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Ice-Rich Ceres is Focus of New Book by PSI’s Jian-Yang Li

April 15, 2022

ceres book cover

Credit: World Scientific/Amanda Yun

Thanks to NASA's Dawn mission, the last half-decade has witnessed a significant advance in our understanding of Ceres. A new book by Planetary Science Institute Senior Scientist Jian-Yang Li sheds light on the dwarf planet Ceres, the most water-rich body in the inner Solar System after Earth that shows evidence of brine driven activity in its recent history, or even possibly at the present. 

In “Ceres: An Ice-Rich World in the Inner Solar System,” Li and co-author Julie C. Castillo-Rogez of NASA’s Jet Propulsion Laboratory provide a thorough review of the discoveries by the Dawn mission through its three-and-a-half years of exploration, and summarizes the current state of knowledge of this dwarf planet. 

“Before the Dawn mission, the nature of Ceres had remained mysterious, although the dwarf planet’s large water content had been known since the 1970s.  The recent investigation of Ceres by Dawn revealed tremendous similarities between Ceres and the outer Solar System icy moons and dwarf planets, such as an ice-rich crust, expressions of cryovolcanic activity, and the occurrence of organics and salts,” Li said. “More intriguingly, Dawn discovered evidence for recent activity driven by salt-rich liquids sourced from the deep interior. The presence of liquid and organic matter in Ceres bears important implications for astrobiology and even more so as Ceres may be representative of the population of outer Solar System bodies that brought in volatiles and organics to the terrestrial planets.” 

Li formally joined the Dawn mission team as a post-doctoral researcher in 2007, and then as a Vesta Participating Scientist, Ceres Guest Investigator, and finally as a science team co-investigator. He started to study Ceres using the Hubble Space Telescope data as part of his Ph.D. thesis, and then became fully involved in Dawn’s operations and researches of Ceres. 

“Ceres holds profound scientific values in a range of planetary science research areas. My colleagues and I are working towards potential future explorations of Ceres. A comprehensive review of the current state of knowledge of Ceres would be desirable and timely. With the encouragement of Prof. Wing-Huen Ip, who is the Editor of the Advances in Planetary Science book series, we decided to write this book,” Li said. 

“The book starts with a historical overview of the exploration of Ceres before Dawn, from its discovery in the 19th century to extensive characterization with telescopes over the past 50 years. After an overview of the Dawn mission, this book synthesizes various aspects of Dawn’s discoveries, including surface composition, geology, expressions of water ice, interior structure, and recent activity. The astrobiological significance of Ceres inferred from this new knowledge is then addressed. The book concludes with a summary of open questions and motivations for follow-on research and exploration” Li said. 

NASA’s Dawn mission to giant asteroid Vesta and Ceres, the two largest bodies in the main asteroid belt, launched in 2007 on a journey that covered 4.3 billion miles (6.9 billion kilometers). In 2011, when Dawn arrived at Vesta, the second-largest world in the main asteroid belt, the spacecraft became the first to orbit a body in the region between Mars and Jupiter. In 2015, when Dawn went into orbit around Ceres, a dwarf planet that is also the largest world in the asteroid belt, the mission became the first to visit a dwarf planet and go into orbit around two destinations beyond Earth. 

Dawn ended its extended mission when a key fuel ran low. Hydrazine was used to control the spacecraft’s orientation in space. And Dawn only had as much as it carried from Earth. When Dawn ran out of hydrazine, it was no longer able to point its antennas toward Earth for communication. Once communication was lost, mission managers attempted communicating for a limited period – a couple of days – to verify that there was not an unexpected problem. When there was no response, they officially ended Dawn’s mission on Nov. 1, 2018. 

Ceres remains a rich research target for scientists. “A few studies have been completed or are under way to evaluate different approaches to explore the liquid in the interior of Ceres, the distribution, current state, the composition, and the biological implications. These include orbiter, lander, and sample return. Several scientifically valuable sites on Ceres have been identified as the targets of future explorations,” Li said. “In the meantime, we will continue to study Ceres from the Earth through all possible ways, such as remote observations, laboratory experiments, terrestrial analogs, and theoretical modeling, together with the relevant technology development to prepare for the return to Ceres.”

jian-yang li 

Jian-Yang Li


Alan Fischer

Public Information Officer


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Jian-Yang Li

Senior Scientist

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