The MegaCredit (M€) is the general currency used for buying and playing cards and using standard projects, milestones, and awards.
Steel represents building material on Mars. Usually this means some kind of magnesium alloy. Steel is used to pay for building cards, being worth 2 M€ per steel.
Titanium represents resources in space or for the space industry. Titanium is used to pay for space cards, being worth 3 M€ per titanium.
Plants use photosynthesis. As an action, 8 plant
resources can be converted into a greenery tile that
you place on the board. This increases the oxygen
level (and your TR) 1 step. Each greenery is worth 1
VP and generates 1 VP for each adjacent city tile (see
map rules on page 5).
Energy is used by many cities and industries. This usage may either be via an action on a blue card, or via a decrease in energy production. Leftover energy is converted into heat
Heat warms up the Martian atmosphere. As an action, 8 heat resources may be spent to increase temperature (and therefore your TR) 1 step.
Other resources (including animals and microbes) are
collected on their respective cards which also define
what they do.