China became the second country to successfully operate a rover on Mars when its Zhurong rover touched down in Utopia Planitia on May 15, 2021, as part of the Tianwen-1 mission. What made the achievement unusual was its ambition: in a single launch, China deployed an orbiter, a lander, and a rover, accomplishing in one mission what other space agencies had spread across several. Since landing, the mission has returned a stream of scientific results, from radar images of Mars’s subsurface to evidence that liquid water was active on the planet far more recently than expected.
How Tianwen-1 Reached the Surface
Tianwen-1 launched in July 2020 during the same transfer window that sent NASA’s Perseverance rover and the UAE’s Hope orbiter toward Mars. After a roughly seven-month cruise, the spacecraft entered Mars orbit in February 2021 and spent about three months surveying candidate landing sites from above before committing to a landing. The entry vehicle touched down in the southern part of Utopia Planitia at 7:18 a.m. Beijing time on May 15, 2021, using a combination of aerodynamic braking, parachute deployment, and retrorocket firing to slow from interplanetary speed to a gentle stop on the surface.1Astrodynamics. Tianwen-1 Mars entry vehicle trajectory and atmosphere reconstruction preliminary analysis
The landing region was chosen after extensive analysis of both engineering safety and scientific interest. The candidate zone, stretching from roughly 109° to 133° East longitude and 23° to 30° North latitude, sits at a low elevation of about −4,230 meters, which is helpful because more atmosphere above the landing site gives the parachute more time to work. Analysis showed that 98 percent of the region has slopes gentler than 8 degrees, and a hazard map was generated combining surface slope data, crater density, and rock abundance to identify the safest spots within it.2Earth and Space Science. Characterization of the Candidate Landing Region for Tianwen‐1—China’s First Mission to Mars
The Zhurong Rover and Its Instruments
Zhurong weighs about 240 kilograms and was designed for at least 90 Martian days (sols) of surface operations, though it operated well beyond that target before entering hibernation. The rover carries six scientific instruments: a pair of navigation and terrain cameras, a multispectral camera for mineralogy, a ground-penetrating radar to probe beneath the surface, a laser-based composition detector, a magnetometer, and a weather station.3The Innovation. Zhurong: Features and mission of China’s first Mars rover
One engineering detail that sets Zhurong apart from some earlier rovers is its active suspension system. Mars’s surface is rockier than the Moon’s, and Zhurong’s suspension uses a main-and-auxiliary rocker arm design with clutches at the connection points. This allows the rover to lift, lower, and even retract individual wheels when stuck, giving it a stronger ability to climb over obstacles or free itself from soft terrain.4The Innovation. Zhurong: Features and mission of China’s first Mars rover That capability matters in a place where a stuck wheel can end a mission, as the Spirit rover demonstrated years earlier.
What the Radar Found Underground
Perhaps Zhurong’s most striking scientific contribution so far comes from its ground-penetrating radar, which sends pulses into the soil and reads the echoes bouncing off buried layers. Over a traverse of roughly 1,171 meters, the radar built a detailed profile of the ground beneath the rover, revealing a multi-layered structure extending about 70 meters deep below a thin surface layer of regolith less than 10 meters thick.5PubMed Central. Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar
Researchers divided what they saw into four distinct layers. The top layer, less than 10 meters thick, appears to be typical Martian soil. Below that, from roughly 10 to 30 meters deep, scattered rocky blocks sit within a finer matrix, with the rocks getting larger as you go deeper. A third layer, from 30 to 80 meters, contains even larger blocks packed more densely together. The changes between layers are gradual rather than sharp, with no obvious hard boundary separating them.6Nature. Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar
The researchers interpreted this layered structure as the product of repeated large-scale flooding events. The idea is that episodic hydraulic floods, likely during Mars’s Late Hesperian to Amazonian periods, deposited sediment and debris in waves that gradually filled in Utopia Planitia. While alternative explanations haven’t been ruled out, the radar profile is among the most direct subsurface evidence anyone has gathered on Mars for these kinds of flood deposits.7PubMed Central. Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar
Surprisingly Recent Water Activity
Zhurong’s spectral instruments added another dimension to the water story. Using short-wave infrared data, the rover identified hydrated sulfate and silica minerals on the surface near its landing site. These minerals were associated with bright-toned rocks that appear to be duricrust, a hardened layer formed when mineral-rich water cements loose soil. The key implication is that this duricrust likely formed through either groundwater rising to the surface or subsurface ice melting, processes that require substantial amounts of liquid water.8PubMed Central. Zhurong reveals recent aqueous activities in Utopia Planitia, Mars
What makes this finding particularly interesting is the age of the terrain. Utopia Planitia’s surface here dates to the Amazonian epoch, the most recent period of Martian geological history. Most previous evidence for water on Mars had been confined to much older terrain. Finding signs of liquid water activity on Amazonian-age surfaces suggests that Mars’s water cycle remained more active, more recently, than scientists had generally assumed.9PubMed Central. Zhurong reveals recent aqueous activities in Utopia Planitia, Mars For anyone thinking about whether Mars might still harbor pockets of liquid water today, even deep underground, that’s an encouraging data point.
