query: What is the temperature on Mars?
passage: Climate of Mars
Differing in situ values have been reported for the average temperature on Mars,[21] with a common value being −63°C (210K; −81°F).[22][23] Surface temperatures may reach a high of about 20°C (293K; 68°F) at noon, at the equator, and a low of about −153°C (120K; −243°F) at the poles.[24] Actual temperature measurements at the Viking landers' site range from −17.2°C (256.0K; 1.0°F) to −107°C (166K; −161°F). The warmest soil temperature estimated by the Viking Orbiter was 27°C (300K; 81°F).[25] The Spirit rover recorded a maximum daytime air temperature in the shade of 35°C (308K; 95°F), and regularly recorded temperatures well above 0°C (273K; 32°F), except in winter.[26]
passage: Climate of Mars
Recent observations and modeling are producing information not only about the present climate and atmospheric conditions on Mars but also about its past. The Noachian-era Martian atmosphere had long been theorized to be carbon dioxide–rich. Recent spectral observations of deposits of clay minerals on Mars and modeling of clay mineral formation conditions[5] have found that there is little to no carbonate present in clay of that era. Clay formation in a carbon dioxide–rich environment is always accompanied by carbonate formation, although the carbonate may later be dissolved by volcanic acidity.