Query: Now scientists are telling us that Mars is experiencing its own planetary warming: Martian warming.

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Mars ocean hypothesis <=SEP=> The Mars ocean hypothesis states that nearly a third of the surface of Mars was covered by an ocean of liquid water early in the planet 's geologic history . This primordial ocean , dubbed Paleo-Ocean and Oceanus Borealis , would have filled the basin Vastitas Borealis in the northern hemisphere , a region which lies 4 -- 5 km ( 2.5 -- 3 miles ) below the mean planetary elevation , at a time period of approximately 4.1 -- 3.8 billion years ago . Evidence for this ocean includes geographic features resembling ancient shorelines , and the chemical properties of the Martian soil and atmosphere . Early Mars would have required a denser atmosphere and warmer climate to allow liquid water to remain at the surface .

Mars <=SEP=> Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System , after Mercury . Named after the Roman god of war , it is often referred to as the `` Red Planet '' because the iron oxide prevalent on its surface gives it a reddish appearance . Mars is a terrestrial planet with a thin atmosphere , having surface features reminiscent both of the impact craters of the Moon and the valleys , deserts , and polar ice caps of Earth .   The rotational period and seasonal cycles of Mars are likewise similar to those of Earth , as is the tilt that produces the seasons . Mars is the site of Olympus Mons , the largest volcano and second-highest known mountain in the Solar System , and of Valles Marineris , one of the largest canyons in the Solar System . The smooth Borealis basin in the northern hemisphere covers 40 % of the planet and may be a giant impact feature . Mars has two moons , Phobos and Deimos , which are small and irregularly shaped . These may be captured asteroids , similar to 5261 Eureka , a Mars trojan .   There are ongoing investigations assessing the past habitability potential of Mars , as well as the possibility of extant life . Future astrobiology missions are planned , including the Mars 2020 and ExoMars rovers . Liquid water can not exist on the surface of Mars due to low atmospheric pressure , which is about that of the Earth 's , except at the lowest elevations for short periods . The two polar ice caps appear to be made largely of water . The volume of water ice in the south polar ice cap , if melted , would be sufficient to cover the entire planetary surface to a depth of 11 m . In November 2016 , NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars . The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior .   Mars can easily be seen from Earth with the naked eye , as can its reddish coloring . Its apparent magnitude reaches − 2.91 , which is surpassed only by Jupiter , Venus , the Moon , and the Sun . Optical ground-based telescopes are typically limited to resolving features about 300 km across when Earth and Mars are closest because of Earth 's atmosphere .

Martian <=SEP=> A Martian is a native inhabitant of the planet Mars . Although the search for evidence of life on Mars continues , many science fiction writers have imagined what extraterrestrial life on Mars might be like . Some writers also use the word Martian to describe a human colonist on Mars .

Extraterrestrial atmosphere <=SEP=> The study of extraterrestrial atmospheres is an active field of research , both as an aspect of astronomy and to gain insight into Earth 's atmosphere . In addition to Earth , many of the other astronomical objects in the Solar System have atmospheres . These include all the gas giants , as well as Mars , Venus , and Pluto . Several moons and other bodies also have atmospheres , as do comets and the Sun . There is evidence that extrasolar planets can have an atmosphere . Comparisons of these atmospheres to one another and to Earth 's atmosphere broaden our basic understanding of atmospheric processes such as the greenhouse effect , aerosol and cloud physics , and atmospheric chemistry and dynamics .