'''David C. Catling''' is a Professor in Earth and Space Sciences at at the [[University of Washington]]. He is a [[planetary science|planetary scientist]] and [[astrobiologist]] whose research focuses on understanding the differences between the evolution of planets, their atmospheres, and their potential for life. He has been activeparticipated in [[NASA |NASA’s]] 's [[Exploration of Mars|Mars exploration]] program <ref>{{Cite andweb|url=http://archive.seattleweekly.com/home/957816-129/a-would-be-martian-signs-up-to|title=As hasa New Space Race Heats Up, Mars Beckons Once Again|last=Shapiro|first=Nina|date=April 2015|website=Seattle Weekly|access-date=2016-08-21|archive-url=https://web.archive.org/web/20160822063310/http://archive.seattleweekly.com/home/957816-129/a-would-be-martian-signs-up-to|archive-date=2016-08-22|url-status=dead}}</ref> and contributed research to help find life elsewhere in the solar system and on planets orbiting other stars.<ref name=krissansentotton2016>{{cite journal|last1=Krissansen-Totton|first1=J.|last2=Bergsman|first2=D. S.|last3=Catling|first3=D. C.|title=On detecting biospheres from chemical disequilibrium in planetary atmospheres|journal=Astrobiology|date=2016|volume=16 |issue=1|pages=39–67|doi=10.1089/ast.2015.1327 |bibcode=2016AsBio..16...39K|pmid=26789355|arxiv=1503.08249|s2cid=26959254 }}</ref><ref>{{cite journal|last1=Krissansen-Totton|first1=J.|last2=Schwieterman|first2=E.|last3=Charnay|first3=B.|last4=Arney|first4=G.|last5=Robinson|first5=T. D.|last6=Meadows|first6=V.|last7=Catling|first7=D. C.|title=Is the Pale Blue Dot unique? Optimized photometric bands for identifying Earth-like planets|journal=Astrophysical Journal|date=2016|volume=817 |issue=1|page=31|doi=10.3847/0004-637X/817/1/31 |arxiv=1512.00502|bibcode=2016ApJ...817...31K|s2cid=119211858 |doi-access=free }}</ref> He is also known for his work on the evolution of Earth’sEarth's atmosphere and biosphere, <ref>{{cite particularlyjournal |last1=Catlng |first1=David C. |last2=Zahnle |first2=Kevin J. |title=The Archean Atmosphere |journal=Science Advances |date=2020 |volume=6 |issue=9 |page=eaax1420 |doi=10.1126/sciadv.aax1420 |pmid=32133393 |pmc=7043912 |bibcode=2020SciA....6.1420C |url=http://dx.doi.org/10.1126/sciadv.aax1420 |access-date=5 August 2022}}</ref> including how Earth’sEarth's atmosphere became rich in oxygen ,<ref>{{cite book|last1=Catling|first1=D. C.|editor1-last=Holland|editor1-first=H. D.|editor2-last=Turekian|editor2-first=K. K.|title=Treatise on Geochemistry|date=2014|publisher= [[Elsevier ]]|location=Amsterdam|pages=177–195|edition=Second|chapter=The Great Oxidation Event Transition |doi=10.1016/B978-0-08-095975-7.01307-3|isbn=9780080983004}}</ref> and allowedallowing complex life to evolve .,<ref>{{cite journal|last1=Catling|first1=D. C.|last2=Glein|first2=C. R.|last3=Zahnle|first3=K. J.|last4=McKay|first4=C. P. |s2cid=24861353|title=Why O2O<sub>2</sub> is required by complex life on habitable planets and the concept of planetary "oxygenation time|journal=Astrobiology|volume=5 |issue=3|pages=415–438 |doi=10.1089/ast.2005.5.415|bibcode=2005AsBio...5..415C|pmid=15941384|date=June 2005}}</ref><ref>{{Cite web|url=https://www.forbes.com/sites/brucedorminey/2012/11/20/why-e-t-would-also-breathe-oxygen/|title=Why E.T. Would Also Breathe Oxygen|last=Dorminey|first=Bruce|date=2012|website=Forbes Magazine|access-date=2016-08-21}}</ref> and conditions conducive to the [[Abiogenesis|origin of life]].