Mars
![Mars in true color,{{efn|The light filters are 635 nm, 546 nm, and 437 nm, roughly corresponding to red, green and blue respectively}} as captured by the [[Emirates Mars Mission|''Hope'']] orbiter. The [[Tharsis Montes]] can be seen at the center, with [[Olympus Mons]] just to the left and [[Valles Marineris]] at the right.](https://upload.wikimedia.org/wikipedia/commons/0/0c/Mars_-_August_30_2021_-_Flickr_-_Kevin_M._Gill.png)
The relatively flat plains in northern parts of Mars strongly contrast with the cratered terrain in southern highlands – this terrain observation is known as the Martian dichotomy. Mars hosts many enormous extinct volcanoes (the tallest is Olympus Mons, tall) and one of the largest canyons in the Solar System (Valles Marineris, long). Geologically, the planet is fairly active with marsquakes trembling underneath the ground, dust devils sweeping across the landscape, and cirrus clouds. Carbon dioxide is substantially present in Mars's polar ice caps and thin atmosphere. During a year, there are large surface temperature swings on the surface between to similar to Earth's seasons, as both planets have significant axial tilt.
Mars was formed approximately 4.5 billion years ago. During the Noachian period (4.5 to 3.5 billion years ago), Mars's surface was marked by meteor impacts, valley formation, erosion, and the possible presence of water oceans. The Hesperian period (3.5 to 3.3–2.9 billion years ago) was dominated by widespread volcanic activity and flooding that carved immense outflow channels. The Amazonian period, which continues to the present, has been marked by the wind as a dominant influence on geological processes. Due to Mars's geological history, the possibility of past or present life on Mars remains of great scientific interest.
Since the late 20th century, Mars has been explored by uncrewed spacecraft and rovers, with the first flyby by the ''Mariner 4'' probe in 1965, the first orbit by the ''Mars 2'' probe in 1971, and the first landing by the ''Viking 1'' probe in 1976. As of 2023, there are at least 11 active probes orbiting Mars or on the Martian surface. Mars is an attractive target for future human exploration missions, though in the 2020s no such mission is planned. Provided by Wikipedia
141
142
Published: c2001.
143
144
145
Published: 1993.
Superior document: Memoirs of the American Mathematical Society, Volume 106, Number 506
146
Published: 2004.
Superior document: Memoirs of the American Mathematical Society, Volume 168, Number 796
147
148
149
Published: 2007
Superior document: Cambridge Middle East studies 25
150
Published: 2001
Superior document: Basler Beiträge zur Physiogeographie : Physiogeographica 30
151
Published: c2008.
152
Published: c2010.
153
154
155
156
Published: 2010.
157
Published: 2011.
158
159
160
Published: 1376h.š, =, 1997
Superior document: Bunyānguḏārān-i farhang-i imrūz 29