Solar System/Mars

Mars is the fourth planet from the Sun and the second smallest (after Mercury), with a diameter of 6,794 kilometers (4,222 mi) (53% of that of Earth). Mars is one of the four terrestrial planets (planets having a solid surface). If you were standing on Mars, you would weigh just 38% of what you weigh on Earth.

True color photo of Mars.

Orbit

Mars orbit compared to earth orbit.

Mars orbits the Sun once every 1.8809 Earth-years, with an orbital eccentricity of 0.093—the greatest eccentricity of any planet except Mercury. It averages 1.52 times as far from the Sun as does Earth.

Rotation

Mars rotates about its axis prograde (in the same direction as its solar orbit) once every 24 hours 37 minutes 23 seconds. This is closer to one Earth-day than the rotational period of any other planet. Its axis is tilted by 25.19° relative to the perpendicular of its orbital plane; this is closer to Earth's axial tilt of 23.45° than that of any other planet.

Atmosphere

The atmosphere of Mars is slightly visible in this photograph.

Mars' atmosphere is made mostly of carbon dioxide (CO₂). Its atmosphere is 0.6% the pressure of Earth's atmosphere.

Wind

Photo of a Martian dust devil.

Climate

The average temperature for Mars was -63 °C (-81 °F). Mars was once habitable until 3.5 billion years ago.

Surface

Volcanism

Olympus Mons, an extremely large volcano.

Internal structure

Scientists of 19th century believed that life had gained a toehold on Mars. Canals were discovered on the red planet by Italian astronomer, Giovanni Schiaparelli in 1887. These appeared as markings on the surface of Mars. Scientists believed that these canals are constructed by intelligent beings to divert water from polar regions to the desert areas. Like Earth, Mars had seasons. In spring and summer, the colour of the dark areas of the Mars changed from bluish green to yellow. So, it was suspected that plant life thrived on Mars. However, the Mars probe, Mariner 4 sent home pictures of a lifeless planet. Ultraviolet radiation from the sun coupled with the special nature of soil prevents Life from gaining on toehold on Mars.

Satellites

Phobos

Phobos

Phobos is the larger and closer of Mars's two satellites, with a diameter of just 26 kilometers (16 mi) along one axis and just 18 kilometers (11 mi) along another axis. Of all the moons that are their planet's largest, Phobos is the smallest both in absolute terms and relative to its planet's size.

Deimos

Deimos

Deimos has a diameter of 16 kilometers (9.9 mi) along one axis and 10 kilometers (6.2 mi) along another.

Astronomers and Mars

In search of Martians

Sojourner

Launched in 1997. It has a 2 MHz CPU and 64K of RAM. It has a camera capable of shooting photos up to 484p.

Spirit and Opportunity

Both launched in 2004. Both have 20 MHz RAD6000 CPUs, 128 MB of RAM and 256 MB storage. Both have cameras capable of shooting photos up to 1024p.

Curiosity

Launched in 2011 and landed in 2012. It is currently operating. It has 200 MHz PowerPC 750 CPU, 256 MB of RAM and 2 GB storage. It has cameras capable of shooting photos up to 1200p and video up to 720p@10.

Perserverance

Launched in 2020 and landed in 2021. It is currently operating. It has 200 MHz PowerPC 750 CPU, 256 MB of RAM and 2 GB storage. It has cameras capable of shooting photos up to 5K and video up to 720p@10.