Formed?
Tons of ice pellets hit the Earth every second, every day, and probably have since time began.
If they pelt the Earth, they pelt every astronomical body in space.
Formed as in how the water (not the ice) that is being dispelled in the geysers formed, as in did it form in the cracks in the surface or is there a larger deposit of liquid water under the surface that eventually makes it to the surface where it is expelled.
That still doesn't answer the question of where the water the ice pellets consists of came from or how it came into being. Mainly, how.