<ref>{{cite web |last1=Anderson |first1=Paul Scott |title=Did phosphorus-rich lakes help kickstart life on Earth? |url=https://earthsky.org/earth/phosphate-problem-carbonate-lakes-early-earth-life/ |website=EarthSky |publisher=EarthSky Communications Inc. |access-date=5 August 2022}}</ref><ref>{{cite journal |last1=Toner |first1=Jonathan D. |last2=Catling |first2=David C. |title=Alkaline lake settings for concentrated prebiotic cyanide and the origin of life |journal=Geochimica et Cosmochimica Acta |date=2019 |volume=260 |pages=124–132 |doi=10.1016/j.gca.2019.06.031 |bibcode=2019GeCoA.260..124T |s2cid=198356131 |doi-access=free }}</ref><ref>{{cite journal |last1=Zahnle |first1=Kevin J. |last2=Lupu |first2=Roxana |last3=Catling |first3=David C. |last4=Wogan |first4=N. |title=Creation and evolution of impact-generated reduced atmospheres of early Earth |journal=Planetary Science Journal |date=2020 |volume=1 |issue=1 |page=11 |doi=10.3847/psj/ab7e2c |arxiv=2001.00095 |bibcode=2020PSJ.....1...11Z |s2cid=209531939 |doi-access=free }}</ref> ▼
{{orphan|date=January 2016}}
▲'''David Catling''' is a Professor in Earth and Space Sciences at at the [[University of Washington]]. He is a [[planetary science|planetary scientist]] and [[astrobiologist]] whose research focuses on understanding the differences between the evolution of planets, their atmospheres, and their potential for life. He has been active in [[NASA|NASA’s]] [[Exploration of Mars|Mars exploration]] program and has contributed research to help find life elsewhere in the solar system and on planets orbiting other stars.<ref>{{cite journal|last1=Krissansen-Totton|first1=J.|last2=Bergsman|first2=D. S.|last3=Catling|first3=D. C.|title=On detecting biospheres from chemical disequilibrium in planetary atmospheres|journal=Astrobiology|date=2016|volume=16|pages=39–67|doi=10.1089/ast.2015.1327}}</ref><ref>{{cite journal|last1=Krissansen-Totton|first1=J.|last2=Schwieterman|first2=E.|last3=Charnay|first3=B.|last4=Arney|first4=G.|last5=Robinson|first5=T. D.|last6=Meadows|first6=V.|last7=Catling|first7=D. C.|title=Is the Pale Blue Dot unique? Optimized photometric bands for identifying Earth-like planets|journal=Astrophysical Journal|date=2016|volume=817|page=31|doi=10.3847/0004-637X/817/1/31}}</ref> He is also known for his work on the evolution of Earth’s atmosphere and biosphere, particularly how Earth’s atmosphere became rich in oxygen<ref>{{cite book|last1=Catling|first1=D. C.|editor1-last=Holland|editor1-first=H. D.|editor2-last=Turekian|editor2-first=K. K.|title=Treatise on Geochemistry|date=2014|publisher=Elsevier|location=Amsterdam|pages=177–195|edition=Second|chapter=The Great Oxidation Event Transition}}</ref> and allowed complex life to evolve.<ref>{{cite journal|last1=Catling|first1=D. C.|last2=Glein|first2=C. R.|last3=Zahnle|first3=K. J.|last4=McKay|first4=C. P.|title=Why O2 is required by complex life on habitable planets and the concept of planetary "oxygenation time|journal=Astrobiology|volume=5|pages=415–438}}</ref>
== Biography ==
David Catling completed a D.Phil. in the Department of Atmospheric, Oceanic, and Planetary Physics at the [[University of Oxford]] in 1994. After working as a postdoctoral scholar and then research scientist at NASA’sNASA's [[Ames Research Center]] from 1995-2001, he became a professor at the [[University of Washington]] in 2001. Since 2012, he has been a [[professor|full professor]] at the University of Washington. in 2023, he was elected a [[American Geophysical Union#Fellowships|fellow]] of the [[American Geophysical Union]] (AGU) for “for creative insights into coupling between Earth’s biota and its atmosphere over timescales of billions of years”.
