A Mars probe just acted as a giant 'X-ray machine' to see inside the Sun's atmosphere.
April 17, 2026
Original Paper
Probing Coronal Activity Using Radio Signals Based on the 2021 superior conjunction of Mars: the Downlink Data from Tianwen-1
arXiv · 2604.13670
The Takeaway
While the Tianwen-1 probe was orbiting Mars, its radio signal home had to pass right through the Sun's outer atmosphere. Scientists used that signal to detect high-speed solar winds and massive solar 'burps' that were otherwise invisible. It turns a standard communication link into a high-precision scientific instrument. We can now study the Sun's most violent activity without needing to send a dedicated probe into the heat. This helps us better predict solar storms that can knock out power grids on Earth.
From the abstract
During the first superior conjunction of the Tianwen-1 Mars probe in October 2021, its downlink signal received by the Wuqing 70-m radio telescope passed within 4.53 solar radii of the Sun. The signal was significantly perturbed by the solar wind, providing a mechanism to probe coronal activity. We analyze the Doppler frequency scintillation spectrum of the solar wind within 10 solar radii to derive a characteristic frequency scintillation parameter. Statistical analysis indicates this parameter