China's plans to explore the Solar System: The Tianwen Missions
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| Tianwen-1 imaged by a deployable camera. Credit: CNSA/PEC/Ling Xin CC BY 4.0 |
Over the last few decades, China has been rapidly advancing there space program. The Peoples Republic of China launched their first astronaut into space in 2003, and now they have rovers on the Moon and Mars, with many more ambitous missions on their way. Below are current, planned, and proposed Tianwen missions. We'll start with the first one, Tianwen-1, which launched back in 2020.
Tianwen-1/Zhurong
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| Zhurong and the Tianwen-1 lander imaged by a deployable camera. Credit: CNSA/China News Service CC BY 3.0 |
You can build your own Tianwen-1 orbiter out of LEGO here.
Tianwen-1 was China's first mission to land on Mars, but it wasn't their first attempt. China had a rideshare payload aboard Russia's Fobos-Grunt mission, but both burned up in Earth's atmosphere, and never made it to the red planet.
The mission consisted of three parts: an orbiter, a lander, and a rover. The rover was named "Zhurong," after a Chinese thythological character associated with fire and light. The mission launched aboard the large Long March 5 rocket in 2020, and entered orbit around Mars on February 10, 2021.
The Tianwen-1 orbiter did not release the capsule containing the lander and rover on its approach, instead holding on to it until it located a suitible landing location. After a location was selected, at Utopia Planitia, the spacecraft temporarily deorbited itself and released the capsule. After the capsule was released, the orbiter raised its orbit again, so it wouldn't crash into the planet.
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| Tianwen-1 lander displaying China's flag, imaged by the Zhurong rover. Credit: CNSA/Huang, X., Xu, C., Hu, J. et al. CC BY 4.0 |
The landing occured on May 14, 2021, and the lander successfully touched down on the Martian surface. On May 22, the Zhurong rover drove off the lander to explore the Martion surface. This made Chine only the second country to put a rover on Mars.
Zhurong deployed a camera on the surface, which was able to take an image with both the rover and lander in frame. The rover drove to the lander's backshell and parachute, which it imaged on July 12, 2021.
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| Tianwen-1 lander's backshell and parachute imaged by Zhurong. Credit: CNSA/PEC |
As of October 2023, little news as been heard about Zhurong for some months. The rover entered hibernation mode on May 20, 2022, for the Martian winter. It was planned to wake up in December, but images from NASA orbiters have shown that the rover hasn't budged. While China hasn't admitted to a failure of the rover, it is likely dead. While Zhurong is probably lost, it did outlast its primary mission, which was finished on August 18, 2021. Meanwhile, the Tianwen-1 orbiter is still active.
The Target
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| Image of Mars from the Mars Global Surveyor Orbiter. Credit: NASA/JPL/MSSS |
- Date Discovered: Known To The Ancients
- Radius: 3389.5 Kilometres
- Surface Pressure: 0.0099 Atmospheres
- Mass: 6.4169x10^23 Kilograms
- Density: 3.93 g/cm^3
- Rotational Period: 24.62 Hours
- Orbital Period: 686.98 Days
Tianwen-2
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| Artist's illustration of Tianwen-2. Credit: CNSA |
Tianwen-2 is planed to be China's first sample return mission. The probe will orbit the asteroid Kamo`olalewa, and collect a sample from it. China is hoping to get a farely large sample, with Tianwen-2 planned to snatch 100 grams of material from Kamo`olalewa. Still, this is a smaller amount than has been brought back by NASA's OSIRIS-APEX (formerly REx) spacecraft. Two-and-a-half years after launch, the probe will return the samples to Earth.
Once the samples are delivered, the probe will use Earth's gravity to fling it into the asteroid belt. On its journey there, Tianwen-2 may make a flyby of an asteroid. Once in the asteroid belt, the spacecraft will enter orbit around the comet 311P/PANSTARRS, and study it for a year or more. This would make it only the second spacecraft to orbit a comet after ESA's Rosetta spacecraft.
The Targets
Kamo`oalewa is in a special orbit around the Sun, never straying far from Earth. The asteroid is believed to be a fragment of the Moon, ejected from one of its many impact craters. Due to its orbit, Kamo`oalewa is sometimes refered to as a "quasi-satellite" of Earth, which is not to be confused with Trojan asteroids.
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| Kamo`oalewa's orbit relative to the Sun and Earth. Credit: HORIZONS/Pheonix7777 CC BY-SA 4.0 |
- Date Discovered: April 27, 2016
- Designation: 469210 Kamo`oalewa (2016 HO3)
- Class: Apollo [NEO]
- Radius: 20.5 Meters (Estimate)
- Rotational Period: 28.02 Minutes
- Orbital Period: 365.97 Days
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| Two Images of comet 311P by the Hubble Space Teliscope. Credit: NASA/ESA/D. Jewitt |
- Date Discovered: August 27, 2013
- Designation: 311P/PANSTARRS
- Class: Encke-Type Comet
- Radius: 240 Meters (Estimate)
- Rotational Period: N/A
- Orbital Period: 1182.76 Days (3.24 Years)
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| Image of Mars from Tianwen-1. Credit: CNSA/CASC |
Tianwen-3 is China's planned Mars sample return mission. The mission will launch an orbiter and lander to Mars. After samples are collected, the lander will launch an accent vehicle to the orbiter. The orbiter will than take the sample, and deliver it to Earth in 2031.
This is a similar timeframe to NASA's sample return mission, which started in 2021 when Perserverance landed on Mars. Both Perserverance and Zhurong launched to Mars in the same window. Unlike Zhurong, Perserverance is built with a sample caching system. Samples drilled from Martian rock are sealed in metal tubes, which Perserverance leaves on the surface of Mars for a future mission to pick up.
China's sample return architecture doesn't include a rover. The lander will drill a sample in its immediate vacinity, then launch it to the orbiter. While neither sample return mission had recieved full funding yet, the first steps have already been taken.
The Target
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| Image of Mars from the Mars Global Surveyor Orbiter. Credit: NASA/JPL/MSSS |
- Date Discovered: Known To The Ancients
- Radius: 3389.5 Kilometres
- Surface Pressure: 0.0099 Atmospheres
- Mass: 6.4169x10^23 Kilograms
- Density: 3.93 g/cm^3
- Rotational Period: 24.62 Hours
- Orbital Period: 686.98 Days
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| Animation of Callisto and Jupiter. Credit: Solar Walk 2/Orchard |
The most ambitous of China's proposed missions, Tianwen-4 would consist of two spacecraft that launch together on a Long March 5 rocket. One would enter orbit around Jupiter, and eventually Callisto. The other would Use Jupiter's gravity to slingshot it to Uranus.
The mission proposal is still fluid, and the final architecture isn't certain. One plan includes a Callisto lander, which would make the mission the first to softly touch down on one of Jupter's moons (Europa Clipper and JUICE will crash into Ganymede).
There is little information available about the Uranus probe concept, but if it happens, it could beat the NASA lead Decadal Survey Uranus orbiter as the first spacecraft to visit Uranus since Voyager 2.
The Targets
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| Cassini image of Jupiter, with Europa's shadow. Credit: NASA/JPL/University of Arizona |
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| Voyager image of Callisto. Credit: NASA/JPL |
- Date Discovered: 1610
- Radius: 1590.8 Kilometres
- Mass: 1.0759x10^23 Kilograms
- Density: 1.834 g/cm^3
- Rotational Period: 16.69 Days
- Orbital Period: 16.69 Days
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