What is the Ecodome?
The ecodome is an enclosed area on the surface of Mars. This is where the astronauts and all the other plants and animals you bring with you will be living while they are on Mars. It is important to have an enclosed area because conditions on the surface of Mars are very different from those on the surface of Earth. People couldn't live on the surface of Mars without protection from the harsh conditions there, and crops couldn't grow on the surface of Mars.
Mars is much colder than Earth, with low temperatures as low as -120 degrees C. It can also get up to around 40 degrees C. in certain places at certain times. The ecodome can be heated with solar panels so that temperatures are right for things brought from Earth. This also allows the water that you have mined on Mars to stay in liquid form instead of instantly freezing as it would on Mars if the dome wasn't there.
Mars' atmosphere is naturally very thin and made almost entirely of carbon dioxide. The ecodome will be filled with an atmosphere that is like Earth's atmosphere, containing mostly nitrogen, some oxygen and a little carbon dioxide and water vapor, as well as other gasses. This is an atmosphere that can support living things from Earth. All plants need carbon dioxide, and all animals, herbivores, omnivores and carnivores alike need oxygen.
You must choose how large the ecodome is. Do you want a very large area to fill with plants and animals, or do you want a small one?