== Research ==
In the area of the evolution of the Earth’sEarth's atmosphere, Catling is known for a theory explaining how the Earth’sEarth's crust accumulated large quantities of oxidized minerals and how the atmosphere became rich in oxygen.<ref>{{cite journal|last1=Catling|first1=D. C.|last2=Zahnle|first2=K. J.|last3=McKay|first3=C. P.|title=Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth|journal=Science|date=2001|volume=293|issue=5531|pages=839–843|doi=10.1126/science.1061976|pmid=11486082|bibcode=2001Sci...293..839C|citeseerx=10.1.1.562.2763|s2cid=37386726 }}</ref> Geological records show that oxygen flooded the atmosphere in a [[Great Oxygenation Event|Great Oxidation Event]] (GOE) starting about 2.4 billion years ago, even though bacteria that produced oxygen likely evolved hundreds of billionsmillions of years earlier. Catling’sCatling's theory proposes that biological oxygen was initially used up as fast as biology produced it by reactions with chemicals in the environment; gradually, however, Earth’sEarth's environment shifted to a tipping point where oxygen flooded the air. [[Atmospheric methane]] is the key part of this theory. Before oxygen was abundant, methane gas could reach concentrations hundreds or thousands of times greater than today’stoday's 1.8 parts per million. Ultraviolet light decomposes methane molecules in the upper atmosphere, causing hydrogen gas to escape into space. Over time, the irreversible [[atmospheric escape]] of hydrogen –hydrogen– a powerful reducing agent - caused Earth to oxidize and reach the GOE tipping point.<ref>{{cite book|last1=Zahnle|first1=K. J.|last2=Catling|first2=D. C.|editor1-last=Shaw|editor1-first=G. H.|title=Special Paper 504: Earth's Early Atmosphere and Surface Environment|publisher=[[Geological Society of America]]|pages=37–48|chapter=Waiting for oxygen}}</ref> Measurements of atmospheric xenon in ancient seawater trapped inside old rocks, published since the 2010s, supports the theory: Earth's atmospheric [[Xenon isotope geochemistry|xenon and its lighter isotopes]] were most plausibly lost by being dragged out to space by vigorously escaping hydrogen.<ref>{{cite journal |last1=Zahnle |first1=Kevin J. |last2=Gacesa |first2=Mark |last3=Catling |first3=David C. |title=Strange messenger: A new history of hydrogen on Earth as told by xenon |journal=Geochimica et Cosmochimica Acta |date=2019 |volume=244 |issue=1 |pages=56–85 |doi=10.1016/j.gca.2018.09.017 |arxiv=1809.06960 |bibcode=2019GeCoA.244...56Z |s2cid=119079927 |url=https://doi.org/10.1016/j.gca.2018.09.017 |access-date=5 August 2022}}</ref>
Other studies about Earth’sEarth's atmospheric oxygen have considered its second increase around 600 million years ago that acted as a precursor to the [[Cambrian explosion|rise of animal life]]. Catling proposed looking at oxygen-sensitive variations in seleniumstable [[isotopes of selenium]] to trace atmospheric and seawater oxygen, and the results of such a study showed that Earth's second increase in oxygen occurred in fits and starts spread over about 100 million years.<ref>{{cite journal|last1=Pogge von Strandmann|first1=P.|last2=Stüeken|first2=E. E.|last3=Elliott|first3=T.|last4=Poulton|first4=S. W.|last5=Dehler|first5=C. M.|last6=Canfield|first6=D. E.|last7=Catling|first7=D. C.|title=Selenium isotope evidence for post-glacialprogressive oxygenationoxidation trends inof the EdiacaranNeoproterozoic oceanbiosphere|journal=Nature Communications|date=2015|volume=6|page=10157|doi=10.1038/ncomes10157ncomms10157|urlpmid=http://www26679529|pmc=4703861|bibcode=2015NatCo.nature.com/ncomms/2015/151218/ncomms10157/full/ncomms10157.html610157P }}</ref><ref name="MyUser_Washington.edu_January_31_2016c">{{cite web |url=http://www.washington.edu/news/2015/12/18/oxygen-provided-breath-of-life-that-allowed-animals-to-evolve/ |title=Oxygen provided breath of life that allowed animals to evolve |newspaper=Washington.edu |access-date= |author= |accessdate= January 31, 2016}}</ref>
Catling also contributed to the first measurementmeasurementsofEarth’sEarth's atmospheric thickness billions of years ago . He helped pioneer atwo technique totechniques: useusing fossil raindrop imprints to set a quantitativean upper limit on air density, which was applied to fossil imprints from 2.7 billion years ago.,<ref>{{cite journal|last1=Som|first1=S. M.|last2=Catling|first2=D. C.|last3=Harnmeijer|first3=J. P.|last4=Polivka|first4=P. M.|last5=Buick|first5=R.