The Planets. Professor Cox Brian

high enough to see basketball-sized features on the Martian surface. The Mars Color Imager (MARCI) camera monitors Martian weather, and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) identifies mineral deposits, particularly those formed in the presence of surface water.

      Orbiting with the MRO is the Mars Atmosphere and Volatile Evolution Mission (MAVEN). This camera-less spacecraft operates between 150 kilometres and 6,000 kilometres above the Martian surface, measuring the composition of the atmosphere at different altitudes and observing how the tenuous gases are stripped from the planet by the solar wind.

      Mars Odyssey is the veteran of the orbiting fleet, having arrived in 2001 and still being operational in a polar orbit, searching primarily for water ice on the surface. Mars Express is a European Space Agency mission that is delivering high-resolution photographs, mineralogy data, radar investigation of the near sub-surface and atmospheric measurements, including the search for methane, a gas that on Earth is associated with biological activity. India’s Mangalyaan space probe is primarily a technology demonstrator, but it carries a secondary scientific package capable of investigating atmospheric composition.

      ‘It may be — it may just be that life as we know it with its humanity is more unique than many have thought, and we must remember this.’

      President Lyndon B. Johnson

      © NASA/JPL-Caltech

      An Opportunity eye view of the surface of Mars, taken from the rover’s front hazard-avoidance camera (Hazcam).

      The newest arrival at Mars is the joint European Space Agency/Russian ExoMars Trace Gas Orbiter, which will observe seasonal changes in the Martian atmosphere and search for subsurface water deposits. The spacecraft will form the communications bridge for ESA’s ExoMars rover, due to land in 2021.

      The two most recent explorers of Mars are the Opportunity and Curiosity rovers. The Opportunity rover landed on the Meridiani Planum close to the Martian equator on 25 January 2004, with a planned lifetime of 90 Earth days. In a spectacular testament to the Jet Propulsion Laboratory’s engineering excellence, Opportunity remained operational until a planet-wide dust storm covered its solar panels in June 2018, after over 14 years and a journey of 45 kilometres on the surface of Mars, exploring the Endurance, Victoria and Endeavour craters. On 13 February 2019, Opportunity was finally declared ‘dead’.