OK, so my characters are going through a wormhole to colonize a habitable planet on the other side. They'd have sent probes through first, which found an earthlike, habitable planet in a solar system. So, my questions are, first, what level of information would be needed to tell that a planet is definitely going to be habitable? And secondly, what would be some interesting quirks that this planet could have (eg two moons, weird axial rotation, etc) and how might they affect life on the planet's surface?
Well the obvious ones are climate, gravity, and atmospheric composition. If they can't breathe or stand on the surface they wouldn't last very long. Those could reasonably be ascertained by a "probe." Then you would need a food and water source, which would be loaded with alien bacteria, contagions, viruses, etc. Axial tilt affects the seasons and the amount of day light/night. Tilted enough, as with Mercury, you would have perpetual zones of day and night where the sun never sets/rises. That would obviously play hell with life and photosynthesis and all that jazz. Multiple moons, depending on their mass and orbital distance would play hell with the tides. Really, the quirks are endless are purely speculative. We have exactly one case study of a habitable planet (Earth) so nobody really has a clue what the others would look like. There's been plenty of theoretical models and research, but nobody knows for sure. @newjerseyrunner would probably be the cat to talk to about this.
You'd need to know the temperature and composition of the atmosphere. That may require visiting it, but if we're lucky, we can figure all of that out remotely with spectroscopy. In the current world order, scientists have taken the universal stance that if it's already got life on it, or even could have life, we leave it alone. For example, The Cassini spacecraft orbiting Saturn is running low on fuel so they're going to divebomb it into the planet instead of risking contaminating one of the moons. There would have to be increasing social pressure to get the scientific community to abandon this, but lets assume that your planet has life. The axial tilt will affect evolution, and would have to be fairly stable in order to nurture a biosphere. This requires a large moon. Most planets swing around wildly, but Earth stays put because of the stabilizing affect of the moon. If you have multiple moons, you'd either have to have one big one and one little one or two small ones or else the system would be unstable. Small moons will have almost no affect on tides. Our moon is actually pretty huge. The biggest thing to get over would be chemistry. Our cells have very powerful defenses, so alien bacteria could not thrive in us, but the fact that our immune system will destroy them may cause its own problems. You don't know what chemicals the local life uses in order to work and if it releases the wrong one, it could seriously affect humans. Think of how little THC it takes to completely change how you think.
Far out, man. I'd volunteer for the mission to the THC planet . Got me a PhD and some research skills to offer the community.
Oh, they'll study the hell out of it. They'll just be extra careful not to cross contaminate. They'll do things like when a probe is running low on fuel, they'll steer it into the star or a sterile moon. A necessity of observing is to interact as little as possible. For most life, that simply means that we don't want to accidentally release something that'll displace the life that currently exists there. If it's intelligent life, we'd want to study their culture without altering it, and we all know that when one culture encounters another, the less advanced tends to be obliterated and scientists will avoid that at all cost. Imagine how human civilization would be different if we discovered that there was something far more powerful than us watching over us (which is entirely possible.)
I'd like to come to colonize this planet. I have no education, but I'm a military veteran, so you know I follow orders unquestioningly, and I'm a fearless zealot with no regard for my life or safety. Loose nozzle outside, and our suits are all damaged? I'll walk out there to tighten it, for the good of the colony. Suffer not the colony to fail.
They would most likely do atmospheric scoops, searching for acceptable gases in the air so that it could support basic humans. (Oxygen, nitrogen, carbon dioxide, and so forth like we have here on Earth.) Water in a liquid state, so as to suggest that the temperature is within a tolerable range, and can be used since it is a very important molecule that makes up 70-75% of the human body. As for the question of life being there, well that all depends. Our species has a rather negative track record when it comes to discovering indigenous populations of our own kind in our own history. So it all falls upon whether they are intelligent enough, and how we react to the new beings. They could see us as an invading force, and try to kill us. We could see them as something to conquer and all that lovely jazz. Perhaps we get along with the natives, and work together in harmony. If it is filled with animals and nothing of higher intelligence to match/exceed ours, we might use them for work/pets/food. Whatever life may exist in either carbon or silicon form, you can bet that their is a whole new vastly different microbial life that we are not familiar or immune to. Which means having an advanced medical/biological team on hand to help keep people from simply getting sick and dying from viruses/diseases that will need to be addressed and hopefully cured/vaccinated against. There is the possibility of finding a tidally locked planet in the habitable zone, and there is a ring around the plant surface that can support life, leaving the majority of the surface too hot/cold to be inhabited. But all you really need is a plentiful amount of water (solid or liquid), and a way to find/farm food for a colony to be self sustaining. Also pack an envirosuit with plenty of armor and radiation protection, just incase you can't walk outside your habitat and breath the air.
