Interstellar Object 3I/ATLAS Observed from Mars by China’s Tianwen-1 Spacecraft
11 affiliations
- 1Chinese Academy of Sciences
- 2University of Chinese Academy of Sciences
- 3Sun Yat-sen University
- 4Universidad Diego Portales
- 5Macau University of Science and Technology
- 6Shenzhen Campus of Sun Yat-sen University
- 7Lanzhou Institute of Physics
- 8Beijing Aerospace Command and Control Center
- 9Beijing Institute of Spacecraft System Engineering
- 10Shanghai Institute of Satellite Engineering
- 11Lunar Exploration and Space Engineering Center
Abstract
China’s Tianwen-1 Mars orbiter successfully imaged the third interstellar object, 3I/ATLAS, during its close encounter with Mars using the onboard HiRIC CMOS camera. This is China’s first deep-space observation of an astronomical object. These observations constitute the first imaging of this object from a vantage point significantly out of its orbital plane, providing a unique constraint on dust dynamics. Three observing epochs between 2025 September 30 and October 3 reveal clear changes in coma and tail morphology driven by the rapidly evolving viewing geometry. Comparison with Finson–Probstein dust dynamical models indicates that the coma is dominated by large grains with solar radiation pressure parameter β ≈ 10 −3 –10 −2 , corresponding to grain sizes of a few hundreds of microns. The extent of the sunward coma implies dust ejection velocities of 3–10 m s −1 . Despite the morphological evolution, the azimuthally averaged surface brightness profile remains nearly unchanged through the three epochs, transitioning from a radial slope near −1 close to the nucleus to slightly steeper than −1.5 at larger cometocentric distances, consistent with steady-state dust outflow accelerated by solar radiation pressure. Photometry yields an average Afρ ∼ (2.0 ± 0.2) × 10 4 cm and a corresponding dust mass loss rate of M ̇ ∼ 1 0 3 kg s − 1 .
Related
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- Coma Physics of an Interstellar Object: JWST Spatial–Spectral Mapping of 3I/ATLAS
- Characterization of the anisotropic dust activity of interstellar comet 3I/ATLAS
- High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS
BibTeX
@article{任2026interstellar,
title = {{Interstellar Object 3I/ATLAS Observed from Mars by China’s Tianwen-1 Spacecraft}},
author = {Xin 鑫 Ren 任 and Wei 韦 Yan 严 and Ruining Zhao and Shu Wang and Xingye Gao and Qiang 强 Fu 付 and Qing Zhang and Bin Yang and Man-To Hui and Zhiyong Xiao and Xiaodong Liu and Cunhui Li and Renhao Tian and Wenguang 文光 Liu 刘 and Dong 栋 Wang 王 and Shaoran Liu and Cong Ren and Jie Dong and Xinbo Zhu and Pan Xie and Jian‐Yang Li and Yan 言 Geng 耿 and J S Liu},
journal = {The Astrophysical Journal Letters},
year = {2026},
month = may,
doi = {10.3847/2041-8213/ae61b3},
url = {https://doi.org/10.3847/2041-8213/ae61b3},
note = {CC BY},
}
RIS
TY - JOUR
TI - Interstellar Object 3I/ATLAS Observed from Mars by China’s Tianwen-1 Spacecraft
AU - Xin 鑫 Ren 任
AU - Wei 韦 Yan 严
AU - Ruining Zhao
AU - Shu Wang
AU - Xingye Gao
AU - Qiang 强 Fu 付
AU - Qing Zhang
AU - Bin Yang
AU - Man-To Hui
AU - Zhiyong Xiao
AU - Xiaodong Liu
AU - Cunhui Li
AU - Renhao Tian
AU - Wenguang 文光 Liu 刘
AU - Dong 栋 Wang 王
AU - Shaoran Liu
AU - Cong Ren
AU - Jie Dong
AU - Xinbo Zhu
AU - Pan Xie
AU - Jian‐Yang Li
AU - Yan 言 Geng 耿
AU - J S Liu
PY - 2026
DA - 2026/05/14
JO - The Astrophysical Journal Letters
DO - 10.3847/2041-8213/ae61b3
UR - https://doi.org/10.3847/2041-8213/ae61b3
AB - China’s Tianwen-1 Mars orbiter successfully imaged the third interstellar object, 3I/ATLAS, during its close encounter with Mars using the onboard HiRIC CMOS camera. This is China’s first deep-space observation of an astronomical object. These observations constitute the first imaging of this object from a vantage point significantly out of its orbital plane, providing a unique constraint on dust dynamics. Three observing epochs between 2025 September 30 and October 3 reveal clear changes in coma and tail morphology driven by the rapidly evolving viewing geometry. Comparison with Finson–Probstein dust dynamical models indicates that the coma is dominated by large grains with solar radiation pressure parameter β ≈ 10 −3 –10 −2 , corresponding to grain sizes of a few hundreds of microns. The extent of the sunward coma implies dust ejection velocities of 3–10 m s −1 . Despite the morphological evolution, the azimuthally averaged surface brightness profile remains nearly unchanged through the three epochs, transitioning from a radial slope near −1 close to the nucleus to slightly steeper than −1.5 at larger cometocentric distances, consistent with steady-state dust outflow accelerated by solar radiation pressure. Photometry yields an average Afρ ∼ (2.0 ± 0.2) × 10 4 cm and a corresponding dust mass loss rate of M ̇ ∼ 1 0 3 kg s − 1 .
SN - 2041-8205
SN - 2041-8213
ER -