Watch:Jan.12 Dr. Xian SHI: Multifaceted Cometary Activity Revealed by Rosetta

Speaker: Dr. Xian SHI
Shanghai Astronomical Observatory
Jan. 12, 2023
4:00 pm GMT +8
Watch it on Bilibili 

The activity of comets produces some of the most spectacular astronomical phenomena ever recorded by human beings. However, to understand the nature of the activity with ground-based observations has proved difficult since a comet’s nucleus is small and usually shrouded by a dusty coma that is tens of thousands of times larger in size. In 1986, the first spacecraft flybys of a comet were carried out during the return of Halley’s comet, revealing unexpected fine structures of gas and dust comae in the near-nucleus space.  But it was not until nearly 30 years later when the Rosetta mission of ESA presented us the opportunity to closely monitor a comet’s activity through its perihelion passage. During Rosetta’s rendezvous with comet 67P/Churyumov-Gerasimenko from 2014 to 2016, the on-board scientific camera system OSIRIS captured a diversity of dust activity at unprecedented spatial and temporal resolutions. Besides diurnally repetitive, regular activity of gas and dust emissions, OSIRIS observations also show spontaneous outbursts, ejections of large trunks, and activity-induced surface changes on the nucleus. In this talk, I will introduce observations of various forms of dust activity on 67P, and our investigation to explain possible underlying mechanisms. Our analysis indicates that driving forces behind different forms of cometary activity could be extremely diverse and more complex than previously expected. Furthermore, the activity results in significant resurfacing of the nucleus and redistribution of volatiles. Understanding these physical processes could reveal essential knowledge of a comet’s formation and evolution.

About the Speaker

Xian Shi received her PhD degree in 2012 from Shanghai Astronomical Observatory, Chinese Academy of Sciences. Afterwards, she held a two-year postdoc position at the Institute of Planetary Research, German Aerospace Center, investigating the dynamical history of the Martian moon Phobos. In 2014, she joined Max Planck Institute for Solar System Research and became a team member of ESA’s Rosetta mission. Her primary research topic is cometary activity using high-resolution imaging data from Rosetta’s scientific camera system OSIRIS. She was also heavily involved in the planning, operation, and calibration of OSIRIS observations. She moved to Shanghai Astronomical Observatory in spring 2021 and established a research group on the exploration and investigation of small bodies in the Solar System. Her main research interest is to understand the formation and evolution of Solar System’s small bodies as well as their relationship to the origin and modification of planetary habitability.


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