Mars

Martian Panorama by Mars Exploration Rover Opportunity Credit: NASA

Mars is the fourth planet from the Sun and is the second smallest planet in the solar system. Named after the Roman god of war, Mars is also often described as the “Red Planet” due to its reddish appearance. Mars is a terrestrial planet with a thin atmosphere composed primarily of carbon dioxide.

Equatorial Diameter: 6,792 km

Polar Diameter: 6,752 km

Mass: 6.42 x 10^23 kg (10.7% Earth)

Moons: 2 (Phobos & Deimos)

Orbit Distance: 227,943,824 km (1.52 AU)

Orbit Period: 687 days (1.9 years)

Surface Temperature: -153 to 20 °C

Mars is home to the tallest mountain in the solar system. Olympus Mons, a shield volcano, is 21km high and 600km in diameter. Despite having formed over billions of years, evidence from volcanic lava flows is so recent many scientists believe it could still be active.

Mars has the largest dust storms in the solar system. They can last for months and cover the entire planet. The seasons are extreme because its elliptical (oval-shaped) orbital path around the Sun is more elongated than most other planets in the solar system.

Pieces of Mars have fallen to Earth. Scientists have found tiny traces of Martian atmosphere within meteorites violently ejected from Mars, then orbiting the solar system among galactic debris for millions of years, before crash landing on Earth. This allowed scientists to begin studying Mars prior to launching space missions.

Significant Dates:

• 1877: Asaph Hall discovers the two moons of Mars, Phobos and Deimos.
• 1965: NASA's Mariner 4 sends back 22 photos of Mars, the world's first close-up photos of a planet beyond Earth.
• 1976: Viking 1 and 2 land on the surface of Mars.
• 1997: Mars Pathfinder lands and dispatches Sojourner, the first wheeled rover to explore the surface of another planet.
• 2002: Mars Odyssey begins its mission to make global observations and find buried water ice on Mars.
• 2004: Twin Mars Exploration Rovers named Spirit and Opportunity find strong evidence that Mars once had long-term liquid water on the surface.
• 2006: Mars Reconnaissance Orbiter begins returning high-resolution images as it studies the history of water on Mars and seasonal changes.
• 2008: Phoenix finds signs of possible habitability, including the occasional presence of liquid water and potentially favorable soil chemistry.
• 2012: NASA's Mars rover Curiosity lands in Gale Crater and finds conditions once suited for ancient microbial life on Mars.
• 2014: On September 24 Indian Space Research Organisation (ISRO) Mars Orbiter Mission (MOM) inserted into Mars's orbit.

Credit: Karl Tate/Space.com

Reference: Karl Tate/spacedotcom/Nasa Solar System