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Planets and moons

The story of Mars

Victoria Crater on MarsVictoria Crater on MarsMars, along with the other terrestrial planets, began to form 4.6–4.5 million years ago. For millions of years afterwards, Mars was pelted with comets, asteroids and meteorites. Evidence of these impacts remains to this day as thousands of craters scattered across the Martian surface. Volcanic eruptions occurred in the Tharsis region, where an enormous mass of volcanic rock, known today as the Tharsis Bulge, gradually built up. Vast quantities of gases were released from beneath Mars's crust, forming its atmosphere. This was much denser than it is today, making the climate warm enough to allow rain to fall. Large lakes and rivers formed in Mars's southern hemisphere, and an ocean may have covered the low-lying northern plains.


Mars, a watery planet during the Noachian PeriodMars, a watery planet during the Noachian Period

A watery world

The oldest terrain on Mars is found in what is called the Noachis Terra (the "Land of Noah") region of the planet's southern highlands. The region has given its name to the Noachian Period, a span of time lasting 4.3 to 3.5 billion years ago, when Mars was, at least for some stretches of time, a warm and wet world. (The atmosphere was probably not thick enough to allow a stable climate to last billions of years). What is certain is that, during the "wet phases" of the Noachian Period, rivers flowed and water filled the craters and lowland basins of Mars, forming lakes and seas. 

NASA selected the name Curiosity for its rover following a competition. A 12-year-old student from Kansas, Clara Ma, submitted the winning entry. Clara wrote in her winning essay: "Curiosity is an everlasting flame that burns in everyone's mind ... Curiosity is the passion that drives us through our everyday lives. We have become explorers and scientists with our need to ask questions and to wonder."

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