‘Photo’ means light and ‘synthesis’ means putting together. Hence, as the name suggests, photosynthesis is putting together the light energy with molecules of carbon dioxide and water to permanently store the energy in the form of carbohydrates or sugars. These carbohydrates are stored in plants that can be accessed by animals, insects, and every other fauna.

Note that, the organic molecule (containing ‘Carbon’ atom) and solvent in the case of Earth is ‘Carbon dioxide’ and ‘Water’. In the case of Venus, it could be ‘Carbon dioxide’ and ‘liquid Methane’. What matters is a Carbon compound and a solvent.

We have learned this in school. But have you heard about Chemosynthesis? Let’s try to break down the word and understand.

‘Chemo’ means chemical and ‘synthesis’ as discussed above is putting together. So its clear difference with photosynthesis is that, instead of light energy, spontaneous chemical reactions with inorganic molecules (those not containing ‘Carbon’ atoms) to generate heat energy which then reacts with carbon dioxide to form carbohydrates.

Organisms using these processes to generate energy are mostly bacterias and tapeworms. These are found mostly in areas with an abundance of inorganic molecules and some heat energy. Like, underwater volcanoes or any form of Earth’s thermal energy.

Again, like before, the inorganic and organic molecules in these cases could be variable. For Earth consider, Hydrogen Sulphide and Carbon dioxide.

To conclude, the end products in both these cases are carbohydrates but the forms of energy are different, light and inorganic reactions. This suggests that light is not necessary for any living form to survive.

Therefore, underground layers of Mars or any of Jupiter’s moon can also harbor chemo-synthetic lifeforms living on the planet’s thermal energies or their moons tidal forces.