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664:. Historically, planets reflecting light in the green-yellow range were sought out as possible hosts to photosynthetic organisms, due to the implied presence of chlorophyll. The hypothesis suggests that search methods should be expanded to planets reflecting blue and red light, since evolution of retinal-based photosynthesis is also probable, or possibly even more likely than the evolution of chlorophyllic systems.
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640:, dictating that chlorophyllic organisms cannot re-adapt to absorb the energy-rich and now-available green light, and therefore ended up reflecting and presenting a greenish color. The subsequent success of more advanced chlorophyllic organisms (particularly
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492:, where they may utilize complementary regions of the solar spectrum. Co-existence of purple and green pigment-containing microorganisms in many environments suggests their co-evolution.
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Astrobiologists have suggested that retinal pigments may serve as remote biosignatures in exoplanet research. The Purple Earth hypothesis has great implications for the search for
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Sparks, William B.; DasSarma, S.; Reid, I. N. (December 2006). "Evolutionary
Competition Between Primitive Photosynthetic Systems: Existence of an early purple Earth?".
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membrane components in ancient sediments on the Early Earth are consistent with an early appearance of life forms with purple membranes prior to the turquoise of the
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It is possible that the Early Earth's biosphere was initially dominated by retinal-powered archaeal colonies that absorbed all the green light, leaving the
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color. Chlorophyll pigments, in contrast, absorb red and blue light, but little or no green light, which results in the characteristic green reflection of
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Schwieterman, Edward W.; Kiang, Nancy Y.; Parenteau, Mary N.; Harman, Chester E.; DasSarma, Shiladitya; Fisher, Theresa M.; Arney, Giada N.;
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and the photosynthetic cyanobacteria) to exploit and prosper. This also forced the surviving anaerobes to either live only in
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An example of retinal-based organisms that exist today are photosynthetic microbes collectively called
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life among aerobes (whose colonies would sometimes consume enough free oxygen to create pockets of
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color. It is estimated to have occurred between 3.5 and 2.4 billion years ago during the
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membrane components in ancient sediments on the Early Earth support the PEH.
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Stoeckenius, Walther (1976). "The purple membrane of salt-loving bacteria".
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evolved and started to photosynthesize, which included both the primitive
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between anaerobic archaea and aerobic eubacteria (which evolved into
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Astrobiological hypothesis regarding early photosynethetic organisms
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However, the porphyrin-based nature of chlorophyll had created an
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DasSarma, Shiladitya; Schwieterman, Edward W. (11 October 2018).
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where anaerobes can thrive), which might have paved way for the
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one with abundant free oxygen molecules — an event known as
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peak centered in the energy-rich green-yellow region of the
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Colorful Worlds: Plants on Other
Planets Might Not Be Green
563:. This coincided with a 300 million year-long global
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lipids in the cell membrane, as well as the discovery of
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CNN Colorscope-When life on Earth began, it was purple
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Pages displaying wikidata descriptions as a fallback
652:created an overall green biosphere all over Earth.
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on the Earth's surface were depleted, and the once-
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575:(which might also have been partly caused by the
354:-motive gradient across the membrane and driving
322:Modern examples of retinal-based photosynthesis
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271:and later green photosynthetic organisms.
125:Artist's impression of Earth in the early
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468:Learn how and when to remove this message
109:Learn how and when to remove this message
535:and started to accumulate, first in the
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330:. Many Haloarchaea contain the retinal
255:and other organisms with chlorophyllic
881:"Was life on the early Earth purple?"
793:International Journal of Astrobiology
480:Microorganisms with purple and green
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406:adding citations to reliable sources
47:adding citations to reliable sources
1049:PBS Eons: When the Earth was purple
523:using chlorophyll, highly reactive
182:were based on the simpler molecule
484:frequently co-exist in stratified
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924:10.1038/scientificamerican0676-38
695:— A family of retinal-containing
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499:that "lived in their shadows" to
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656:Implications for astrobiology
186:rather than the more complex
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823:10.1017/S1473550418000423
417:"Purple Earth hypothesis"
360:anoxygenic photosynthesis
58:"Purple Earth hypothesis"
689:to harvest light energy.
650:terrestrial colonization
205:rather than its current
883:. Astrobiology Magazine
623:long-term endosymbiosis
595:capabilities (both the
561:Great Oxygenation Event
218:Great Oxygenation Event
158:Purple Earth Hypothesis
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362:that does not involve
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1001:10.1089/ast.2017.1729
662:extraterrestrial life
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963:Hartnett, Hilairy E.
611:oxygen minimum zones
567:at beginning of the
402:improve this article
374:Evolutionary history
342:, which carries out
167:, first proposed by
43:improve this article
993:2018AsBio..18..663S
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904:Scientific American
866:2006AAS...209.0605S
815:2018arXiv181005150D
774:10.1511/2007.65.224
674:Microbial rhodopsin
581:atmospheric methane
573:Huronian glaciation
553:reducing atmosphere
517:bacteriochlorophyll
505:blue light spectrum
227:Retinal-containing
222:Huronian glaciation
172:Shiladitya DasSarma
169:molecular biologist
762:American Scientist
758:"Extreme Microbes"
549:chemical compounds
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36:verification
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720:Proterozoic
687:Haloarchaea
683:proton pump
642:green algae
633:to evolve.
593:antioxident
569:Proterozoic
328:Haloarchaea
249:green algae
192:chlorophyll
180:Early Earth
150:Haloarchaea
131:hydrosphere
99:August 2023
1063:Categories
984:1705.05791
806:1810.05150
768:(3): 224.
740:References
708:Halorubrum
644:and early
631:eukaryotes
541:atmosphere
497:eubacteria
458:April 2024
428:newspapers
332:derivative
261:isoprenoid
257:organelles
165:hypothesis
69:newspapers
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724:turquoise
699:found in
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577:oxidative
557:oxidizing
529:byproduct
488:known as
338:in their
303:July 2023
199:biosphere
188:porphyrin
1027:29727196
940:24950370
887:28 March
730:Red edge
685:used by
668:See also
608:deep sea
545:reducing
525:dioxygen
486:colonies
346:-driven
334:protein
316:archaeal
275:Evidence
265:archaeal
207:greenish
203:purplish
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989:Bibcode
912:Bibcode
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860:: 901.
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597:aerobic
565:ice age
442:scholar
241:magenta
211:Archean
201:appear
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190:-based
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146:culture
144:Purple
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