An Yin, a UCLA distinguished professor of Earth, planetary and space sciences, died on July 12. He was 64 years old. 

Yin was widely recognized for his profound contributions to the understanding of our planet and others in our solar system. His colleague Mark Harrison said Yin was the world’s single greatest authority on the Indo-Asian collision, the geological event that formed the Himalayas and Tibetan Plateau.

“Our entire community has suffered an immense loss,” said Harrison, a UCLA distinguished professor of Earth, planetary and space sciences. “An had a luminous and jocular personality beneath which lay an extraordinarily incisive and original mind.

“The sudden loss of this intellectual giant will be felt acutely across the geologic world, mitigated only by the model he left us of how the combination of intellectual rigor, originality and passion can lead to new insights into how planets work.” 

When he was born in 1959 in Harbin, China, he was called Yin Jishing — the name Jishing, meaning “helped by others,” was chosen because a neighbor had given his mother prenatal supplements to support the family’s meager rations. The state demanded that his name be changed, and he became Yin An. (He reversed the names later, in line with the Western convention for using surnames after given names.) 

Yin often said growing up during the Cultural Revolution provided him with both a social model to react against and the motivation to pursue a career in science. Eventually, he earned a doctorate from the University of Southern California in 1988; he had joined UCLA a year earlier, pending his doctoral defense. 

Among his many important accomplishments was his documenting, in the early 2000s, a seismic gap in China that would be capable of generating an earthquake of a similar magnitude to the 1976 temblor in nearby Tangshan that killed more than a quarter million people. He also developed a model for relating slow earthquakes to the propagation of tectonic tremors.

More recently, Yin applied his expertise to study tectonic processes on other bodies in our solar system. His investigations led to the proposal that Mars had once experienced localized plate tectonics and helped explain the origin of the famous tiger-stripe fractures on Saturn’s moon Enceladus. He published more than 200 papers and his work was cited more than 38,000 times by other scientists. 

Equal to Yin’s remarkable research contributions were those as a supervisor, teacher and mentor. Of his nearly 40 graduate students, 11 have gone on to become university professors, and one, Jessica Watkins, is a NASA astronaut who was selected for the Artemis lunar lander team. Yin was especially admired by a new generation of Chinese scientists, many of whom consider him one of the most important geologists their nation has ever produced. 

“When I was a student, Yin was the greatest geologist I looked up to,” said Peng Ni, an assistant professor of Earth, planetary and space sciences who grew up in China and joined the UCLA faculty in 2023. “As a professor in the department myself, I came to realize how approachable, sincere and enthusiastic he was. He loved collaborating with young scientists, and I will miss him deeply.” 

Indeed, Yin was a magnet for young scientists from around the world. More than 40 international visiting scholars came to UCLA to learn from him. Harrison said by the time those scholars left UCLA, they had become apostles of Yin’s worldview: No excuses, hard work, astringent logic and a healthy skepticism of intellectual authority.

Yin was also passionate about his teaching of undergraduates, and he was the backbone of the UCLA geology field research curriculum for more than 30 years. 

“Professor Yin inspired me to become a structural geologist and loved few things more than leading young undergraduates into the field,” said Terry Lee, who earned a bachelor’s degree from UCLA in 2022 and is now pursuing a doctorate at the University of Nevada, Reno. “He was a great mentor and educator to the undergraduate community. He instilled in me a strong work ethic and nurtured a creative mindset which serves me in my graduate work today.”