The first interplanetary mission of China reached its second anniversary in orbit around Mars on February 10th, but it remains silent on the fate of the Zhurong rover. The rover of the Tianwen-1 mission entered hibernation in May 2022 due to the decrease in solar energy available to the spacecraft during the northern hemisphere winter on the red planet.
Zhurong was expected to wake up in December during the Martian spring equinox period. But China and its space authorities have remained silent on the status of the rover.
The strange silence
Chinese state media celebrated the second anniversary with short articles highlighting the results of the Mars orbiter Tianwen-1 and briefly mentioning the Zhurong rover. This is a strange attitude compared to the typical triumphalistic tones that highlight Chinese space power. Furthermore, no new images have been released of either the orbiter or the rover.
Zhurong was expected to wake up autonomously when two distinct conditions were met. The awakening from hibernation was supposed to occur upon the rover reaching a temperature of at least 15°C and generating more than 140 watts of power. Both conditions were supposed to be reached in December.
The rover does not carry a radioisotope heating unit, like other rovers including the Chinese lunar explorers Yutu. But it instead has a chemical substance called n-undecane that can store thermal energy. The substance absorbs heat by melting during the day, while it solidifies and releases heat during the night.
Dust storms in Utopia Planitia could have affected the rover’s ability to generate heat and light. This could potentially be the problem that explains Zhurong’s silence and could leave hope that the rover will reactivate under warmer conditions or when Martian winds clear its solar panels.
The Tianwen-1 mission, despite the apparent problem with Zhurong’s operations, was a huge success. China’s first independent interplanetary expedition made the country the second, after the United States, to successfully use a rover on Mars.
Both the Tianwen-1 orbiter and Zhurong completed their missions and won international awards and recognition, and updates, both positive and negative, on the fate of their missions have always come on time from China. Previously, the Yutu lunar rover experienced a malfunction in early 2014. However, the country remains silent on the fate of Zhurong. Despite this deafening silence, China is planning a Mars sample return mission called Tianwen 3, to be launched no earlier than 2028.