Published: May 21, 2010

2,246: And counting. As of Thursday, the number of Martian days (each of which, in Earth time, is 24 hours, 39 minutes and 35 seconds) that the NASA rover Opportunity had explored the surface of Mars, surpassing the record set by the Viking 1 lander in November 1982. The rover was designed for a three-month mission. “I thought we’d get six months,” said Steven W. Squyres, an astronomy professor at Cornell and principal investigator for the project. “Six years? No.” At last report, the Opportunity was on its way to a large crater, named Endeavour, that it will not reach for two more years. If it lasts that long.