| The most detailed information available about Mars has come from unpiloted spacecraft sent to the planet by the United States. From this data, scientists have determined that the planet’s atmosphere consists primarily of carbon dioxide, with small amounts of nitrogen, oxygen, water vapor, and other gases. Because the atmosphere is extremely thin, daily temperatures can vary as much as 100 Celsius degrees (190 Fahrenheit degrees). In general, surface temperatures are too cold and surface pressures too low for water to exist in a liquid state on Mars. The planet resembles a cold, high-altitude desert. |
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