China’s Mars Sample Return mission.
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Details regarding China’s plan to return samples from Mars spotlights the country’s work on planetary protection – not only to protect the Red Planet from hitchhiking Earth microbes but also guard our biosphere and we Earthlings from the prospect of hauling back Mars biology.

The importance of planetary protection in China’s deep space exploration plans is reportedly “fully recognized” as the country moves forward on its Tianwen-3 mission.

Hauling back the goods

Projected to rocket back samples from Mars in the 2030 time period, Tianwen-3 would technologically mirror in many ways China’s Moon sampler probes: the Chang’e-5 near side specimen return in December 2020 and last month’s Chang’e-6’s two-day “grab, stash and go” of lunar far side collectibles.

Tianwen-3 will also build upon China’s successful Tianwen-1 Mars orbiter/lander/rover mission launched in July 2020.

Tianwen-1 Mars mission.
Image credit: Kanyan Xu/COSPAR

That lander/rover combination soft landed on the Red Planet in May 2021. The lander’s Zhurong rover reconnoitered the southern part of the Mars Utopia Planitia.

But hauling back the goods from Mars adds new complexity, as well as how best to safely handle the samples once on Earth.

On-location. Lander and Zhurong Mars rover.
Credit: CNSA/Inside Outer Space screengrab


COSPAR presentation

Research on planetary protection technology in China was highlighted during a special Committee on Space Research (COSPAR) “Planetary Protection Week” held last April.

The event was staged at the Royal Society in London, hosted by the Open University’s Astrobiology research group and funded by the UK Space Agency as part of the International Bilateral Fund. 

Among the presentations, Kanyan Xu of the Laboratory of Space Microbiology, Shenzhou Space Biotechnology Group, Chinese Academy of Space Technology in Beijing, China, outlined planetary protection work in China’s deep space exploration projects.

Image credit: Kanyan Xu/COSPAR

Strict measures

“China fully recognizes the importance of planetary protection in achieving the scientific goals of the Tianwen-3 mission and ensuring the biosafety of the Earth,” Kanyan reported to COSPAR. “Strict forward and backward planetary protection measures will be taken.”

As noted in the Kanyan presentation, the Tianwen-1 Mars mission was China’s first planetary protection Category IV mission.

The Tianwen-1 mission did not carry Mars life detection instruments. It did not come into contact with Martian “special regions,” thus it was classed as a Category IVa undertaking: Category IVa is for lander systems not carrying instruments designed for searching for evidence of extant life on Mars.

China’s Tianwen-1 Mars orbiter.
Credit: CNSA

The term special regions are locales on Mars within which terrestrial organisms are likely to replicate or have a high potential for the existence of extant, now present, martian life forms.

The Category IVa definition calls for bioburden levels on the spacecraft’s surface  restricted to below ≤ [Less-Than or Equal To] 3 × 105 spores with an average of ≤ 300 spores per square meter.

Clarified requirements

Kanyan’s presentation states that China space specialists, for the Tianwen-1 mission, established a planetary protection team and clarified the requirements for planetary protection including bioburden control, probability of Mars impact, organic inventory, etc.

Major planetary protection measures included: cleanroom for assembly, integration, and testing (AIT); microbial examination; cleaning, disinfection and sterilization; recontamination control and organic inventory.

The pre-launch bioassay of Tianwen-1 showed the bioburden level of the probe met the requirements for Category IVa missions, Kanyan noted.

Image shows dozens of individual bacterial cells of Tersicoccus phoenicis. This species has been found in only two places: clean rooms in Florida and South America where spacecraft are assembled for launch.
Image credit: NASA/JPL via Victoria Pearson, Open University

Microbial database

For China’s projected Mars sample return mission, the Kanyan presentation points out that it falls into a Category V effort that designates a restricted Earth return: the outbound leg of the mission needs to meet the requirements of Category IVb – a requirement that translates into missions searching for extant martian life.

In reviewing research on planetary protection technology in China, Kanyan’s presentation explains that a large amount of research has been conducted on planetary protection techniques through both international cooperation and independent study and development.

“Through long-term monitoring and sampling of AIT and launch site cleanroom environments in various parts of China, a microbial database and strain storage center have been set up and can be used for future planetary protection technology development and positive control for space mission,” a presentation chart explains.

