So, I've been mulling over this idea for a while now and I'm pretty excited to share it with you guys!!! Basically, many people have suggested making ocean planets, with big fish, whales, islands, etc., but in my opinion that's pretty bland - why would you want to visit another planet just to find the same stuff you can find on Earth? Instead, what if you give the whole ocean planet a bit of a twist, and say make it a frozen ocean planet, with abyssal seas plunged in eternal twilight? Ladies and gentlemen, I bring you, EUROPA!
Europa is the smallest of the four Galilean moons orbiting Jupiter - and it's especially interesting because it has the smoothest surface of any solid object in our solar system, which has led to the hypothesis that there may be a saltwater ocean 100 km in depth hidden beneath the sheet of ice that glazes the moon's surface. Scientists agree that if there is extraterrestrial life in our solar system, this little moon is the best chance we have of finding it, and not just primitive bacterial organisms, but full blown complex lifeforms! So, I propose the creation of a planet modelled on Europa, with a thin icy surface and deep dark oceans perfect for exploration and teeming with life.
The planet's surface should be flat and icy, with few variations in terrain save for deep cracks, fissures, and gullies that criss-cross the ice. This land is relatively featureless, with the exception of geyser-like features that periodically spray giant plumes of water from the ocean beneath, together with a few caverns and tunnels that extend deep under the ice. The only real resource at the surface should be salt deposits, which would be an abundant and simple resource that isn't vital but can be handy (like the current organics resource) - the richer resources lie beneath the ice and at the ocean floor. The ice sheet should be thick enough to build a base on, but thin enough to find water if you dig a little too much.
Given the layer of ice blanketing the surface of the planet, the ocean would be extremely dark and life here will be adapted to such a world without sun. The ocean should be divided into two layers; an upper or "twilight" layer, which is dark but not completely pitch black, as a few wavelengths of light do permeate through where the ice is thinner; and a second or "abyssal" layer, which will be entirely pitch black devoid of all light from the sun. The temperature and pressure of these two zones will vary considerably, perhaps even creating a thermocline (a natural barrier where two water bodies of different temperatures meet, but do not mix). The "twilight" zone will mostly consist of the upper water column, the only solid surfaces will be the mangled bottom of the ice sheet floating above, and the peaks of tall sea mounts that rise close towards the surface. The "abyssal" zone consists of the deeper waters and the ocean floor, with hydrothermal vents, deep trenches, and winding submarine cave systems. Resources in these two zones should vary considerably - in my opinion the "twilight" zone would be the easier, more accessible part of the ocean, whilst the "abyssal" zone would require advanced preparation and pose more of a risk, however it would also hide rarer and more valuable resources and artifacts to account for this risk.
Ok, I feel like I need to put a disclaimer here - I'm a marine biologist by profession, and creatures of the abyss is one of my favourite areas, so if I overdo this section I apologise haha! Essentially life here should come in two forms - benthic (on the ocean floor) and neritic (swimming in the water column). Since there is no light from the sun, life here would most likely be extremely bioluminescent, with almost all organisms using light to communicate in some form or other (picture a dark sea full of pulsating neon blues and pinks). I imagine life here would depend on filter feeders, as is common in many gelatinous animals, like sea squirts and sponges, or predators, such as jellyfish and siphonophores. There could also be more complex organisms, ambush predators with massive teeth and glowing lures, gigangtic transparent jellyfish pulsating with light, forests of corals and peacock worms populating the seabed, the works! Going with the two zone idea, I think that the "twilight" zone shouldn't have too many threats, but the "abyssal" zone would be full of potential predators waiting to ambush the player. I'll attach some of my favourite ideas of what you might find below:
Gentle, slow moving, free floating animals:
Sedentary animals fixed to the ground:
More dangerous predatory animals:
(just imagine travelling alongside an undersea cliff, when you hear a clicking sound and all of a sudden one of those worms shoots out of an unseen hole and grabs your sub!!!!!!)
Anyway I have tonnes more ideas for potential alien life for this planet, but that would need to be its own thread hahaha
SUBMERSIBLE:One of the most important aspects of this planet - your submarine exploration vehicle. These would be crafted at a submarine bay, like a vehicle bay but with two arms that creates a hole in the ice and suspends the submarine from the cranes. Personally, I think there should be two types of craft (as was done with the rover and truck, or the shuttle and spaceship). The first will be a small submersible with limited options for upgrades and attachments, restricted oxygen supply (if that is implemented), and is unable to descend into the "abyssal" zone because of extreme pressure - this sub is designed for exploration more than anything else. The second sub will be much bigger, and is capable of taking all kinds of attachments - oxygen tanks, batteries, storage bays, cranes/arms for excavating resources or grabbing artifacts, and a reinforced hull to descend into the abyss. Submarines can be charged at the base, but have significantly greater energy stores and perhaps can be supplemented with emergency fuel reserves to avoid getting stuck underwater and losing your sub. Another point to consider would be defence from threatening animals, and for this I would imagine an electrical discharge that stuns/kills whatever's attacking in a surrounding radius, at the cost of energy. It would also be really awesome if you were able to exit your sub and explore the surroundings whilst tethered, but that might be tricky hard to implement. It would be even more amazing if you could create a base underwater, but again this might be tricky to pull off.
Rare and interesting resources should be abundant underwater, especially in the "abyssal" zone. Many of these resources could be organic in nature, owing to the high diversity of alien life, but there could also be a number of mineral deposits, especially around hydrothermal vents etc. Artifacts should be bioluminescent, and many of them would need to be taken from living creatures - either by plucking off with the sub's arm, finding them on the remains of dead animals, or by killing them directly to gain these special artifacts.
Anyway, that's the idea in a nutshell - there's loads I forgot to mention or couldn't include cos it was already too long!
Tell me what you think