Mars had a “close encounter” with Earth at 34.8 million miles apart.
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Asaph Hall discovered Mars' second moon, called Phobos.
NASA's Curiosity rover landed on Mars' Aeolis Palus plain.
The discovery of an Earth-like planet 3.2 times bigger than our world was announced.
University of California scientists found evidence that life on Earth probably began 4.1 billion years ago.
NASA launched the Mars Observer, a space probe designed to study Mars' geology and climate.
