Life support systems allow you to move around the planet. Sprinting (L Shift) and using the Jetpack (Space) will drain life support power.
Life support systems are recharged with Oxygen. Pressing [Key C] will activate the Scanner, locating nearby Oxygen-rich Plants. Oxygen is found on all worlds.
Systems can be recharged from the Exosuit inventory, or via the Quick Menu using (Key X).
Other ways to refuel life support include Life Support Gel, crafted from Di-hydrogen, and Oxygen Capsules crafted from Carbon and Oxygen.
Analysing plants with the Analysis Visor reveals their bonus materials, which often includes Oxygen. Harvest these materials with the Mining Beam.