Hrad Vallis is an ancient outflow channel in the Cebrenia quadrangle of Mars, located at 38.7° north latitude and 224.7° west longitude.

[1] Large amounts of water ice are believed to be present under the surface of Mars.

When hot subsurface molten rock comes close to this ice, large amounts of liquid water and mud may be formed.

Hrad Vallis in the Cebrenia quadrangle is close to Elysium Mons, a large volcano, and may have supplied water to create the channel.

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