2001 Mars Odyssey (named after the famed novel/film 2001: A Space Odyssey by Stanley Kubrick and Arthur C. Clarke) is a NASA space probe orbiting Mars since 2001-Oct-25. This satellite provided the first hints of traces of water present on modern-day Mars, and assisted in relaying communications with all surface landers and rovers since 2004. Clocking in at over 20 years, it is the longest mission to Mars ever attempted, and is expected to remain active until at least 2025
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