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Mars, often called the Red Planet, exhibits various geological features that provide clues about its watery past.
Scientists have observed structures such as valley networks, outflow channels, and delta formations on Mars' surface. These features are strikingly similar to those created by rivers and lakes on Earth.
Valley networks, for example, resemble the branching patterns of terrestrial river systems, suggesting that liquid water once flowed through them.
Outflow channels are much larger and appear to have been formed by massive floods, indicative of significant water activity.
Delta formations, where sediment deposits build up at the mouth of a river, further support the idea that standing bodies of water, such as lakes, once existed on Mars.

The mineral composition on Mars gives additional evidence pointing to the presence of liquid water in the past.
Scientists have detected various minerals that typically form in wet conditions. For instance, clays and sulfates found on Mars are significant because they usually develop in the presence of water.
Clays form when volcanic rocks interact with water, altering their structure over long periods. The presence of hydrated salts further corroborates this, as they require liquid water to crystallize.
These minerals suggest that Mars had a more humid environment in the past, which could support liquid water on its surface.

Sedimentary layers on Mars offer some of the most compelling evidence for water activity.
These stratified rock formations are created as sediments are deposited over time, typically in water-rich environments like rivers, lakes, or oceans.
Scientists studying images from Mars rovers and orbiters have identified layers of rock that suggest prolonged interaction with water.
These layered sediments speak to periods when liquid water was present long enough to lay down successive layers of material.
The thickness and continuity of these layers indicate stable and lasting water deposits, strengthening the case for an ancient, water-abundant Mars.