Surface Rock and Soil Chemistry
Zhurong carries a laser instrument called MarSCoDe that can zap rocks from a distance and analyze the light emitted by the resulting tiny plasma flash. This technique, laser-induced breakdown spectroscopy, lets researchers figure out what elements are present in rocks and soil without the rover having to drive right up to them. Analysis of trace elements like lithium, strontium, and rubidium indicates that the rocks at the landing site are primarily igneous in origin, likely from the most recent lava flows that covered the area during the Amazonian epoch. The main secondary minerals detected are small amounts of sulfates, which appear to have formed from acidic weathering caused by relatively recent surface brine. Clay minerals, which are a common sign of extensive water-rock interaction, seem either absent or very sparse.10Journal of Geophysical Research: Planets. Alkali Trace Elements Observed by MarSCoDe LIBS at Zhurong Landing Site on Mars: Quantitative Analysis and Its Geological Implications
Separate cluster analysis of the MarSCoDe data suggests there may be small amounts of altered minerals like montmorillonite near the landing site, though the degree of alteration appears minor. Researchers attribute this to weak aqueous alteration, possibly from interactions with atmospheric moisture or groundwater.11PubMed. Classification of martian rocks and soils at Tianwen-1 landing site based on laser-induced breakdown spectroscopy data of MarSCoDe Taken together, the geochemistry paints a picture of a volcanic landscape that was lightly touched by water but never saw the kind of prolonged, lake-filling aqueous environment found at some other Martian locations.
A Weather Station on Mars
While the rover was the headline act, the Tianwen-1 lander also served as a fixed meteorological station. Its Mars Climate Station instrument recorded air temperature, atmospheric pressure, wind speed, and wind direction over the first 325 sols of the mission, building one of the most detailed weather datasets collected at this latitude on Mars.12Scientific Reports. Initial results of the meteorological data from the first 325 sols of the Tianwen-1 mission
Mars weather data from Zhurong’s location matters because Utopia Planitia is a flat, low-lying basin in the northern hemisphere, a different environment from the equatorial crater where NASA’s Curiosity operates or the ancient river delta where Perseverance is working. Having weather data from multiple sites helps scientists understand global atmospheric circulation patterns, not just local conditions. One practical finding from combining the weather data with imagery was that wind speed appears to be a critical factor controlling how quickly dust settles on surfaces.13Geophysical Research Letters. Dust Deposition at Zhurong Landing Site From Multispectral Camera Observations That matters directly for solar-powered missions like Zhurong, since dust accumulation on solar panels is a constant threat to power generation. In fact, dust buildup is widely believed to be a factor in Zhurong’s loss of contact after it entered hibernation for the Martian winter and failed to wake up as expected.
Mapping the Entire Planet from Orbit
While Zhurong worked on the ground, the Tianwen-1 orbiter circled above collecting data of its own. Its Moderate Resolution Imaging Camera, MoRIC, was designed to photograph the Martian surface globally with enough overlap between adjacent images to build three-dimensional topographic models. Testing confirmed that MoRIC’s elevation accuracy is about one ground sampling distance, meaning the height measurements are roughly as precise as the horizontal resolution of the images.14Journal of Remote Sensing. Topographic Mapping Capability Analysis of Moderate Resolution Imaging Camera (MoRIC) Imagery of Tianwen-1 Mars Mission
The orbiter also carried a mineralogical spectrometer that gathered visible and near-infrared spectral data. Combining 10,572 processed MoRIC images with the spectrometer’s 325 strips of spectral data, researchers produced a new global color-image map of Mars at 76-meter resolution with horizontal positioning accuracy of about 68 meters. The team describes this as the highest-resolution global true-color image map of Mars currently available, filling a gap in high-precision positioning for Mars imagery at the tens-of-meters scale.15Science Bulletin. A 76-m per pixel global color image dataset and map of Mars by Tianwen-1 That kind of product is valuable not just for Chinese missions but for any future Mars exploration that needs a detailed, accurately positioned map of the whole planet.
Observing How Mars Loses Its Atmosphere
The Tianwen-1 orbiter also contributed to an area of Mars science that doesn’t get as much public attention as surface geology: understanding how the planet’s atmosphere escapes into space. Mars lacks a global magnetic field, which means the solar wind can interact directly with the upper atmosphere and strip away charged particles. The orbiter detected oxygen ion “plumes,” streams of energized oxygen ions being accelerated away from Mars by the electric field carried by the solar wind.