One of the biggest things that's going to affect (human) life on the surface of the planet isn't even that much of a quirk: How long is the day/night cycle? People can get really screwed up when the circadian rhythms don't line up well with the coming and going of the light. I'd suggest doing a quick google of "non-24". As far as quirks go, there are a lot of potential quirks that would make the planet less than habitable, and relatively few that maintain habitability. You probably want your planet to have a large moon if complex life naturally developed on it; any other moons should be small relative to the size of the planet and major moon. Or, here's an idea, have it be a double-planet. (Which is to say, the moon is so large relative to the planet that the center of mass around which they orbit is well outside of the planet. The two planets would likely be tidally locked, so that they always show each other the same face. In our solar system, Pluto and Charon have such a relationship.) Other than that, your best bet might be the night sky. Perhaps this planet's system is far away from the plane of the galaxy, so that there are few stars in the sky and instead of a milky band across the sky, there's a great disk visible. Or maybe the planet's star is in a nebula, so that there's always 'clouds' partially obscuring the stars. Or there could be a nearby variable star which oscillates between looking like a normal star and being brighter than our full moon.
The problem with a tidally locked double planet is that the gravity dynamics cause the cores and heavy materials to shift to the side facing the other object. This would cause it to solidify quickly, killing any Tectonic activity and trapping all that energy inside. That'll produce wicked volcanos which will spew lots of carbon dioxide. It'll also cause the core to spin much slower, which will remove the magnetosphere which will be required to protect surface life.
How about have it be on a moon of a larger gas giant, the planet being 3 times the size of our earth or maybe there's even 3 moons close together of this gas giant all habitable and all have different colonies on them...? Could be cool. So they'd be planets bigger than earth by a coupl e earths, but be moons of a gas giant with multi rings around it.
Oh and then if you have like 3 different moon planets...you could have them connected together by a giant space elevator between all 3 worlds with a space station in between. =) controlling everything - maybe a space station in the middle holds the space elevators in place and allows for rapid transit between the two - and for interstellar craft docking and taking off. and the station could be neutral llike DS9 or maybe controlled by whichever planet government is in control at the time. Maybe the two planets are peacful and more concerned about neighbors but maybe they are at war and your probe uncovers this.. and gets your explorers involved in the war unintentionally.
They couldn't be physically connected, distance between moons changes constantly as they move in their orbits. Three might be hard to explain physically. You'd probably have to make them pretty far away from the planet for a number of reasons. Large planets tend to have deadly radiation zones, which no life could thrive in. Three large moons would also be difficult to stabilize. They'd have to be in some orbital resonance (probably 1:1, 2:1, 4:1.) The inner one would experience pretty wicked tidal forces and likely be a volcano world.
I went through this same conundrum when I wrote my first novel, Cast Into New Eden. (I'm currently polishing-off the sequel.) I decided early-on that too much coping with a hostile, truly alien environment would just drag focus away from the main story and message. That said, I gave the planet a moon, similar day/night times to Earth, a similar period of rotation around the sun, and a compatible biochemistry. There are concerns for unknown bacteria by the residents, and there is a population of indigenous fauna (as well as flora) which is different in detail to Earth's. I basically "made" the planet about 50,000 years younger than Earth, threw in some things I learnt in biochemistry and compensated for New Eden's heavier gravity. I like to think I added a distinctive color to the planet, whilst not posing problems that I saw as insurmountable to colonists from Earth. For the people and their characteristics, attitudes, thought processes, social mores, etc, I drew on my experiences as a scientist, because that was an important part of the story. To me, the setting is just that, and it needs to be convincing enough for the reader to suspend disbelief, so I put a degree of effort into it commensurate with its importance. If I go to the theatre, - Jersey Boys springs to mind as an example that I truly enjoyed - I didn't storm out yelling about how the prop on stage wasn't a real car. It is possible I guess, to devise unique biochemistries and build from there, but I can't see how that adds to the story or message. And if a writer chooses to go that route, then I think it needs to be utterly perfect and a core element of the story. I recall one story where the writer substituted sulphur for oxygen in the biochemistry of all creatures and to me it immediately seemed so impossible, let alone probable that it stayed with me for some 40 years. I can't recall what the story was about, but I remember that.
