Editing Extraterrestrial life (section)

===19th century===
[[File:Lowell Mars channels.jpg|thumb|Artificial Martian channels, depicted by Percival Lowell]]
Speculation about life on Mars increased in the late 19th century, following telescopic observation of apparent [[Martian canals]] – which soon, however, turned out to be optical illusions.<ref>{{cite journal |title=Experiments as to the actuality of the "Canals" observed on Mars |journal=Monthly Notices of the Royal Astronomical Society |first1=J. E. |last1=Evans |first2=E. W. |last2=Maunder |author2-link=Edward Walter Maunder |volume=63 |issue=8 |pages=488–499 |date=June 1903 |doi=10.1093/mnras/63.8.488 |bibcode=1903MNRAS..63..488E|url=https://zenodo.org/record/1431867 |doi-access=free }}</ref> Despite this, in 1895, American astronomer [[Percival Lowell]] published his book ''Mars,'' followed by ''Mars and its Canals'' in 1906, proposing that the canals were the work of a long-gone civilisation.<ref name="Wallace1907">{{cite book |url=http://people.wku.edu/charles.smith/wallace/S730.htm |title=Is Mars Habitable? A Critical Examination of Professor Lowell's Book "Mars and Its Canals," With an Alternative Explanation |publisher=Macmillan |location=London |first=Alfred Russel |last=Wallace |date=1907 |oclc=8257449}}</ref> 

[[Spectroscopy|Spectroscopic]] analysis of Mars's atmosphere began in earnest in 1894, when U.S. astronomer [[William Wallace Campbell]] showed that neither water nor oxygen was present in the [[Martian atmosphere]].<ref name="chambers">{{Cite book |first=Paul |last=Chambers |title=Life on Mars; The Complete Story |place=London |publisher=Blandford |year=1999 |isbn=978-0-7137-2747-0 |url=https://archive.org/details/lifeonmarscomple00cham }}</ref> By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal hypothesis.<ref>{{Cite web |title=Seeing and Interpreting Martian Oceans and Canals {{!}} Life on Other Worlds {{!}} Articles and Essays {{!}} Finding Our Place in the Cosmos: From Galileo to Sagan and Beyond {{!}} Digital Collections {{!}} Library of Congress |url=https://www.loc.gov/collections/finding-our-place-in-the-cosmos-with-carl-sagan/articles-and-essays/life-on-other-worlds/seeing-and-interpreting-martian-oceans-and-canals |access-date=2024-05-10 |website=Library of Congress, Washington, D.C. 20540 USA}}</ref>

As a consequence of the belief in the [[spontaneous generation]] there was little thought about the conditions of each celestial body: it was simply assumed that life would thrive anywhere. This theory was disproved by [[Louis Pasteur]] in the 19th century. Popular belief in thriving alien civilisations elsewhere in the solar system still remained strong until [[Mariner 4]] and [[Mariner 9]] provided close images of Mars, which debunked forever the idea of the existence of Martians and decreased the previous expectations of finding alien life in general.<ref>Aguilera Mochon, pp. 8–9</ref> The end of the spontaneous generation belief forced investigation into the origin of life. Although [[abiogenesis]] is the more accepted theory, a number of authors reclaimed the term "panspermia" and proposed that life was brought to Earth from elsewhere.<ref name="Anaxagoras"/> Some of those authors are [[Jöns Jacob Berzelius]] (1834),<ref>{{Cite journal |title=Analysis of the Alais meteorite and implications about life in other worlds |journal=[[Liebigs Annalen|Annalen der Chemie und Pharmacie]] |first=Jöns Jacob |last=Berzelius |author-link=Jöns Jacob Berzelius |volume=10 |pages=134–135 |date=1834}}</ref> [[William Thomson, 1st Baron Kelvin|Kelvin]] (1871),<ref>{{Cite journal |title=The British Association Meeting at Edinburgh |journal=Nature |first=William |last=Thomson |author-link=William Thomson, 1st Baron Kelvin |volume=4 |issue=92 |pages=261–278 |date=August 1871 |doi=10.1038/004261a0 |bibcode=1871Natur...4..261. |quote=We must regard it as probably to the highest degree that there are countless seed-bearing meteoritic stones moving through space. |pmc=2070380}}</ref> [[Hermann von Helmholtz]] (1879)<ref>{{cite journal |title=Darwin's Contribution to the Development of the Panspermia Theory |journal=Astrobiology |first=René |last=Demets |volume=12 |issue=10 |pages=946–950 |date=October 2012 |doi=10.1089/ast.2011.0790 |pmid=23078643 |bibcode=2012AsBio..12..946D}}</ref> and, somewhat later, by [[Svante Arrhenius]] (1903).<ref>{{cite book |url=https://archive.org/details/worldsinmakingev00arrhrich |title=Worlds in the Making: The Evolution of the Universe |publisher=Harper & Brothers |first=Svante |last=Arrhenius |others=trans. H. Borns |date=March 1908 |oclc=1935295}}</ref>

The science fiction genre, although not so named during the time, developed during the late 19th century. The expansion of the genre of [[extraterrestrials in fiction]] influenced the popular perception over the real-life topic, making people eager to jump to conclusions about the discovery of aliens. Science marched at a slower pace, some discoveries fueled expectations and others dashed excessive hopes. For example, with the advent of telescopes, most structures seen on the Moon or Mars were immediately attributed to Selenites or Martians, and later ones (such as more powerful telescopes) revealed that all such discoveries were natural features.<ref name="AM8"/> A famous case is the [[Cydonia (Mars)|Cydonia]] region of Mars, first imaged by the ''[[Viking 1]]'' orbiter. The low-resolution photos showed a rock formation that resembled a human face, but later spacecraft took photos in higher detail that showed that there was nothing special about the site.<ref>{{cite web |url= https://www.space.com/17191-face-on-mars.html|title= The Face on Mars: Fact & Fiction|author= Nola Taylor Tillman |date= August 20, 2012|publisher= Space.com|accessdate=September 18, 2022}}</ref>