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'''Mars''' is the fourth planet from the [[Sun]], after [[Mercury]], [[Venus]], and [[Earth]]. It is called "The Red Planet" because it looks red from Earth.  

'''Mars''' is the fourth planet from the [[Sun]], after [[Mercury]], [[Venus]], and [[Earth]]. It is called "The Red Planet" because of the iron oxide which comprises its suface.  

== Ancient knowledge and naming ==

== Ancient knowledge and naming ==

== Life on Mars ==

== Life on Mars ==

The possibility that [[extraterrestrial life]] exists on Mars has been the subject of persistent scientific speculation for decades. The earliest speculation concerned a possible civilization on Mars,<ref name=Hamilton/> this after Percival Lowell theorized that the straight lines that several astronomers had seen on Mars were in fact artificial constructs, and specifically canals.<ref name=canals>"[http://ssed.gsfc.nasa.gov/tharsis/canals.html The canals of Mars--historical note]." Goddard Space Flight Center, [[National Aeronautics and Space Administration|NASA]], n.d. Accessed May 27, 2008.</ref> Lovell popularized his theory as early as 1906, and for a long time the suspicion of a non-human civilization native to Mars would find repeated expression in novels and dramatic presentations. Only with the first successful explorations of Mars would the scientific community, and the public, abandon that theory.

The possibility that [[extraterrestrial life]] exists, or has existed, on Mars has been the subject of persistent scientific speculation for decades. The earliest speculation concerned a possible civilization on Mars,<ref name=Hamilton/> this after Percival Lowell theorized that the straight lines that several astronomers had seen on Mars were in fact artificial constructs, and specifically canals.<ref name=canals>"[http://ssed.gsfc.nasa.gov/tharsis/canals.html The canals of Mars--historical note]." Goddard Space Flight Center, [[National Aeronautics and Space Administration|NASA]], n.d. Accessed May 27, 2008.</ref> Lovell popularized his theory as early as 1906, and for a long time the suspicion of a non-human civilization native to Mars would find repeated expression in novels and dramatic presentations. Only with the first successful explorations of Mars would the scientific community, and the public, abandon that theory.

Current speculation concerns the possible finding of [[microbe]]s. These would be [[extremophile]]s, or microbes that survive and even grow in environments lethal to other forms of life. Direct attempts to find such life began in 1976 with the [[Viking 1]] and [[Viking 2]] landers. To date no positive sign of life on Mars has been found. The Viking landers found evidence of unexplained chemical activity, but no clear evidence of microbes. Whether the Viking landers would have been able to detect extremophiles, a concept unknown to the Viking mission planners, is unclear.<ref name=Hamilton/>

Current speculation concerns the possible finding of [[microbe]]s. These would be [[extremophile]]s, or microbes that survive and even grow in environments lethal to other forms of life. Direct attempts to find such life began in 1976 with the [[Viking 1]] and [[Viking 2]] landers. To date no positive sign of life on Mars has been found. The Viking landers found evidence of unexplained chemical activity, but no clear evidence of microbes. Whether the Viking landers would have been able to detect extremophiles, a concept unknown to the Viking mission planners, is unclear.<ref name=Hamilton/>