This NASA animation gives us an idea of what the surface of Mars may have been like billions of years ago. When the planet was young, it appears to have had a thick atmosphere that was warm enough to support oceans of liquid water - a critical ingredient for life.
The animation shows how the surface of Mars might have appeared during this ancient clement period, beginning with a flyover of a Martian lake.
The artist's concept is based on evidence that Mars was once very different. Rapidly moving clouds suggest the passage of time, and the shift from a warm and wet to a cold and dry climate is shown as the animation progresses.
The lakes dry up, while the atmosphere gradually transitions from Earthlike blue skies to the dusty pink and tan hues seen on Mars today.
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