Yuk L. Yung
Yuk L. Yung
In Memoriam - 1946-2026
Yuk L. Yung, professor of planetary science and Jet Propulsion Laboratory (JPL) senior research scientist, passed away on March 16, 2026, after a brief illness. He was 79.
Professor Yung's research interest consisted of six major overlapping areas: planetary atmospheres, planetary evolution, atmospheric chemistry, atmospheric radiation, astrobiology and global change, with a strong emphasis on interaction and synergy among modeling, laboratory experiments and field observations, often in collaboration with colleagues at Caltech and the Jet Propulsion Laboratory (JPL).
Planetary scientists study the earth, planets in our solar system and extra-solar planets, as a matter of intellectual curiosity, as a window on the origin and evolution of the solar system, and also as laboratories in which theories and models of our own atmosphere can be tested. Professors Yung's research has covered the planets Mars, Venus, Jupiter, Uranus and Neptune, the moons Io (Jupiter), Ganymede (Jupiter), Callisto (Jupiter), Titan (Saturn) and Triton (Neptune), as well as extra-solar planets such as HD209458b. He has studied a wide variety of gases in these atmospheres, including H2, O2, O3, N2, N2O, H2O, HDO, CO, CO2, halogens, methane and higher hydrocarbons, ammonia, sulfur compounds and aerosols.
In his work on planetary observations, Professor Yung collaborated with spacecraft teams. He was a co-investigator on the Ultraviolet Imaging Spectrometer (UVIS) Experiment on the Cassini mission to Saturn (1987-present), the Orbital Carbon Observatory-2 (OCO-2), a project to map CO2 concentrations for the Earth (launch 2014). He was an Interdisciplinary Scientist for Venus Express, an European Space Agency mission (2005-present).
Atmospheric Radiation: Theoretical Basis with R.M. Goody (Oxford University Press 1989) and Photochemistry of Planetary Atmospheres with W. B. DeMore (Oxford University Press 1999).He was the author or co-author of over 270 peer-reviewed scientific articles.
Additional Links
Publications
The papers of Professor Yung are available in
https://web.gps.caltech.edu/~yly/yly_mac/ReprintsYLY/
Highlights are briefly described as follows. The paper number refers to the numbering in the Bibliography, available in
http://web.gps.caltech.edu/~yly/yly_mac/ReprintsYLY_CV_Biblio/Biblio_Yung.pdf
The chemistry of the atmosphere of Mars is like the hydrogen atom of the solar system. It is, to paraphrase Einstein, "as simple as possible but not simpler". See model of the photochemistry and evolution of the Martian atmosphere (papers 11, 65 and 89).
H. Nair, M. Allen, A.D. Anbar, Y.L. Yung, and R.T. Clancy, 1994, A photochemical model of the Martian atmosphere. Icarus, 111, 124-150.
Venus is our sister planet. There is great similarity between the catalytic chemistry of Venus and Earth. See model of the photochemistry of chlorine on Venus (papers 2 and 39). Note that paper 2 was published a year before the classic Molina and Rowland 1974 paper on the effects of chlorine in the terrestrial atmosphere, for which they were awarded the Nobel Prize in Chemistry in 1995.
Y.L. Yung and W.B. DeMore, 1982, Photochemistry of the stratosphere of Venus: Implications for atmospheric evolution. Icarus, 51, 199-247.
The chemistry of the atmosphere of the outer solar system is characterized by organic synthesis and production of aerosols known as tholins. See comprehensive model of the photochemistry and evolution of the atmosphere of Titan (papers 35, 49 and 54) and comprehensive model of the photochemistry of the atmosphere of Jupiter (paper 96).
Y.L. Yung, M. Allen, and J.P. Pinto, 1984, Photochemistry of the atmosphere of Titan: Comparison between model and observations. Astrophys. J. Suppl., 55, 465-506.
G.R. Gladstone, M. Allen, and Y.L. Yung, 1996, Hydrocarbon photochemistry in the upper atmosphere of Jupiter. Icarus, 119, 1-52.
