There I was watching TV when someone quipped that there might be life out there surviving by chemical energy. What is chemical energy? Is there already in existence life surviving by chemical energy?

Chemical energy is just energy stored in chemicals. Most earthly life runs on the chemical energy stored by green plants in the relatively complex chemical chlorophyll, and/or on energy (again, stored chemically) in other forms that can be traced back to chlorophyll). Some earthly life runs on the energy stored in chemicals coming from hot deep sea vents in the simple chemical hydrogen sulfide (H₂S) or on energy (stored chemically) that can be traced back to H₂S.

Methos, as usual, has explained things quite well. Here's a different side of it:

Chemical energy is stored in the chemical bonds that hold atoms together into molecules. It's a form of electromagnetism, and it all boils down to how the negatively charged electrons interact with the positively charged nuclei in their vicinity, as well as each other, subject to the constraints of quantum dynamics.

The repulsion of like charges -- and attraction of unlike charges -- within molecules are like little springs or rubber bands, able to store potential energy (like compressing a spring or stretching a rubber band) and release it later when the molecule reacts (Sproing! Snap!). A moustrap makes a nice analogy.

In a chemical such as dynamite, the chemical energy is very high per molecule (the bonds have *very* tight "springs") and chemical energy is released quickly in the form of heat and motion.

In living organisms the organic molecules release their chemical energy more gently, and in a much more controlled fashion due to the complexity of biochemistry. But the principles are the same.

Many biological systems use chemical energy stored in ATP (adenosine tri-phosphate) molecules, the "common currency" of cell processes.

So the original comment about life "out there surviving by chemical energy" is not terribly shocking. Energy such as starlight impinging on molecules can be stored within the molecules, thus converting radiation energy into chemical energy.

Excuse me now, but the doorbell just rang. It's time to replenish my chemical energy in the form of a pepperoni pizza.

Jumping off Professor's post, all life on Earth uses ATP to store energy, so one plan to look for signs of life on Mars is to look for ATP, but the tests will have to be adapted to work in Mars' harsh climate.

We have observed the spectroscopic 'fingerprints' of some carbon-based chemicals in space, so their is definitely chemical energy stored out there, but we don't have evidence of any life forms putting it to use. I don't think what we've found could sustain life as we know it, but we're not looking for life as we know it floating out in space

The TV show I was watching mentioned that new life forms are quite strongly growing in some unexpected places, but I admit that I half slept through the show. I can relate better to veggie pizza.

There is no credible evidence for any kind of life beyond Earth.

Certainly "extremophile" organisms turn up in unexpected places on Earth. And organic molecules are widespread in space. And in the vastness of the universe, extraterrestrial life is plausible and maybe even likely. But so far evidence is lacking.

The discovery of even the humblest microbes living outside our planet would make unforgettable headlines and forever change humanity's view of itself. Nobody would sleep through it!

The TV show said what you just wrote, but I did not catch the "e" word from it.