Where is the vast majority of Martian water currently locked away?

Answer

As ice in polar caps and beneath mid-to-high latitude soil.

The largest existing reservoir of Martian water is in solid form, concentrated in the polar ice caps (a mix of water ice and frozen carbon dioxide) and as extensive sheets buried beneath the surface soil in the mid-to-high latitudes.

Where is the vast majority of Martian water currently locked away?

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