David Catling

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David C. Catling is a Professor in Earth and Space Sciences at the University of Washington. He is a 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 participated in NASA's Mars exploration program [1] and contributed research to help find life elsewhere in the solar system and on planets orbiting other stars. [2] [3] He is also known for his work on the evolution of Earth's atmosphere and biosphere, [4] including how Earth's atmosphere became rich in oxygen, [5] allowing complex life to evolve, [6] [7] and conditions conducive to the origin of life. [8] [9] [10]

Contents

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's Ames Research Center from 1995-2001, he became a professor at the University of Washington in 2001. Since 2012, he has been a full professor at the University of Washington. in 2023, he was elected a 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's atmosphere, Catling is known for a theory explaining how the Earth's crust accumulated large quantities of oxidized minerals and how the atmosphere became rich in oxygen. [11] Geological records show that oxygen flooded the atmosphere in a Great Oxidation Event (GOE) starting about 2.4 billion years ago, even though bacteria that produced oxygen likely evolved hundreds of millions of years earlier. Catling's theory proposes that biological oxygen was initially used by reactions with chemicals in the environment; gradually, however, Earth'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'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– a powerful reducing agent -caused Earth to oxidize and reach the GOE tipping point. [12] Measurements of atmospheric xenon in ancient seawater trapped inside old rocks, published since the 2010s, supports the theory: Earth's atmospheric xenon and its lighter isotopes were most plausibly lost by being dragged out to space by vigorously escaping hydrogen. [13]

Other studies about Earth's atmospheric oxygen have considered its second increase around 600 million years ago acted as a precursor to the rise of animal life. Catling proposed looking at oxygen-sensitive variations in stable 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. [14] [15]

Catling also contributed to the first measurements of Earth's atmospheric thickness billions of years ago. He helped pioneer two techniques: using fossil raindrop imprints to set an upper limit on air density, which was applied to fossil imprints from 2.7 billion years ago, [16] [17] 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. [18] [19]

Catling has also researched the evolution of the atmosphere and surface of Mars. [20] 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. [21] Since then, the discovery of salts and clays from former lakebeds has been a key success of missions to Mars by NASA and ESA. Catling was on the Science Team for NASA'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 [22] and the first measurement of soluble salts in martian soil, including the soil pH. [23] 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 super cool and never crystallize. [24] 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's moon Europa, and Saturn's moon Enceladus.

In the field of planetary atmospheres, David Catling and Tyler Robinson 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') occurs a pressure of about 0.1 bar on Earth, Titan, Jupiter, Saturn, Uranus, and Neptune. This level is 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. [25] They propose that pressure around 0.1 bar could be a fairly general rule for planets with stratospheric temperature inversions. This rule could constrain the atmospheric structure of exoplanets and hence their surface temperature and habitability.

Work by Catling and his students is also the first to accurately quantify the thermodynamic disequilibrium in planetary atmospheres of the Solar System, which has been proposed as a means to look for life remotely. [2] [26] [27]

Works

David Catling has authored over 150 scientific articles or book chapters. He is the author of the following books:

Related Research Articles

<span class="mw-page-title-main">Terraforming</span> Hypothetical planetary engineering process

Terraforming or terraformation ("Earth-shaping") is the hypothetical process of deliberately modifying the atmosphere, temperature, surface topography or ecology of a planet, moon, or other body to be similar to the environment of Earth to make it habitable for humans to live on.

The Hadean is the first and oldest of the four known geologic eons of Earth's history, starting with the planet's formation about 4.54 Bya, now defined as Mya set by the age of the oldest solid material in the Solar System found in some meteorites about 4.567 billion years old. The supposed interplanetary collision that created the Moon occurred early in this eon. The Hadean ended 4.031 billion years ago and was succeeded by the Archean eon, with the Late Heavy Bombardment hypothesized to have occurred at the Hadean-Archean boundary.

<span class="mw-page-title-main">Life on Mars</span> Scientific assessments on the microbial habitability of Mars

The possibility of life on Mars is a subject of interest in astrobiology due to the planet's proximity and similarities to Earth. To date, no proof of past or present life has been found on Mars. Cumulative evidence suggests that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms, but habitable conditions do not necessarily indicate life.

<span class="mw-page-title-main">Habitable zone</span> Orbits where planets may have liquid surface water

In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the HZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the HZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence.

