Mars

Mars
Mars  is the fourth   planet  from the   Sun  and the second smallest planet in the   Solar System. Named after the   Roman  god of war, it is often described as the "Red Planet", as the   iron oxide  prevalent on its surface gives it a <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  reddish appearance<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. <sup class="reference" id="cite_ref-nasa_hematite_15-0" style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">[14] <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">Mars is a <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  terrestrial planet<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">with a thin <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  atmosphere<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, having surface features reminiscent both of the <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  impact craters<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">of the <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Moon<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">and the volcanoes, valleys, deserts, and <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  polar ice caps<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">of <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Earth<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">. The <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  rotational period<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">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 <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Olympus Mons<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, the second highest known mountain within the Solar System (the tallest on a planet), and of <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Valles Marineris<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, one of the largest canyons. The smooth <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Borealis basin<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">in the northern hemisphere covers 40% of the planet and may be a giant impact feature. <sup class="reference" id="cite_ref-northcratersn_16-0" style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">[15] <sup class="reference" id="cite_ref-northcraterguard_17-0" style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">[16] <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">Mars has two known <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  moons<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Phobos<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">and <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Deimos<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, which are small and irregularly shaped. These may be captured <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  asteroids<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  <sup class="reference" id="cite_ref-18" style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">[17] <sup class="reference" id="cite_ref-19" style="color:rgb(0,0,0);font-family:sans-serif;line-height:1em;">[18] <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, similar to <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  5261 Eureka<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">, a <span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">  Martian trojan asteroid<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19.1875px;">.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">Until the first successful Mars flyby in 1965 by Mariner 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed periodic variations in light and dark patches, particularly in the polar latitudes, which appeared to be seas and continents; long, dark striations were interpreted by some as irrigation channels for liquid water. These straight line features were later explained as optical illusions, though geological evidence gathered by unmanned missions suggest that Mars once had large-scale water coverage on its surface.<sup class="reference" id="cite_ref-marswater_20-0" style="line-height:1em;">[19]  In 2005, radar data revealed the presence of large quantities of water ice at the poles<sup class="reference" id="cite_ref-specials1_21-0" style="line-height:1em;">[20]  and at mid-latitudes.<sup class="reference" id="cite_ref-jsg.utexas.edu_22-0" style="line-height:1em;">[21] <sup class="reference" id="cite_ref-esa050221_23-0" style="line-height:1em;">[22]  The Mars rover Spirit sampled chemical compounds containing water molecules in March 2007. The Phoenix lander directly sampled water ice in shallow Martian soil on July 31, 2008.<sup class="reference" id="cite_ref-spacecraft1_24-0" style="line-height:1em;">[23]

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">Mars is currently host to five functioning spacecraft: three in orbit – the Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter; and two on the surface – Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity. Defunct spacecraft on the surface include MER-A Spirit, and several other inert landers and rovers, both successful and unsuccessful, such as the Phoenix lander, which completed its mission in 2008. Observations by the Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.<sup class="reference" id="cite_ref-NASA.C2.A0.E2.80.93_NASA_Spacecraft_Data_Suggest_Water_Flowing_on_Mars_25-0" style="line-height:1em;">[24]

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.1875px;color:rgb(0,0,0);font-family:sans-serif;">Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −3.0,<sup class="reference" id="cite_ref-MallamaSky_8-1" style="line-height:1em;">[7]  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 (186 miles) across when Earth and Mars are closest, because of Earth's atmosphere