Mars is the fourth solar system planet from the Sun and the second smallest. Characteristics:
It has two small moons, Phobos and Deimos both smaller than 25km in diameter. There has been interest in whether it might harbor life, and the fact that it is within the Sun's habitable zone makes the idea plausible. But the average surface temperature is on the order of -70 centigrade, and at Mars atmospheric pressure, below water's triple point making liquid water unlikely, and the ground with water is generally locked in permafrost, all decreasing the likelihood of identifying a location that could support life. There is evidence of water on Mars's surface earlier in its life but that may not have lasted very long.
Mars's axial tilt cycles over a wider range than Earth's, largely due to its lack of such influence as the Moon has on Earth's. This results in Mars's more pronounced climate changes over the long term.
Far more space missions have been sent to Mars than to any other planet, more than 40, beginning in the 1960s with the NASA Mariner and Viking programs and the Soviet Mars program. Recent years have had orbiters (e.g., NASA's Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO)), landers (e.g., NASA's Phoenix), rovers (e.g., NASA's Mars Exploration Rover and Curiosity), and other missions Swinging By. From the orbiting and landing probes much of Mars' geography and geology has been mapped and investigated: the huge volcano, Olympus Mons, taller than any mountain on Earth, and the Medusae Fossae Formation (MFF), a large region of flat lowlands that appears to be a lava deposit.
Future missions and proposals include missions from numerous countries: Mars 2020 from NASA, and others by the EU, Japan, Russia, China, and other countries, including the ExoMars, rover mission from the European Space Agency and Russia.