A biosignature is any substance – such as an element, isotope, molecule, or phenomenon – that provides scientific evidence of past or present life on a planet. Measurable attributes of life include its complex physical or chemical structures, its use of free energy, and the production of biomass and wastes.

The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would be only 70 percent as intense during that epoch as it is during the modern epoch. The paradox is this: with the young Sun's output at only 70 percent of its current output, early Earth would be expected to be completely frozen, but early Earth seems to have had liquid water and supported life.

Atmospheric escape is the loss of planetary atmospheric gases to outer space. A number of different mechanisms can be responsible for atmospheric escape; these processes can be divided into thermal escape, non-thermal escape, and impact erosion. The relative importance of each loss process depends on the planet's escape velocity, its atmosphere composition, and its distance from its star. Escape occurs when molecular kinetic energy overcomes gravitational energy; in other words, a molecule can escape when it is moving faster than the escape velocity of its planet. Categorizing the rate of atmospheric escape in exoplanets is necessary to determining whether an atmosphere persists, and so the exoplanet's habitability and likelihood of life.

<span class="mw-page-title-main">Great Oxidation Event</span> Paleoproterozoic surge in atmospheric oxygen

The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, was a time interval during the Early Earth's Paleoproterozoic era when the Earth's atmosphere and the shallow ocean first experienced a rise in the concentration of oxygen. This began approximately 2.460–2.426 Ga (billion years) ago during the Siderian period and ended approximately 2.060 Ga ago during the Rhyacian. Geological, isotopic, and chemical evidence suggests that biologically produced molecular oxygen (dioxygen or O2) started to accumulate in Earth's atmosphere and changed it from a weakly reducing atmosphere practically devoid of oxygen into an oxidizing one containing abundant free oxygen, with oxygen levels being as high as 10% of their present atmospheric level by the end of the GOE.

A runaway greenhouse effect will occur when a planet's atmosphere contains greenhouse gas in an amount sufficient to block thermal radiation from leaving the planet, preventing the planet from cooling and from having liquid water on its surface. A runaway version of the greenhouse effect can be defined by a limit on a planet's outgoing longwave radiation which is asymptotically reached due to higher surface temperatures evaporating water into the atmosphere, increasing its optical depth. This positive feedback means the planet cannot cool down through longwave radiation and continues to heat up until it can radiate outside of the absorption bands of the water vapour.

The anti-greenhouse effect is a process that occurs when energy from a celestial object's sun is absorbed or scattered by the object's upper atmosphere, preventing that energy from reaching the surface, which results in surface cooling – the opposite of the greenhouse effect. In an ideal case where the upper atmosphere absorbs all sunlight and is nearly transparent to infrared (heat) energy from the surface, the surface temperature would be reduced by 16%, which is a significant amount of cooling.

<span class="mw-page-title-main">Origin of water on Earth</span> Hypotheses for the possible sources of the water on Earth

The origin of water on Earth is the subject of a body of research in the fields of planetary science, astronomy, and astrobiology. Earth is unique among the rocky planets in the Solar System in having oceans of liquid water on its surface. Liquid water, which is necessary for all known forms of life, continues to exist on the surface of Earth because the planet is at a far enough distance from the Sun that it does not lose its water, but not so far that low temperatures cause all water on the planet to freeze.

<span class="mw-page-title-main">Atmosphere of Mars</span> Layer of gases surrounding the planet Mars

The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.85%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and noble gases. The atmosphere of Mars is much thinner and colder than Earth's having a max density 20g/m3 with a temperature generally below zero down to -60 Celsius. The average surface pressure is about 610 pascals (0.088 psi) which is less than 1% of the Earth's value.

<span class="mw-page-title-main">Atmosphere of Venus</span> Gas layer surrounding Venus

The atmosphere of Venus is the very dense layer of gasses surrounding the planet Venus. Venus's atmosphere is composed of 96.5% carbon dioxide and 3.5% nitrogen, with other chemical compounds present only in trace amounts. It is much denser and hotter than that of Earth; the temperature at the surface is 740 K, and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) under water on Earth. The atmosphere of Venus supports decks of opaque clouds of sulfuric acid that cover the entire planet, making optical Earth-based and orbital observation of the surface impossible. Information about surface topography has been obtained exclusively by radar imaging.

