Where is all the water that once flowed on Mars? Select all that apply. A. underground B. in polar ice caps C. evaporated into space D. Water never flowed on Mars.

Water on Mars exists today almost entirely as ice, though it also exists in small quantities as vapor in the atmosphere and occasionally as low-volume liquid brines in shallow Martian soil. The only place where water ice is visible at the surface is at the north polar ice cap.