Joint observations between Tianwen-1 and NASA’s MAVEN orbiter, which has been studying Mars’s upper atmosphere since 2014, confirmed that convection electric fields are the energization mechanism driving these plumes, accelerating ions to energies above 15 keV. Most of the plumes appear to originate from middle and low latitudes on the dayside of Mars’s northern hemisphere.16Icarus. Tianwen-1 and MAVEN observations of Martian oxygen ion plumes Having two spacecraft measuring the same phenomenon simultaneously allows researchers to disentangle spatial patterns from temporal changes, something a single orbiter can’t easily do. These atmospheric escape measurements feed into the broader question of where Mars’s once-thicker atmosphere went and how quickly the planet dried out.
The Deep Space Network That Made It Possible
Communicating with a spacecraft hundreds of millions of kilometers away requires dedicated ground infrastructure. For Tianwen-1, China relied on its Chinese Deep Space Network, with stations in Jiamusi and Kashgar within China and a third station in Zapala, Argentina, providing coverage from the southern hemisphere. Orbit determination during the interplanetary cruise also drew on China’s very long baseline interferometry network, a system of radio telescopes in Beijing, Kunming, Urumqi, and Shanghai, plus a data processing center in Shanghai’s Sheshan district.17Advances in Space Research. Orbit determination of China’s first mars probe Tianwen-1 during interplanetary cruise
The interferometry technique works by measuring tiny differences in when a radio signal from the spacecraft arrives at widely separated antennas, then using those differences to calculate the spacecraft’s position with high precision. Building this network was as much a prerequisite for Mars exploration as building the rocket or the rover itself. Without it, you can’t navigate accurately enough to hit a target the size of a landing ellipse after a seven-month flight. The Argentine station was a strategic addition, since Mars sometimes sits in the sky where it’s only visible from the southern hemisphere, and relying solely on Chinese territory would have left gaps in tracking coverage.
Plans for Mars Sample Return
China has publicly discussed plans for a Mars sample return mission, tentatively targeted for the late 2020s or early 2030s. Such a mission would involve landing on Mars, collecting soil and rock samples, launching them off the surface in a small ascent vehicle, rendezvousing with an orbiting spacecraft, and then flying the samples back to Earth. Each of those steps is an enormous engineering challenge on its own, and stringing them together into a single campaign is arguably the most complex robotic mission ever attempted.
One area where Chinese engineers have been publishing preparatory research is the orbital rendezvous phase, where a sample container launched from the Martian surface has to meet up with a waiting orbiter. Navigation errors at Mars are much larger than near Earth because communication delays make real-time ground control impractical. A proposed multi-impulse planning method addresses this by updating the maneuver sequence in real time as fresh navigation data comes in before each thruster firing. In simulations, this approach reduced the terminal miss distance to within 1 kilometer, an improvement of about 80 percent compared with a pre-planned approach that doesn’t adapt to updated information.18Journal of Physics: Conference Series. Real-time planning of rendezvous phasing on mars orbit with large navigation errors That kind of precision is necessary for a rendezvous where both objects are small, moving fast, and far from any ground controller who could intervene quickly.
The data-sharing dimension of future missions has also been a topic of discussion within the Chinese Mars science community. At a workshop in Chengdu, participants emphasized the need for reliable, standardized data distribution to scientists in a timely manner, reflecting expectations from both the scientific and engineering sides of the program.19PubMed Central. Tianwen-1 and China’s Mars exploration program How open the data ultimately becomes will affect whether Tianwen-1’s results get folded into the broader international picture of Mars or remain somewhat siloed.
What Happened to Zhurong
Zhurong’s last communication with Earth came in May 2022, roughly a year after landing, as the rover entered hibernation mode for the Martian winter. Solar-powered and located in Mars’s northern mid-latitudes, the rover was expected to lose enough sunlight and warmth during winter that shutting down and waiting for spring was the only option. The plan was for Zhurong to wake up automatically once conditions improved, around December 2022. It never did.
Chinese space officials have acknowledged that the rover has not responded to wake-up attempts. While no official cause of death has been declared, dust accumulation on the solar panels is a leading suspect. As the weather data from Zhurong’s own instruments showed, wind speed plays a significant role in dust deposition rates at the site. Without a dust-clearing event, like the wind gusts that periodically cleaned NASA’s Opportunity rover’s panels, a thick enough dust layer would prevent the solar panels from generating the power needed to warm the electronics above their survival threshold.
Even if Zhurong never wakes up, its scientific output exceeded original expectations. The rover operated for over 350 sols and traveled nearly two kilometers, collecting the subsurface radar data, mineral detections, and geochemistry measurements described above. The Tianwen-1 orbiter, meanwhile, continues to function, still gathering imaging and spectral data from its perch above the planet.