<span class="mw-page-title-main">Extraterrestrial atmosphere</span> Area of astronomical research

The study of extraterrestrial atmospheres is an active field of research, both as an aspect of astronomy and to gain insight into Earth's atmosphere. In addition to Earth, many of the other astronomical objects in the Solar System have atmospheres. These include all the gas giants, as well as Mars, Venus and Titan. Several moons and other bodies also have atmospheres, as do comets and the Sun. There is evidence that extrasolar planets can have an atmosphere. Comparisons of these atmospheres to one another and to Earth's atmosphere broaden our basic understanding of atmospheric processes such as the greenhouse effect, aerosol and cloud physics, and atmospheric chemistry and dynamics.

A paleoatmosphere is an atmosphere, particularly that of Earth, at some unspecified time in the geological past.

<span class="mw-page-title-main">Carbonate–silicate cycle</span> Geochemical transformation of silicate rocks

The carbonate–silicate geochemical cycle, also known as the inorganic carbon cycle, describes the long-term transformation of silicate rocks to carbonate rocks by weathering and sedimentation, and the transformation of carbonate rocks back into silicate rocks by metamorphism and volcanism. Carbon dioxide is removed from the atmosphere during burial of weathered minerals and returned to the atmosphere through volcanism. On million-year time scales, the carbonate-silicate cycle is a key factor in controlling Earth's climate because it regulates carbon dioxide levels and therefore global temperature.

<span class="mw-page-title-main">Planetary surface</span> Where the material of a planetary masss outer crust contacts its atmosphere or outer space

A planetary surface is where the solid or liquid material of certain types of astronomical objects contacts the atmosphere or outer space. Planetary surfaces are found on solid objects of planetary mass, including terrestrial planets, dwarf planets, natural satellites, planetesimals and many other small Solar System bodies (SSSBs). The study of planetary surfaces is a field of planetary geology known as surface geology, but also a focus on a number of fields including planetary cartography, topography, geomorphology, atmospheric sciences, and astronomy. Land is the term given to non-liquid planetary surfaces. The term landing is used to describe the collision of an object with a planetary surface and is usually at a velocity in which the object can remain intact and remain attached.

Mars habitability analogue environments on Earth are environments that share potentially relevant astrobiological conditions with Mars. These include sites that are analogues of potential subsurface habitats, and deep subsurface habitats.

<span class="mw-page-title-main">Prebiotic atmosphere</span>

The prebiotic atmosphere is the second atmosphere present on Earth before today's biotic, oxygen-rich third atmosphere, and after the first atmosphere of Earth's formation. The formation of the Earth, roughly 4.5 billion years ago, involved multiple collisions and coalescence of planetary embryos. This was followed by a <100 million year period on Earth where a magma ocean was present, the atmosphere was mainly steam, and surface temperatures reached up to 8,000 K (14,000 °F). Earth's surface then cooled and the atmosphere stabilized, establishing the prebiotic atmosphere. The environmental conditions during this time period were quite different from today: the Sun was ~30% dimmer overall yet brighter at ultraviolet and x-ray wavelengths, there was a liquid ocean, it is unknown if there were continents but oceanic islands were likely, Earth's interior chemistry was different, and there was a larger flux of impactors hitting Earth's surface.

Xenon isotope geochemistry uses the abundance of xenon (Xe) isotopes and total xenon to investigate how Xe has been generated, transported, fractionated, and distributed in planetary systems. Xe has nine stable or very long-lived isotopes. Radiogenic 129Xe and fissiogenic 131,132,134,136Xe isotopes are of special interest in geochemical research. The radiogenic and fissiogenic properties can be used in deciphering the early chronology of Earth. Elemental Xe in the atmosphere is depleted and isotopically enriched in heavier isotopes relative to estimated solar abundances. The depletion and heavy isotopic enrichment can be explained by hydrodynamic escape to space that occurred in Earth's early atmosphere. Differences in the Xe isotope distribution between the deep mantle, shallower Mid-ocean Ridge Basalts (MORBs), and the atmosphere can be used to deduce Earth's history of formation and differentiation of the solid Earth into layers.

