# Mars By [Gor](https://paragraph.com/@gor) · 2024-01-17 --- **Mars** is the fourth [planet](https://en.wikipedia.org/wiki/Planet) from the [Sun](https://en.wikipedia.org/wiki/Sun). The [surface of Mars is orange-red](https://en.wikipedia.org/wiki/Mars_surface_color) because it is covered in [iron(III) oxide](https://en.wikipedia.org/wiki/Iron\(III\)_oxide) dust, giving it the nickname "**the Red Planet**".[\[21\]](https://en.wikipedia.org/wiki/Mars#cite_note-Rees2012-23)[\[22\]](https://en.wikipedia.org/wiki/Mars#cite_note-nasa_hematite-24) Mars hosts many enormous extinct [volcanos](https://en.wikipedia.org/wiki/Volcanos) (such as [Olympus Mons](https://en.wikipedia.org/wiki/Olympus_Mons), 21.9 km or 13.6 mi tall) and one of the largest [canyons](https://en.wikipedia.org/wiki/Canyon) in the Solar System ([Valles Marineris](https://en.wikipedia.org/wiki/Valles_Marineris), 4,000 km or 2,500 mi long). For comparison, Mars's diameter is 6,779 km (4,212 mi). It is classified as a [terrestrial planet](https://en.wikipedia.org/wiki/Terrestrial_planet) and is the second smallest of the [Solar System](https://en.wikipedia.org/wiki/Solar_System)'s planets. When viewed closely, the relatively flat [plains](https://en.wikipedia.org/wiki/Plain) in northern parts of Mars strongly contrast with the cratered terrain in southern [highlands](https://en.wikipedia.org/wiki/Highland) – this terrain observation is known as the [Martian dichotomy](https://en.wikipedia.org/wiki/Martian_dichotomy). Geologically, the planet is fairly active with [marsquakes](https://en.wikipedia.org/wiki/Marsquake) trembling underneath the ground, [dust devils](https://en.wikipedia.org/wiki/Martian_dust_devils) sweeping across the landscape, and [cirrus clouds](https://en.wikipedia.org/wiki/Cirrus_cloud). [Carbon dioxide](https://en.wikipedia.org/wiki/Carbon_dioxide) are substantially present in Mars's [polar ice caps](https://en.wikipedia.org/wiki/Polar_ice_cap) and [thin atmosphere](https://en.wikipedia.org/wiki/Atmosphere_of_Mars). In terms of orbital motion, a Martian solar day ([sol](https://en.wikipedia.org/wiki/Mars_sol)) is equal to 24.5 hours and a [Martian solar year](https://en.wikipedia.org/wiki/Timekeeping_on_Mars) is equal to 1.88 Earth years (687 Earth days). During a year, there are large surface temperature swings on the surface between −78.5 °C (−109.3 °F) to 5.7 °C (42.3 °F)[\[c\]](https://en.wikipedia.org/wiki/Mars#cite_note-25) similar to Earth's [seasons](https://en.wikipedia.org/wiki/Season), as both planets have significant [orbital eccentricity](https://en.wikipedia.org/wiki/Orbital_eccentricity) and [axial tilt](https://en.wikipedia.org/wiki/Axial_tilt). Mars has [two natural satellites](https://en.wikipedia.org/wiki/Moons_of_Mars) that are small and irregular in shape: [Phobos](https://en.wikipedia.org/wiki/Phobos_\(moon\)) and [Deimos](https://en.wikipedia.org/wiki/Deimos_\(moon\)). Mars was formed approximately 4.5 billion years ago. During the [Noachian](https://en.wikipedia.org/wiki/Noachian) period (4.5 to 3.5 billion years ago), Mars's surface was marked by [meteor impacts](https://en.wikipedia.org/wiki/Impact_event), valley formation, erosion, and the possible presence of water [oceans](https://en.wikipedia.org/wiki/Ocean). The [Hesperian](https://en.wikipedia.org/wiki/Hesperian) period (3.5 to 3.3–2.9 billion years ago) was dominated by widespread [volcanic activity](https://en.wikipedia.org/wiki/Volcanism) and flooding that carved immense [outflow channels](https://en.wikipedia.org/wiki/Outflow_channels). The [Amazonian](https://en.wikipedia.org/wiki/Amazonian_\(Mars\)) period, which continues to the present, was marked by the [wind as a dominant influence on geological processes](https://en.wikipedia.org/wiki/Aeolian_processes). It is unknown whether [life has ever existed on Mars](https://en.wikipedia.org/wiki/Life_on_Mars). Mars is among [the brightest objects in Earth's sky](https://en.wikipedia.org/wiki/List_of_brightest_natural_objects_in_the_sky) and its high-contrast [albedo features](https://en.wikipedia.org/wiki/Albedo_feature) have make it a common subject for [telescope](https://en.wikipedia.org/wiki/Telescope) viewing. Since the late 20th century, [Mars has been explored by uncrewed spacecraft and rovers](https://en.wikipedia.org/wiki/Exploration_of_Mars), with the first flyby by the [_Mariner 4_](https://en.wikipedia.org/wiki/Mariner_4) probe in 1965, the first Mars orbiter by the [_Mars 2_](https://en.wikipedia.org/wiki/Mars_2) probe in 1971, and the first landing by the [_Viking 1_](https://en.wikipedia.org/wiki/Viking_1) probe in 1976. As of 2023, there are at least 11 active probes orbiting Mars or at the Martian surface. Mars is an attractive target for future [human exploration missions](https://en.wikipedia.org/wiki/Human_mission_to_Mars), though in the 2020s no such mission is planned. --- *Originally published on [Gor](https://paragraph.com/@gor/mars)*