Spirit: travel diary

10 June 2003: You leave Florida. Your mission is to find water on Mars, landing in Gusev crater. Sol 1, 4 January 2004: After nearly seven months, you arrive inside an airbag. Twenty-eight bounces later you stop. Dust-devil tracks criss-cross the landing site. You roll out of Columbia Memorial Station onto a rocky plain. Expecting a dry lake bed, you instead find volcanic basalt mixed with impact debris, with no obvious volcano. You have just arrived and already face a mystery. Sol 18: After entering sleep mode, the computer restarts repeatedly without stopping. Sol 32: The fault is resolved by deleting more than 6,000 unnecessary files and reformatting storage. Sol 60: You drill Humphrey, a volcanic rock with vesicles through which water circulated while volcanism kept the ground hot. Sol 108: AutoNav becomes stuck among rocks, searching for a route for 105 minutes and giving up after 47 attempts. Sols 239–262: Solar conjunction interrupts radio communication. Two weeks of rest! Sol 343: A wheel sinks into loose material and traps a potato-shaped stone, which falls out three sols later. Sols 360–370: You climb Husband Hill through progressively younger rock layers. Sol 400: At Paso Robles, iron sulphates in pale soil suggest acidic hydrothermal springs or fumaroles. Sol 420, 2005: A passing dust devil cleans the solar panels. Such vortices also occur over dry ground on Earth, becoming visible when they lift dust. Sol 489: You photograph sunset behind the crater wall eighty kilometres away. The Martian sky glows bluish at this time. Sols 583–586: You create a panoramic self-portrait.

Sol 690, Comanche Point: You find carbonate-rich rock. Carbonate would dissolve in acidic water, so this indicates neutral-pH water, ideal for microbes. Here it formed as volcanic minerals altered in hot water in contact with atmospheric carbon dioxide. Sol 744: You reach Home Plate, a two-metre-high plateau. Sol 778, 2006: The right wheel jams. You reverse, dragging the stationary wheel. Sol 811: You park for eight Earth months at Low Ridge Haven to survive winter, choosing a ten-degree slope that gives the solar panels enough sunlight for one hour of daily operation. Sol 1202, 2007: At Silica Valley you find quartz precipitated from geysers where hot vapour moved through rock cracks. Sol 1657, 2008: You park on a thirty-degree north-facing slope and hibernate the computer. Daily power is 235 Wh, formerly 700 Wh. From February to October you slowly photograph the Bonestell Panorama. There is no hurry. Sol 1724, 9 November 2008, Mars Year 29, Ls 327°: A dust storm reduces solar output to 89 Wh. Keeping the electronics warm requires 150 Wh per sol, so the batteries slowly drain. Temperatures are −85 °C at night and −20 °C by day. Sol 1763: You spin the middle wheel to shake dust off the panels. On a thirty-degree slope—the steepest you can hold—you climb 23 cm but slide back six. You turn around. Sol 1892, 2009: A sand trap! The desert crust collapses above soft iron sulphate, jarosite, and the wheel spins in place. Sol 2097: The rear-right wheel fails. Winter catches you on flat ground, without enough sunlight for charging and heating. Renaming yourself a stationary research platform does not solve the problem. In your fourth long winter, you study weather and photograph the tracks made when you could still move. Sols 2191–2208: Each day you photograph only the Sun. Sol 2210, 2010, Mars Year 30, Ls 143°: You send your last message from Troy. The panels produce 134 Wh. Temperatures are −93 °C at night and −33 °C by day. Inside, the temperature drops below the critical −40 °C. The computer hibernates and the clock stops. Time has stopped for you. 24 May 2011: Earth makes its final attempt to awaken you. The signal arrives, but you can no longer hear it. Your mission has ended.