References

  1. ↑ Shapiro, Nina (April 2015). "As a New Space Race Heats Up, Mars Beckons Once Again". Seattle Weekly. Archived from the original on 2016-08-22. Retrieved 2016-08-21.
  2. 1 2 Krissansen-Totton, J.; Bergsman, D. S.; Catling, D. C. (2016). "On detecting biospheres from chemical disequilibrium in planetary atmospheres". Astrobiology. 16 (1): 39–67. arXiv: 1503.08249 . Bibcode:2016AsBio..16...39K. doi:10.1089/ast.2015.1327. PMID   26789355. S2CID   26959254.
  3. ↑ Krissansen-Totton, J.; Schwieterman, E.; Charnay, B.; Arney, G.; Robinson, T. D.; Meadows, V.; Catling, D. C. (2016). "Is the Pale Blue Dot unique? Optimized photometric bands for identifying Earth-like planets". Astrophysical Journal. 817 (1): 31. arXiv: 1512.00502 . Bibcode:2016ApJ...817...31K. doi: 10.3847/0004-637X/817/1/31 . S2CID   119211858.
  4. ↑ Catlng, David C.; Zahnle, Kevin J. (2020). "The Archean Atmosphere". Science Advances. 6 (9): eaax1420. Bibcode:2020SciA....6.1420C. doi:10.1126/sciadv.aax1420. PMC   7043912 . PMID   32133393 . Retrieved 5 August 2022.
  5. ↑ Catling, D. C. (2014). "The Great Oxidation Event Transition". In Holland, H. D.; Turekian, K. K. (eds.). Treatise on Geochemistry (Second ed.). Amsterdam: Elsevier. pp. 177–195. doi:10.1016/B978-0-08-095975-7.01307-3. ISBN   9780080983004.
  6. ↑ Catling, D. C.; Glein, C. R.; Zahnle, K. J.; McKay, C. P. (June 2005). "Why O2 is required by complex life on habitable planets and the concept of planetary "oxygenation time". Astrobiology. 5 (3): 415–438. Bibcode:2005AsBio...5..415C. doi:10.1089/ast.2005.5.415. PMID   15941384. S2CID   24861353.
  7. ↑ Dorminey, Bruce (2012). "Why E.T. Would Also Breathe Oxygen". Forbes Magazine. Retrieved 2016-08-21.
  8. ↑ Anderson, Paul Scott. "Did phosphorus-rich lakes help kickstart life on Earth?". EarthSky. EarthSky Communications Inc. Retrieved 5 August 2022.
  9. ↑ Toner, Jonathan D.; Catling, David C. (2019). "Alkaline lake settings for concentrated prebiotic cyanide and the origin of life". Geochimica et Cosmochimica Acta. 260: 124–132. Bibcode:2019GeCoA.260..124T. doi: 10.1016/j.gca.2019.06.031 . S2CID   198356131.
  10. ↑ Zahnle, Kevin J.; Lupu, Roxana; Catling, David C.; Wogan, N. (2020). "Creation and evolution of impact-generated reduced atmospheres of early Earth". Planetary Science Journal. 1 (1): 11. arXiv: 2001.00095 . Bibcode:2020PSJ.....1...11Z. doi: 10.3847/psj/ab7e2c . S2CID   209531939.
  11. ↑ Catling, D. C.; Zahnle, K. J.; McKay, C. P. (2001). "Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth". Science. 293 (5531): 839–843. Bibcode:2001Sci...293..839C. CiteSeerX   10.1.1.562.2763 . doi:10.1126/science.1061976. PMID   11486082. S2CID   37386726.
  12. ↑ Zahnle, K. J.; Catling, D. C. "Waiting for oxygen". In Shaw, G. H. (ed.). Special Paper 504: Earth's Early Atmosphere and Surface Environment. Geological Society of America. pp. 37–48.
  13. ↑ Zahnle, Kevin J.; Gacesa, Mark; Catling, David C. (2019). "Strange messenger: A new history of hydrogen on Earth as told by xenon". Geochimica et Cosmochimica Acta. 244 (1): 56–85. arXiv: 1809.06960 . Bibcode:2019GeCoA.244...56Z. doi:10.1016/j.gca.2018.09.017. S2CID   119079927 . Retrieved 5 August 2022.
  14. ↑ Pogge von Strandmann, P.; Stüeken, E. E.; Elliott, T.; Poulton, S. W.; Dehler, C. M.; Canfield, D. E.; Catling, D. C. (2015). "Selenium isotope evidence for progressive oxidation of the Neoproterozoic biosphere". Nature Communications. 6: 10157. Bibcode:2015NatCo...610157P. doi:10.1038/ncomms10157. PMC   4703861 . PMID   26679529.
