Evidence of water on Mars from Mars Odyssey

Previous studies with infrared spectroscopes have provided evidence of small amounts of chemically or physically bound water.

When the measurements were gathered, it was winter at the north pole so carbon dioxide had frozen on top of the water ice.

[11] Thousands of images returned from Odyssey support the idea that Mars once had great amounts of water flowing across its surface.

Lineated floor deposits may be related to Lobate debris aprons, which have been proven to contain large amounts of ice by orbiting radar.

Dao Vallis begins near a large volcano, called Hadriaca Patera, so it is thought to have received water when hot magma melted huge amounts of ice in the frozen ground.

The partially circular depressions on the left side of the channel in the image above suggests that groundwater sapping also contributed water.

[20] In some areas large river valleys begin with a landscape feature called "Chaos" or Chaotic Terrain."