I had the fun of judging at a few of these competitions. The recent discovery of evidence of life on Mars in the distant past has brought the subject of life in the Solar System back into the forefront of research and increased our desire to get back to Mars for another look. When we consider the issue of life beyond the Earth, we have to accept that there could be life processes which we have not even dreamt of. For that reason we cannot rule out the existence of life almost anywhere in the universe. There could be living things we might not even recognize as alive.
Life implies the rearrangement of energy, material or information.
Energy has to come from somewhere, be used, and in the process be degraded to another form, usually heat, and then dumped. Imagine you have a lake full of water. Just sitting there it won't make much electricity or do much work. However, if we allow the water to drain out of the lake, down to a lower level, we can use that flow to drive generators to make electricity, or turn water wheels to make flour, crush oil seed, or do many other things. Getting the water back up into the lake for reuse requires at least as much energy as we got out of it.