page_title: Climate of Mars
section_title: Weather
hierarchical_section_title: Climate of Mars / Weather
caption_attribution_description: English: PIA17940: Martian Morning Clouds Seen by Viking Orbiter 1 in 1976 http://photojournal.jpl.nasa.gov/catalog/PIA17940 No NASA Mars orbiter has been in a position to observe morning daylight on Mars since the twin Viking orbiters of the 1970s. This image, taken by Viking Orbiter 1 on Aug. 17, 1976, shows water-ice clouds in the Valles Marineris area of equatorial Mars during local morning time. North is to the upper left, and the scene is about 600 miles (about 1,000 kilometers) across. Although a few observations of Mars in morning daylight have come from the Viking orbiters and the European Space Agency's Mars Express orbiter, no mission has systematically studied how morning features such as clouds, fogs and surface frost develop in different Martian seasons in different parts of the planet. NASA's Mars Odyssey orbiter, in 2014, is in the process of changing its orbit to enable such systematic morning daylight observations. JPL manages Odyssey for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems built the spacecraft and collaborates with JPL in mission operations. For more about the Mars Odyssey mission, visit http://mars.jpl.nasa.gov/odyssey.
context_page_description: The climate of Mars has been a topic of scientific curiosity for centuries, in part because it is the only terrestrial planet whose surface can be directly observed in detail from the Earth with help from a telescope.
  Although Mars is smaller than the Earth, 11% of Earth's mass, and 50% farther from the Sun than the Earth, its climate has important similarities, such as the presence of polar ice caps, seasonal changes and observable weather patterns. It has attracted sustained study from planetologists and climatologists. While Mars' climate has similarities to Earth's, including periodic ice ages, there are also important differences, such as much lower thermal inertia. Mars' atmosphere has a scale height of approximately 11 km, 60% greater than that on Earth. The climate is of considerable relevance to the question of whether life is or was present on the planet.
context_section_description: Mars' temperature and circulation vary every Martian year (as expected for any planet with an atmosphere and axial tilt). Mars lacks oceans, a source of much interannual variation on Earth. Mars Orbiter Camera data beginning in March 1999 and covering 2.5 Martian years show that Martian weather tends to be more repeatable and hence more predictable than that of Earth. If an event occurs at a particular time of year in one year, the available data (sparse as it is) indicates that it is fairly likely to repeat the next year at nearly the same location, give or take a week.
  On September 29, 2008, the Phoenix lander detected snow falling from clouds 4.5 kilometres (2.8 mi) above its landing site near Heimdal Crater. The precipitation vaporised before reaching the ground, a phenomenon called virga.
caption: Martian morning clouds (Viking Orbiter 1, 1976)
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