The chemistry of the atmosphere of the earth offers intriguing comparisons to the planets. The bromine chemistry on earth is similar to the chlorine chemistry on Venus. The hydrogen chemistry in the terrestrial mesosphere resembles that on Mars. Detailed model of the photochemistry of bromine in the Earth's atmosphere (papers 6 and 29). Bromine is one of the four major catalysts for controlling stratospheric ozone, the other three being chlorine, odd hydrogen and odd nitrogen.
Y.L. Yung J.P. Pinto, R.T. Watson, and S.P. Sander, 1980, Atmospheric bromine and ozone perturbations in the lower stratosphere. J. Atmos. Sci., 37, 339-353.
Detailed model of the photochemistry of the terrestrial mesosphere is described in papers 36 and 53.
M. Allen, Y.L. Yung, and J. Waters, 1981, Vertical transport and photochemistry in the terrestrial mesosphere and lower thermosphere (50-120 km). J. Geophys. Res., 86, 3617-3627.
Dr. Yung's fundamental contributions on radiative transfer and photochemical processes of the atmospheres of extrasolar planets have produced numerous new research areas. In collaboration with his former postdoc Dr. Giovanna Tinetti and former student Dr. Liang Mao-Chang, Dr. Yung's team reported the first conclusive discovery of the presence of water vapor in the atmosphere of the planet HD189733b, 63 light-years away, in the constellation Vulpecula. This is a significant step towards the search for life beyond our Solar System, and the first step towards demonstrating that we are not alone in the universe.
Tinetti, G., A. Vidal-Madjar, M. C. Liang, J. P. Beaulieu, Y. Yung, S. Carey, R. J. Barber, J. Tennyson, I. Ribas, N. Allard, G. E. Ballester, D. K. Sing, and F. Selsis, 2007， "Water vapour in the atmosphere of a transiting extrasolar planet." Nature, 448, 169-171.
Global warming due to relatively small concentrations (a few hundred parts per million) of greenhouse gases such as CO2 is already affecting the climate. The apparently inexorable melting of the polar ice caps and a possible but counter-intuitive mini ice age in the northern hemisphere are constantly in the news and even in the cinema. Planetary science, and in particular the understanding of the delicate planetary atmospheres, have been recognized as academic subjects of very great importance and a critical issue for the future of mankind. Professor Yung pioneered the study of radiation and chemistry in the terrestrial atmosphere, with emphasis on the human impact on climate change. A list of significant papers follows. See this paper that points out the greenhouse effect due to the increase of methane, nitrous oxide and stratospheric water vapor in the Earth's atmosphere (paper 14).
W.C. Wang, Y.L. Yung, A.A. Lacis, T. Mo, and J.E. Hansen, 1976, Greenhouse effects due to man-made perturbations of trace gases. Science, 194, 685-690.
An innovative three-band technique for high-precision remote sensing of CO2 from a space platform was proposed in paper 133. This is the theoretical basis for the NASA OCO-2 mission to be launched in 2013.
Z. M. Kuang, J. Margolis, G. Toon, D. Crisp, and Y. L. Yung， 2002. "Spaceborne Measurements of Atmospheric CO2 by High-resolution NIR Spectrometry of Reflected Sunlight: An Introductory Study." Geophysical Research Letters 29(15): art. no.-1716.
The potential environmental problem of a hydrogen economy is discussed in paper 150.
T. K. Tromp, R. L. Shia, M. Allen, and Y. L. Yung, 2003, Potential environmental impact of a hydrogen economy on the stratosphere, Science 300, 1740-1742.
A novel chemical mechanism, photolysis induced isotopic fractionation effect (PHIFE) is first applied to the isotopic fractionation in stratospheric N2O (papers 108, 138), and has other applications (paper 188).
Y.L. Yung and C.E. Miller, 1997, Isotopic fractionation of stratospheric nitrous oxide. Science, 278, 1778-1780.
M. C. Liang, G. A. Blake, B. R. Lewis and Y. L. Yung, Y. L. (2007). "Oxygen Isotopic of carbon dioxide in the Middle Atmosphere." Proceedings of the National Academy of Sciences of the United States of America, 104, doi/10.1073/pnas.0610009104.