Heat, or more specifically, temperature is a relative parameter of life.
We like things around 20C. Organisms living around hot springs like it at 100C. Organisms around the deep oceanic black smokers are happy at 150C. Algal life has been found thriving hundreds of metres inside the Antarctic iceshelf. Not much heat there and certainly no light.
The fact is, life occupies every nook and cranny of the Earth, provided there is water. Whatever else these things need, they seem to find it. If there's water on Mars, life would not only be possible, but probable.
Cheers,
JaX
