> by definition some source of energy is warming it over zero Celsius degrees. And if there are huge oceans of liquid water, the source of energy somewhere must

> by definition some source of energy is warming it over zero Celsius degrees. And if there are huge oceans of liquid water, the source of energy somewhere must be huge also. This is all that life needs to thrive. Unless you're counting the warmth itself as the energy source warming it, I don't think this has to be true. Earth's core is hot mostly from residual heat from the Earths formation. It's cooling. It just takes a long time. Thermodynamics won't let you extract useable energy from the ambient temperature. Lifeforms could extract energy from a strong temperature gradient, but not from something like 1°C per kilometer. The energy source for deep ocean life on Earth is life from near the ocean's surface that dies and falls down. The study in the article was investigating if something similar could happen on Titan due to surface impacts.