Image credit: Kanyan Xu/COSPAR

Portable clean environments

“We have developed operational and data analysis protocols for deep space exploration missions, by studying publicly available documents from NASA and ESA,” the presentation states.

For example, work in China has been done on portable clean environments through cooperation with Thales-Alenia Space Italia (TASI).

Through the collaboration with TASI, China has formed a series of planetary protection documents, especially for cleanroom operations and recontamination control for assembly, integration, and testing activities.

The huge canyon that is Valles Marineris is arguably Mars’ most dramatic landscape and offers a scientific bonanza for future robotic and human expeditions.
Image credit: ESA/DLR/FU Berlin (G. Neukum), CC BY-SA 3.0 IGO

Bioburden, sterilization technologies

Members of China’s planetary protection team have passed training classes on planetary protection, cleanroom operations and recontamination control.

“We have various bioburden reduction and sterilization technologies which can be used for PP [planetary protection] purpose, including dry heat sterilization, UV sterilization, hydrogen peroxide gas sterilization, cold plasma sterilization, alcohol/Isopropanol wiping, and so on,” the Kanyan overview explains.

Furthermore, rapid microbial examination technology has been created to more quickly detect spores, thereby shortening the assembly, integration, and testing of Mars-bound hardware.

Protect the Earth

In a summary slide, the goal of planetary protection, Kanyan concluded, “is not only to protect the effectiveness of research on major scientific issues in deep space exploration, but also to protect the Earth and the safety of human[s].”

Tianwen-1 Mars orbiter/lander/rover mission launched in July 2020.
Image credit: China Aerospace Technology Corporation

It is necessary to take planetary protection measures for ensuring the achievement of scientific goals of deep space exploration missions, Kanyan reported.

“China has complied with the [United Nations] outer space treaty and the planetary protection policies formulated by COSPAR,” the summary slide adds, “and has conscientiously carried out planetary protection work during both lunar and Mars exploration missions.”

International consensus

“Their summary slide says it all, concisely,” said John Rummel, a former and founding chair of the panel on planetary protection of the COSPAR, an international confab of experts.

Rummel previously worked at NASA Headquarters (1986 to 1993 and 1998 to 2008) as the space agency’s senior scientist for astrobiology and as NASA’s Planetary Protection Officer.

Rummel told Inside Outer Space it appears that China is innovating to do the planetary protection tasks more effectively with less of a burden than might otherwise be the case.

“Reaching an international consensus on those requirements, despite a lack of direct collaboration with the United Sates, is precisely the reason that COSPAR maintains a Panel on Planetary Protection,” Rummel said.

Europe’s ExoMars mission.
Image credit: ESA/Mlabspace

Doing all the right things

Also assessing the China COSPAR presentation is Cassie Conley, a former NASA planetary protection officer, the longest-serving scientist in that post to date.

Conley said it’s definitely the case that China says they’re doing all the right things for Mars planetary protection.

Specifically, Conley pointed to use of rapid spore assay and plasma sterilization.

Also, the collaboration with Thales-Alenia Space Italia (TASI) “is a very promising sign, since the same group did a good job with planetary protection for the ExoMars lander/rover. TASI did solid work on ExoMars,” she said.

The European Space Agency’s ExoMars is slated for launch between October and December 2028. That venture via its Rosalind Franklin rover — aims to explore the martian surface in pursuit of evidence indicating past life, as well as hunt for present signs of life on Mars.

Substantial resources

Another encouraging aspect of China’s approach, Conley added, based on the COSPAR presentation, are images that may well show the actual facilities China has built for Mars exploration. “They’ve almost certainly invested substantial resources in planetary protection facilities,” Conley added.

“Two things I’d want to know more about include the actual bioburden numbers for the Mars mission China has already sent, and how they’re implementing ‘UV sterilization,’” Conley told Inside Outer Space.

UV light is easily blocked by very thin layers of material, Conley added, “so it’s not a reliable method for any surface that doesn’t have a mirror-finish, since some of the microbes one worries most about will create caves in metal surfaces to live in.”

Arguably, perhaps a highly beneficial scientific consequence from knowing more detail about China’s Mars planetary protection plans is having NASA experts on this issue work cooperatively with China’s Mars team. Doing so would, however, require a relook at U.S. Congressional restrictions on bilateral US-China collaboration, Conley concluded.



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