Four hundred kilometres above Earth, aboard China's Tiangong space station, a rice plant is growing inside a box roughly the size of a microwave oven. The Shenzhou-23 crew, which docked with Tiangong on May 25, 2026 after launching from the Jiuquan Satellite Launch Center, is currently running the most ambitious iteration yet of China's two-decade effort to grow food in space. The experiment is designed to complete two full seed-to-seed growth cycles in microgravity, comparing plants grown from Earth-origin seeds against the offspring of rice harvested in orbit during the 2022 Shenzhou-14 mission. The research team, based at the Chinese Academy of Sciences, believes the findings will directly shape how future crews on the Moon and Mars feed themselves.
Why growing rice in space is one of the hardest problems in deep space exploration
The fundamental challenge of deep space exploration is not propulsion or radiation shielding alone. It is food. Missions to Mars, which would take seven months of travel each way, cannot carry enough provisions for the entire journey, making in situ food production a hard requirement. Rice is a candidate crop not just because it is a dietary staple for billions of people but because its life cycle has been studied more thoroughly than almost any other grain. According to theChina Manned Space Agency's official Shenzhou-23 mission page, the crew's science programme includes experiments across space life sciences, microgravity physical science, and space-based cultivation, with rice cultivation among the mission's primary research objectives. Lead researcher Zheng Huiqiong of the Centre for Excellence in Molecular Plant Sciences has framed in-orbit rice production as a direct logistical requirement for crews on long-term deep-space missions rather than a laboratory curiosity.
What China learned from growing the world's first orbital rice seeds in 2022
The current experiment builds on a landmark result from four years ago. During the Shenzhou-14 mission, Zheng's team became the first in the world to take rice through its complete life cycle in space, from seed germination through to harvest, inside the Wentian lab module. A peer-reviewed review of China's space station life science programme published in npj Microgravity formally documents this work, describing how the Shenzhou-14 experiment aimed to decode the molecular basis of microgravity-regulated flowering in both long-day and short-day plants while identifying key genes affected by the space environment. Seeds harvested in orbit were brought back to Earth and bred through three generations in ground conditions, demonstrating stable reproductive capacity. But the research also revealed a troubling side effect: seeds that had been through a space environment showed a severely impaired gravitropic response during germination, lying flat instead of growing upward, what the team described as a form of space syndrome imprinted on the plants by microgravity.
How the Shenzhou-23 experiment tests whether space seeds remember their origins
The most scientifically novel aspect of the current experiment is its design around a specific hypothesis: that plants may carry a form of biological memory of previous space exposure. A 2022 study published in the International Journal of Molecular Sciences, analysing rice metabolomics and proteomics after spaceflight stress, confirmed that exposure to space conditions leaves measurable biochemical changes in returned plants, providing molecular-level evidence that the memory hypothesis is worth testing across generations. The Shenzhou-23 setup therefore runs parallel experiments with two seed types: one set that has never left Earth, and another descended from the rice harvested in orbit in 2022 and bred for three generations on the ground. If the offspring of space-grown seeds prove more adaptable in microgravity, it would suggest that spaceflight leaves heritable biological changes in plant lineages, with significant implications for how future missions select their crop varieties.
Why pollen floats in space and what that means for feeding off-Earth crews
One of the more counterintuitive findings from China's earlier space plant research concerns pollination mechanics. During the 2006 Shijian-8 satellite mission, Zheng's team used real-time microscopic imaging to observe pollen behaviour in microgravity and found that, unlike on Earth where gravity draws pollen down onto a flower's stigma, pollen in space floats freely in the air, with only a fraction landing where it needs to go. This finding, and the broader structural changes microgravity induces in plant cell walls, were independently documented in a JAXA-supported study published in PLOS ONE, which found that microgravity suppresses the formation of structural cross-links in rice cell walls, altering how the plant grows mechanically under weightless conditions. Together, these findings explain why the Shenzhou-23 team selected self-pollinating dwarf rice varieties for the current experiment, removing dependence on gravity-assisted pollination while keeping the plant architecture compact enough for a 20-centimetre-tall experimental module.
How engineers solved the problem of planting seeds in zero gravity
Getting a seed to stay in soil sounds trivial until gravity is removed. In microgravity, scattered seeds do not fall onto a surface but float away, and disturbed soil particles follow them into the air, making conventional planting impossible. Water management presents an equally demanding challenge: droplets secreted by rice leaves in a sealed module do not roll off as they would on Earth, but float within the enclosure, threatening to drown the plants in their own exuded moisture if not actively collected. To address the planting problem, the research team developed a plug-in fixed-planting device, a rigid plate fitted with individual slots into which rice spikelets can be attached with biological glue and then pressed directly into the growing medium. A parallel asexual reproduction track, inspired by ratoon rice farming on Earth, will retain root systems after the first harvest and regrow new shoots from existing stubble, letting scientists compare sexual and asexual strategies across two full orbital generations within a single mission, according to the China Manned Space Agency's mission documentation.
What the Tiangong rice experiment could ultimately mean for Moon and Mars missions
The npj Microgravity review of China's space life science programme notes that the broader goal of the Tiangong plant research series is to identify the adaptive mechanisms plants develop under long-term microgravity, information that would directly inform the design of closed-loop life support and food production systems for crewed lunar and Mars habitats. If the Shenzhou-23 experiment successfully completes two seed-to-seed cycles and confirms or refutes the generational memory hypothesis, it will represent the most detailed orbital study of rice reproduction ever conducted, providing the kind of crop-specific data that ground-based simulations cannot replicate. China has stated a target of landing astronauts on the Moon by 2030, a timeline that makes the question of whether rice can reliably complete its life cycle in space not a long-term research aspiration but an immediate engineering problem the Tiangong rice farm is now actively working to solve.
The box aboard Tiangong is small, the rice plants inside it modest, and the questions they are being asked to answer enormous. Whether crops can adapt across generations to space conditions is precisely the kind of problem that cannot wait until astronauts are already on their way to Mars.
© Copyright 2025 The SSResource Media.
All rights reserved.