Free Astronomy Magazine March-April 2021

a total of one kilometer. Both rovers exceeded by many years the mis- sion's expected duration, which was estimated at just 90 days. Spirit lasted over 20 times longer than the nominal mission, traveling 7.7 km in- stead of the expected 600 meters. Opportunity worked on Mars longer than any other human artifact: near- ly 15 years. It communicated for the last time with the Earth on June 10, 2018. Three years earlier, Opportu- nity had broken the record for “ex- traterrestrial driving” by exceeding the distance of a marathon, at a total journey of over 45 kilometers. Moving from place to place, the two rovers carried out geological surveys on various sites. Each rover was a kind of robot geologist that tra- versed the surface of Mars. The cameras mounted at a height of 1.5 meters provided a 360-degree stereoscopic view of the area. A ro- A bove left, the rock called “Wishstone”, abraded by Spirit with the Rock Abrasion Tool (RAT), to examine the internal composi- tion, found to be rich in phospho- rus. Next, a terrain strewn with dark volcanic rocks. Further to the right, a rocky outcrop called “Gas- conade”, studied by Opportunity, near the western end of the En- deavor Crater. [NASA/JPL-Caltech/ Cornell/ NMMN/USGS/ASU]