Thirteen years. That is how long NASA’s Opportunity rover has now been exploring Meridiani Planum on Mars; not bad for a robot which was designed with a hoped-for nominal 90-day mission. Today marks the 13th anniversary of the landing of Opportunity, on Jan. 24, 2004 PST (Jan. 25, 2004 UTC). The mission since then has been nothing short of incredible, as Opportunity soon found evidence that Meridiani Planum used to be a much wetter place than it is now. It was a place where microbial life could have existed; whether it actually did or not is still unknown but Opportunity continues to provide more clues as it continues exploring vast sandy plains and mountainous crater rims.