|s2cid=4410348|title=Air density 2.7 billion years ago limited to less than twice modern levels by fossil raindrop imprints|journal=Nature|date=2012|volume=484|issue=7394|pages=359–362|doi=10.1038/nature10890|pmid=22456703|bibcode=2012Natur.484..359S}}</ref><ref>{{Cite web|url=https://www.pbs.org/newshour/rundown/what-a-cake-pan-hairspray-taught-us-about-earths-ancient-atmosphere/|title=What a Baking Pan and Hairspray Taught Us About Earth's Ancient Atmosphere|last=Marder|first=Jenny|date=2012|website=PBS Newshour|language=en-US|access-date=2016-08-21}}</ref> and using fossil bubbles in ancient lava flows, which suggests that air pressure 2.7 billion years ago was less than half that of the modern atmosphere.<ref>{{Cite journal|last1=Som|first1=S. M.|last2=Buick|first2=R.|last3=Hagadorn|first3=J. W.|last4=Blake|first4=T. S.|last5=Perrault|first5=J. M.|last6=Harnmeijer|first6=J. P.|last7=Catling|first7=D. C.|s2cid=4662435|date=2012|title=Earth's air pressure 2.7 billion years ago constrained to less than half of modern levels|journal=Nature Geoscience|volume=9|issue=6|pages=448–451|doi=10.1038/ngeo2713|bibcode=2016NatGe...9..448S}}</ref><ref>{{Cite news|date=May 14–20, 2012|title=The curious lightness of an early atmosphere|url=https://www.economist.com/news/science-and-technology/21698640-two-new-studies-suggest-young-earth-may-have-been-even-less-todays|newspaper=The Economist|volume=419|issue=8989|pages=69–70}}</ref>
Catling has also done research onresearched the evolution of the atmosphere and surface of Mars.<ref>{{cite book|last1=Catling|first1=David C.|editor1-last=Spohn|editor1-first=T.|editor2-last=Breuer|editor2-first=D.|editor3-last=Johnson|editor3-first=T. V.|title=Encyclopedia of the Solar System|publisher=Elsevier|location=Amsterdam|isbn=9780124158450|pages=343–357|edition=Third|chapter=Mars Atmosphere: History and Surface Interactions|date=2014-08-04}}</ref>In particular, in the 1990s, he pioneered research on how the types of salts from dried-up lakes or seas on Mars could indicate the past environment and whether Mars was habitable.<ref>{{cite journal|last1=Catling|first1=D. C.|s2cid=129783260|title=A chemical model for evaporites on early Mars: Possible sedimentary tracers of the early climate and implications for exploration|journal=Journal of Geophysical Research|date=1999|volume=104|issue=E7|pages=16,453-16453–16,470|doi=10.1029/1998JE001020|bibcode=1999JGR...10416453C|doi-access=free}}</ref> Since then, the discovery of salts and clays from former lakebeds has been a key success of missions to Mars by NASA and [[European Space Agency|ESA]]. Catling was a member ofon the Science Team for NASA’sNASA's [[Phoenix Lander]] mission, which in 2008 was the first spacecraft to land in the ice-rich high latitudes of Mars. Catling contributed to research that included the first scoops by a lander of water ice from below the surface of Mars<ref>{{cite journal|last1=Smith|first1=P. H.|last2=Tamppari|first2=L.|last3=Arvidson|first3=R. E.|last4=Bass|first4=D. S.|last5=Blaney|first5=D.|author5-link= Diana Blaney |last6=Boynton|first6=W. V.|last7=Carswell|first7=A.|last8=Catling|first8=D. C.|last9=et al.|title=H2O at the Phoenix landing site|journal=Science|date=2009|volume=325|issue=5936|pages=58–61|doi=10.1126/science.1172339|display-authors=etal|pmid=19574383|bibcode=2009Sci...325...58S|s2cid=206519214 }}</ref> and the first measurement of soluble salts in martian soil, including the [[soil pH]].<ref>{{cite journal|last1=Hecht|first1=M. H.|last2=Kounaves|first2=S. P.|last3=Quinn|first3=R. C.|last4=West|first4=S. J.|last5=Young|first5=S. M. M.|last6=Ming|first6=D. W.|last7=Catling|first7=D. C.|last8=Clark|first8=B. C.|last9=Boynton|first9=W. V.|last10=Hoffman|first10=J.|last11=DeFlores|first11=L. P.|last12=Gospodinova|first12=K.|last13=Kapit|first13=J.|last14=Smith|first14=P. H.|s2cid=24299495|title=Detection of perchlorate and soluble chemistry of martian soil: Findings from the Phoenix Mars Lander|journal=Science|date=2009|volume=325|issue=5936|pages=64–67|doi=10.1126/science.1172466|pmid=19574385|bibcode=2009Sci...325...64H}}</ref> In experimental work with Jonathan Toner to examine low -temperature solutions of [[perchlorate]] salts, as found on Mars, Toner and Catling discovered that such solutions supercoolsuper cool and never crystallize.<ref>{{cite journal|last1=Toner|first1=J. D.|last2=Catling|first2=D. C.|last3=Light|first3=B.|title=The formation of supercooled brines, viscous liquids, and low-temperature glasses on Mars|journal=Icarus|date=2014|volume=233|pages=36–47|doi=10.1016/j.icarus.2014.01.018|bibcode=2014Icar..233...36T}}</ref> The perchlorates form glasses ([[amorphous solids]]) around -120 °C. Glasses are known to be far better for preserving microbes and biological molecules than crystalline salts, which could be relevant to the search for [[life on Mars]], Jupiter’sJupiter's moon [[Europa (moon)|Europa]], and Saturn’sSaturn's moon [[Enceladus]].
