Xi Zhang received the 2019 Ronald Greeley Early Career Award in Planetary Sciences at AGU’s Fall Meeting 2019, held 9–13 December in San Francisco, Calif. The award recognizes “significant early career contributions to planetary science.”  

Xi Zhang received his Ph.D. in planetary sciences from California Institute of Technology in 2013. He is one of the few scientists whose research covers many subfields in planetary atmospheres, including remote sensing, fluid dynamics, chemistry, haze and cloud formation, and radiative transfer. Xi’s work revolutionized our understanding of the roles of aerosols in planetary atmospheres in many aspects. Xi’s proposal on the feedback of sulfur aerosols on gas chemistry is the leading theory to explain Venus Express’s observations of sulfur oxides. From Cassini data, Xi derived maps of temperature, chemical species, and aerosols in Jupiter’s stratosphere and identified the role of aerosols in the energy budget on Jupiter. Xi proposed an explanation for the unexpected cold atmosphere of Pluto observed by the New Horizons mission. He found out that hazes in Pluto’s atmosphere, instead of gases, dominate the radiative cooling as well as the heating. This discovery led to a paradigm shift in our understanding of the atmospheric energy balance of the new “cold and hazy” regime that also includes Neptune’s moon Triton and Saturn’s moon Titan. Xi’s work has implications for the haze and cloud formation on exoplanets and its impact on observed spectra and planetary evolution of low-mass planets, as well as on developing the next-generation three-dimensional general circulation models of the cloudy atmospheres on giant planets, exoplanets, and brown dwarfs. His contributions overall have been both wide and deep, revolutionizing our understanding of planetary climate.

—Yuk Yung, California Institute of Technology, Pasadena

I am deeply honored to be the recipient of the Ronald Greeley Early Career Award this year. I thank the award committee for this recognition. Just like Ron, I enjoy working in many diverse fields. I hope my research will be as wide and as deep as his is. I would like to thank my nominator and Ph.D. advisor, Yuk Yung, for his continuous support and important guidance from his deep thoughts on Eastern and Western cultures. I would also like to thank my postdoc advisor, Adam Showman, who is not only a mentor but also a good friend. Thanks to all the colleagues and collaborators who have supported and encouraged me in these years, especially Mark Allen, Bob West, Darrell Strobel, and Julie Moses. I would like to thank my undergraduate advisor, Zuo Xiao, at Peking University for his tremendous help in my early career. Thanks to my undergrads, Ph.D. students, postdocs, and visiting scholars at University of California, Santa Cruz. Finally, I would also like to take this opportunity to acknowledge all the support from my friends and my family. In particular, I dedicate this great honor to my wife, Yunwen Duan, for her unwavering love, support, and belief in me. I owe her everything. —Xi Zhang, University of California, Santa Cruz