At the same time the soil quickly becomes more fertile as it accumulates carbon compounds.

These molecules composed primarily of fused rings of carbon (either neutral or in an ionized state) are said to be the most common class of carbon compound in the galaxy.

Curiosity will search for the third by analysing sediment that could have preserved organic carbon compounds, but progress will be relatively slow.

During photosynthesis, for example, primary producers form organic carbon compounds out of carbon dioxide and inorganic matter.

These reduced carbon compounds can be used as an energy source by the autotroph and provide the energy in food consumed by heterotrophs.