Why is water sequestered deep underground on Mars, unlike on Earth where it cycles through surface processes?

Answer

Plate tectonics does not cycle water back to the surface.

The deep water is sealed off by an overlying cryosphere. Unlike Earth, Mars lacks plate tectonics to cycle this deep water back to the surface, resulting in long-term geological sequestration.

Why is water sequestered deep underground on Mars, unlike on Earth where it cycles through surface processes?
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