Research |

Origin of Saturn's rings

Sun, 01 Mar 2026 00:00:00 +0000

The origin of Saturn’s rings has been debated for decades. Measurements from Voyager and Cassini have suggested that the rings could be as young as ~100 Myr and composed of nearly pure water ice. Several scenarios have been proposed to explain these properties. One hypothesis is that the rings formed through the recent tidal disruption of a pre-existing moon, Chrysalis, which experienced a close encounter with Saturn following its highly eccentric orbit. However, the mechanism by which this hypothesis would have formed the rings remains largely unexplored, in particular, whether Chrysalis could supply ring material of the desired mass and composition. To address these questions, we perform smoothed particle hydrodynamics simulations to investigate the tidal response of Chrysalis during close encounters with Saturn. Our results demonstrate that preferential tidal stripping of the ice mantle from a differentiated Chrysalis can produce rings with both mass and composition resembling the present rings, provided that the closest encounter occurs between the parabolic Roche limits for ice ~1.53 $R_S$ and rock ~1.07 $R_S$. Moreover, multiple close encounters can extend the effective disruption limit by spinning up the body, enhancing the tidal stripping efficiency. Following close encounters, the rocky remnant of Chrysalis would have been removed in less than few kyr, either by collision with Saturn or ejection onto a hyperbolic orbit. These findings support the hypothesis that Saturn’s rings could originate from a recent lost moon, and imply a highly dynamical evolution of the Saturnian system over the past few hundred million years.

Y. Jiao, F. Nimmo, J. Wisdom, et al. Investigating tidal stripping of a pre-existing moon as the origin of Saturn’s young icy rings. The Astrophysical Journal Letters (accepted)

Smoothed particle hydrodynamics

Sun, 01 Mar 2026 00:00:00 +0000

Smoothed particle hydrodynamics (SPH) is a mesh-free Lagrangian particle method that represents physical quantities using a smoothing kernel and solves the hydrodynamic conservation equations for mass, momentum, and energy. The SPH method has been widely used to model hypervelocity impacts and tidal responses of planetary bodies. Our SPH code is publicly available at .

Y. Jiao, X. Yan, B. Cheng, et al. SPH-DEM modeling of hypervelocity impacts on rubble-pile asteroids. Monthly Notices of the Royal Astronomical Society (2023)

Collisional evolution of asteroids

Sun, 01 Jun 2025 00:00:00 +0000

Important

This page is under development.

Y. Jiao, B. Cheng, W. Dai, et al. Giant craters on 253 Mathilde revealing the cohesive porous interior of carbonaceous parent bodies. Nature Geoscience (under review)

T. Baoyin, Y. Jiao, B. Cheng. Predicting the collision history of basaltic asteroids from parametrized shapes with an artificial neural network. Monthly Notices of the Royal Astronomical Society (2025)

Lunar originated asteroids

Sun, 01 Jun 2025 00:00:00 +0000

Important

This page is under development.

Y. Jiao, B. Cheng, H. Baoyin. Probing the Moon from future asteroid impacts: a review. Science China Technological Sciences (2026)

Y. He, Y. Wu, Y. Jiao, et al. Observation timelines for the potential lunar impact of asteroid 2024YR4. The Astrophysical Journal (2026)

Y. Wu, Y. Jiao, W. Dai, et al. Detectability of lunar-origin asteroids in the LSST era. The Astrophysical Journal (2026)

Y. Jiao, B. Cheng, Y. Huang, et al. Asteroid Kamo`oalewa’s journey from the lunar Giordano Bruno crater to Earth 1:1 resonance. Nature Astronomy (2024)

Fly to Apophis in 2029

Wed, 01 Jan 2025 00:00:00 +0000

The Student-led Threatening Asteroid Reconnaissance of Tsinghua (START) is a low-cost, rapid-response minisatellite mission designed to investigate the near-Earth asteroid (99942) Apophis. During its Earth close approach in April 2029, Apophis will experience significant terrestrial tidal forces, providing an unprecedented opportunity to observe the real-time physical and dynamical evolution of a rubble-pile asteroid. The 200-kg spacecraft is scheduled to be launched as a secondary payload into low Earth orbit in early 2028, and then utilize solar electric propulsion to autonomously transfer to a 38,000-km geocentric orbit. START will execute a high-speed flyby of Apophis wtih a closest approach of 7 km at its perigee. The payload suite consists of a high-resolution narrow-field camera, a wide-field navigation camera, and dual visible-to-near-infrared hyperspectral imagers. By acquiring centimeter-scale imagery and reflectance spectra, the mission will characterize the asteroid’s surface morphology and composition, monitor immediate tidally induced surface modifications, and constrain its internal structure. Ultimately, START will provide geometrically complementary, high-cadence datasets to international flagship missions during the highly dynamic perigee passage, demonstrating a highly scalable and cost-effective architecture for future planetary defense and small-body exploration.

Y. Wu, Y. Li, B. Zheng, …, Y. Jiao, et al. The START mission: probing the 2029 Apophis flyby via a low-cost geocentric smallsat. The Planetary Science Journal (under review)

Kinetic impact for asteroid deflection

Sun, 01 Jan 2023 00:00:00 +0000

Important

This page is under development.

Y. Jiao, X. Yan, B. Cheng, et al. SPH-DEM modeling of hypervelocity impacts on rubble-pile asteroids. Monthly Notices of the Royal Astronomical Society (2023)

Y. Jiao, B. Cheng, H. Baoyin. Optimal kinetic-impact geometry for asteroid deflection exploiting Delta-V hodograph. Journal of Guidance, Control, and Dynamics (2022)