Possibilities for civilization and spacefaring capability on other worlds

The view from a hypothetical planet orbiting Alpha Centauri A. The second sun in the sky may be a good source of PR for the exploration of space for any civilization existing there.

Thanks to Kepler, COROT and observatories on the ground, within about a year or so we should have begun to discover the first Earth-like planets. Earth-like doesn't necessarily mean that a planet would be just like our own; Venus is technically Earth-like and seen from afar others might assume it to be a much cooler planet than it really is, so just discovering these planets doesn't necessarily mean we've discovered life.

However, the number of planets is nearly without limit, and there are many ways in which life could exist: underneath the surface of an icy planet where a liquid ocean can exist is one example. Also don't forget that life could exist where Jupiter-sized planets in habitable zones are located...because these planets often have large moons orbiting them, and moon located within this area would be within a star's habitable zone as well.

After determining the possibility for life though, the next question is whether there is intelligent life, and if so whether there is civilization, and after that whether this civilization has achieved the ability to go into space. Eventually the number of Earth-like planets we know about will reach into the thousands and focused observation may have to be limited to those that have the highest potential for intelligent, hopefully spacefaring life.

So, what types of planets have the best opportunities for spacefaring civilization? Let's think about that a moment.

First, in order to get into space you need two things: 1) the desire to get into space, and 2) the ability to do so. It probably stands to reason that the more interesting a solar system one lives in the more an intelligent civilization would want to eventually explore it. We have always had the Moon up in the sky to watch and wonder about. Mars has two moons that are much smaller, and much closer, and some planets have none. It's probably likely that the more moons a planet has that can be seen from below the more people on the ground will have an interest in the sky, as this is a 24/7 source of PR for space.

On the other hand, you could also make the argument that having the Moon in the sky has turned us on to the idea of exploration too soon, and that we've spent too much effort trying to get out into space and not enough time just trying to understand it. If there was no Moon in the sky and we were very well aware that there was no possibility of getting people to other planets any time soon, would we have invested the same funds into observation instead? If that were the case we might have discovered other Earth-like planets and changed our view of space a few decades before now, instead of it being 2009 or 2010 before we found any.

One aspect of a planet that doesn't seem to be up for debate though is mass. Having a less massive planet seems to be an advantage in becoming a spacefaring civilization. A planet of our mass has an escape velocity of over 11 km per second, whereas one like Mars is less than half that. In other words, if we had been a civilization based on a planet of that size it would have been that much easier to get into space in the first place, and the cost to do so would have been much less than now. In addition, a place like Titan with a low gravity and especially thick atmosphere would have had flight since ancient times, since flight would require little more than a stiff pair of wings to flap. Imagine a civilization with flight right from the very beginning of the bronze age, instead of having to wait until the modern age as we did. For a civilization like this it would be very easy to make the progression to space.

At the same time, having a moon in just the right place can help matters even more. I wrote a few days ago on how having our Moon seems to be a bit of a curse since thanks to having it nearby we can't seem to decide on where to make the most effort - going to the Moon first, or Mars, or LEO...but a Moon in just the right place (maybe 50,000 km away) could be both an incentive to go to space, as well as an obvious first destination for colonization.

Another good factor would be the presence of another star system nearby. Alpha Centauri for example has both A and B, as well as Proxima Centauri, which is a far more interesting configuration than our own Solar System with only a single star. The two main stars in the system can get as close to each other as Saturn is from the Sun, and as far out as Pluto, distances that we have already easily surpassed. IOW, in that system there's just more to see and do than ours.

So a bit of preliminary thought would seem to suggest that planets less massive than ours, with a well-placed moon, and with other stars or interesting objects nearby would be perfect places for a spacefaring civilization to develop, and perhaps we should spend most of our time checking out these places after we have found a great many Earth-like planets.

One other issue to take note of though: what about maturity of a civilization? It may have been a good thing for us that we didn't achieve the ability to reach space before we did, as imagine a simple feudal dictatorship with that sort of capacity as opposed to a functioning democracy with limits on governmental power. If life on other planets is as violent as it is here on Earth (and that's not a given either), perhaps it's actually better for life to exist on a planet where it's difficult to achieve things like flight and the ability to go to space, as that would be giving an emotionally young civilization much too powerful tools for it to responsibly handle.

Since our total sample size for civilization is a grand total of one though, this is all just speculation. In any case, my hunch is that planets less massive than the Earth with lots of interesting places in the neighborhood to explore are the best places to keep an eye on the most. Your thoughts?