On this day: August 20

Published On: Aug 19 2012 02:46:11 AM CDT   Updated On: Aug 20 2014 01:00:00 AM CDT

Charles Darwin publishes his theory of evolution, the NFL is founded, Lou Gehrig belts his 23rd career grand slam and NASA heads for Mars, all on this day.

OTD August 20 - Viking 1
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NASA

1975: NASA launches the Viking 1 planetary probe toward Mars. It eventually became the first spacecraft to successfully land on Mars and perform its mission, and held the record for the longest Mars surface mission of six years and 116 days until that record was broken by the Opportunity Rover on May 19, 2010.

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