In the field of planetary atmospheres, David Catling and Tyler Robinson have proposed a general explanation for a curious observation: the minimum air temperature between the [[troposphere]] (the lowest atmospheric layer where temperature declines with altitude) and [[stratosphere]] (where temperature increases with altitude in an '[[Inversion (meteorology)|inversion]]') occurs a pressure of about 0.1 bar on Earth, Titan, Jupiter, Saturn, Uranus, and Neptune. This level is known as the [[tropopause]]. Robinson and Catling used the physics of radiation to explain why the tropopause temperature minimum in these extremely different atmospheres occurs at a common pressure.<ref>{{cite journal|last1=Robinson|first1=T. D.|last2=Catling|first2=D. C.|title=Common 0.1 bar tropopause in thick atmospheres set by pressure-dependent infrared transparency|journal=Nature Geoscience|date=2014|volume=7|issue=1|pages=12–15|doi=10.1038/NGEO2020|arxiv=1312.6859|bibcode=2014NatGe...7...12R|s2cid=73657868 }}</ref> They propose that a tropopause temperature minimumpressure around 0.1 bar could be a fairly general rule for planets with stratospheric temperature inversions. This rule could constrain the atmospheric structure onof exoplanets and hence their surface temperature and habitability.
Work by Catling and his students is also the first to accurately quantityquantify the thermodynamic disequilibrium in planetary atmospheres of the Solar System, which has been proposedas a means to look for life remotely.<ref name=krissansentotton2016 /><ref>{{cite web |last1=Hickey |first1=Hanna |title=A new 'atmospheric disequilibrium' could help detect life on other planets |url=https://www.washington.edu/news/2018/01/24/a-new-atmospheric-disequilibrium-could-help-detect-life-on-other-planets/ |website=UW News |publisher=University of Washington |access-date=5 August 2022}}</ref><ref>{{cite journal |last1=Krissansen-Totton |first1=J.Joshua |last2=BergsmanOlson |first2=D.Stephanie S.|last3=Catling |first3=D.David C. |title=OnDisequilibrium detectingbiosignatures biospheresover fromEarth chemicalhistory disequilibriumand inimplications planetaryfor detecting exoplanet life atmospheres|journal=AstrobiologyScience Advances |date=20162018 |volume=164|pagesissue=39–671 |page=eaao5747 |doi=10.10891126/astsciadv.2015aao5747 |pmid=29387792 |pmc=5787383 |arxiv=1801.08211 |bibcode=2018SciA....4.5747K |s2cid=13702047 |url=https://doi.org/10.1126/sciadv.1327aao5747}}</ref>
==Works==
David Catling has authored over 100150 scientific articles or book chapters. He is the author of the following books:
* Catling, David C. ''Astrobiology: A Very Short Introduction'', Oxford University Press, Oxford, 2013, {{ISBN |0-19-958645-4}}.
* Catling, David C.; [[James Kasting|Kasting, James F.]] ''Atmospheric Evolution on Inhabited and Lifeless Worlds''. Cambridge University Press. Cambridge, 20162017. In press{{ISBN|978-0521844123}}.
==References==
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[[Category:University of Washington faculty]]
[[Category:Fellows of the American Geophysical Union]]
[[Category:Living people]]
[[Category:Astrobiologists]]
[[Category:Year of birth missing (living people)]]
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