The caldera on the summit of Olympus Mons is surrounded by lava flows. This giant volcano is the largest and tallest in the solar system, at 15 miles (24 km) high.
Mars has long been thought of as a possible haven for life. We now know liquid water, an essential ingredient for life, played a major part in Mars's past. Space probes have looked for signs of life on the Martian surface, and a Martian meteorite on Earth was once thought to contain fossils of living organisms. In 2004, the rovers Spirit and Opportunity began searching for clues to what Mars was like when liquid water was present.
Opportunity has found hematite-rich pebbles on Mars. Hematite is an iron-rich mineral, which on Earth almost always forms in the presence of liquid water.
phobos and deimos
Two small moons orbit Mars. The bigger of the two, Phobos, is 16.6 miles (26.8 km) long and orbits 5,830 miles (9,380 km) from Mars. Deimos is just 9.3 miles (15 km) long and two-and-a-half times farther away. These dark, rocky bodies are believed to be asteroids captured by young Mars's gravity.
Mars rotates every 24 hours 37 minutes
Deimos completes a quarter of its orbit in the time it takes Phobos to orbit Mars
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