" intra- and inter-stellar space travel you would do well to pick up a copy of the book
Entering Space, by
Robert Zubrin, former senior engineer at Lockheed Martin, founder of Pioneer Astronautics, and founder of
The Mars Society. There is even a modicum of math, concerning the calculations for the fuel load requirements for various hypothetical space journeys.