Is water only a liquid?
no, water is a liquid (regular water), solid (ice), and a gas (water vapor).
I would say water, depending on what you're doing. I think they did finally find ice on Mars, but if it's something older, than water may be the answer. LIQUID water. Many planets and/or moons have water, but Earth is the only known planet with liquid water. Actually, we have water naturally occurring in solid, liquid, and gas phase.