  15. ↑ "Oxygen provided breath of life that allowed animals to evolve". Washington.edu. Retrieved January 31, 2016.
  16. ↑ Som, S. M.; Catling, D. C.; Harnmeijer, J. P.; Polivka, P. M.; Buick, R. (2012). "Air density 2.7 billion years ago limited to less than twice modern levels by fossil raindrop imprints". Nature. 484 (7394): 359–362. Bibcode:2012Natur.484..359S. doi:10.1038/nature10890. PMID   22456703. S2CID   4410348.
  17. ↑ Marder, Jenny (2012). "What a Baking Pan and Hairspray Taught Us About Earth's Ancient Atmosphere". PBS Newshour. Retrieved 2016-08-21.
  18. ↑ Som, S. M.; Buick, R.; Hagadorn, J. W.; Blake, T. S.; Perrault, J. M.; Harnmeijer, J. P.; Catling, D. C. (2012). "Earth's air pressure 2.7 billion years ago constrained to less than half of modern levels". Nature Geoscience. 9 (6): 448–451. Bibcode:2016NatGe...9..448S. doi:10.1038/ngeo2713. S2CID   4662435.
  19. ↑ "The curious lightness of an early atmosphere". The Economist. Vol. 419, no. 8989. May 14–20, 2012. pp. 69–70.
  20. ↑ Catling, David C. (2014-08-04). "Mars Atmosphere: History and Surface Interactions". In Spohn, T.; Breuer, D.; Johnson, T. V. (eds.). Encyclopedia of the Solar System (Third ed.). Amsterdam: Elsevier. pp. 343–357. ISBN   9780124158450.
  21. ↑ Catling, D. C. (1999). "A chemical model for evaporites on early Mars: Possible sedimentary tracers of the early climate and implications for exploration". Journal of Geophysical Research. 104 (E7): 16, 453–16, 470. Bibcode:1999JGR...10416453C. doi: 10.1029/1998JE001020 . S2CID   129783260.
  22. ↑ Smith, P. H.; Tamppari, L.; Arvidson, R. E.; Bass, D. S.; Blaney, D.; Boynton, W. V.; Carswell, A.; Catling, D. C.; et al. (2009). "H2O at the Phoenix landing site". Science. 325 (5936): 58–61. Bibcode:2009Sci...325...58S. doi:10.1126/science.1172339. PMID   19574383. S2CID   206519214.
  23. ↑ Hecht, M. H.; Kounaves, S. P.; Quinn, R. C.; West, S. J.; Young, S. M. M.; Ming, D. W.; Catling, D. C.; Clark, B. C.; Boynton, W. V.; Hoffman, J.; DeFlores, L. P.; Gospodinova, K.; Kapit, J.; Smith, P. H. (2009). "Detection of perchlorate and soluble chemistry of martian soil: Findings from the Phoenix Mars Lander". Science. 325 (5936): 64–67. Bibcode:2009Sci...325...64H. doi:10.1126/science.1172466. PMID   19574385. S2CID   24299495.
  24. ↑ Toner, J. D.; Catling, D. C.; Light, B. (2014). "The formation of supercooled brines, viscous liquids, and low-temperature glasses on Mars". Icarus. 233: 36–47. Bibcode:2014Icar..233...36T. doi:10.1016/j.icarus.2014.01.018.
  25. ↑ Robinson, T. D.; Catling, D. C. (2014). "Common 0.1 bar tropopause in thick atmospheres set by pressure-dependent infrared transparency". Nature Geoscience. 7 (1): 12–15. arXiv: 1312.6859 . Bibcode:2014NatGe...7...12R. doi:10.1038/NGEO2020. S2CID   73657868.
  26. ↑ Hickey, Hanna. "A new 'atmospheric disequilibrium' could help detect life on other planets". UW News. University of Washington. Retrieved 5 August 2022.
  27. ↑ Krissansen-Totton, Joshua; Olson, Stephanie; Catling, David C. (2018). "Disequilibrium biosignatures over Earth history and implications for detecting exoplanet life". Science Advances. 4 (1): eaao5747. arXiv: 1801.08211 . Bibcode:2018SciA....4.5747K. doi:10.1126/sciadv.aao5747. PMC   5787383 . PMID   29387792. S2CID   13702047.
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