Were there ever oceans on Mars? This computer-generated image shows how Mars might look with oceans. The climate of Mars, like Earth's climate, changes over time. Variations in the tilt of the planet's axis and to its orbit have created warmer climates at times, and ice ages at others. Some scientists think Mars may have had oceans during warmer, wetter periods in the planet's past. Such seas would mostly appear in the northern hemisphere, which has a much lower elevation than the southern highlands. If the northern plains were once covered by an ocean, they seem a great place to search for remnants of water and signs of Martian life, past or present. In this view the volcano Elysium Mons forms a large island towards the left side of the image, while another volcano, Olympus Mons, lies along the eastern shore of the ocean (right side of image).
Image courtesy of NASA/Goddard Space Flight Center Scientific Visualization Studio.