The planet Mars seems to be a mystery that can never be solved! Recent research has found that there needs to be an underground source of heat on Mars for liquid water to exist underneath the planets polar ice cap, and that heat might be sourced from an underground volcano!
The new research does not take sides as to whether the liquid water exists. Instead, the authors suggest recent magmatic activity -- the formation of a magma chamber within the past few hundred thousand years -- must have occurred underneath the surface of Mars for there to be enough heat to produce liquid water underneath the kilometer-and-a-half thick ice cap. On the flip side, the study's authors argue that if there was not recent magmatic activity underneath the surface of Mars, then there is not likely liquid water underneath the ice cap.
Image Credit: NASA