As India prepares to send astronaut Shubhanshu Shukla to the International Space Station (ISS) aboard the Axiom-4 mission, he won’t be travelling alone. Joining him on this historic journey will be a group of nearly indestructible micro-animals—tardigrades, also affectionately known as ‘water bears’.
Tardigrade aka Water bear Credit: Darron Birgenheier
The Axiom-4 mission marks a milestone in India's space collaboration, with the Indian Space Research Organisation (ISRO) partnering with Axiom Space for the ambitious venture. Set to launch aboard a SpaceX Dragon spacecraft, the mission will see Shukla spend 14 days aboard the ISS, conducting a series of scientific experiments—one of the most fascinating being the Voyager Tardigrades project.
This study aims to explore how these microscopic creatures behave in space—how they revive from suspended states, reproduce in orbit, and how their genes respond to the harsh conditions of microgravity and radiation. The research will compare these spacefaring tardigrades with control samples kept on Earth to better understand the molecular mechanisms behind their remarkable resilience.
The experiment is among seven Indian scientific payloads selected for the mission and could yield vital insights for long-duration human spaceflight—particularly as ISRO gears up for its indigenous Gaganyaan programme, which will send Indian astronauts into space aboard a homegrown platform.
Meet the “Water Bears”
Tardigrades are tiny, segmented creatures measuring between 0.1 and 0.5 mm, although some species can grow up to 1.3 mm. First identified in 1773 by German zoologist Johann August Ephraim Goeze and later named Tardigrada—or “slow walker”—by Italian biologist Lazzaro Spallanzani, these creatures have captivated scientists for centuries.
They are found in some of Earth’s most extreme environments—from mountain peaks and ocean depths to Arctic ice and tropical rainforests. Often residing in mosses, lichens, and soil, tardigrades can survive extremes that would kill most other organisms: dehydration, freezing, boiling, radiation, and even the vacuum of space.
Their secret lies in a survival mechanism called cryptobiosis—a state in which they dry out, essentially halting their metabolism and entering suspended animation until rehydrated.
Tardigrades were first considered for space research in the 1960s, but it wasn’t until 2007 that they actually ventured beyond Earth aboard the European Space Agency’s FOTON-M3 mission. There, they endured the vacuum of space for 10 days and returned alive, reviving with just a few drops of water.
They later flew with NASA’s STS-134 mission to the ISS in 2011 and were famously aboard Israel’s Beresheet lunar lander in 2019, which crash-landed on the Moon. Although recovery was impossible, scientists believe some of the tardigrades might still be intact.
The Voyager Tardigrades experiment on Axiom-4 is a more refined investigation, structured to yield concrete data. Axiom Space notes the study will analyze “revival, survival, and reproduction of tardigrades in orbit,” and delve into their gene expression changes under spaceflight conditions. The findings could lead to new biotechnological solutions both in space and on Earth.
[LEFT] Ax-4 Commander Peggy Whitson, Mission Pilot Shubhanshu Shukla of India, Mission Specialist Sławosz Uznański of ESA/Poland, and Mission Specialist Tibor Kapu of Hungary [RIGHT]. Credit: Axiom Space
For ISRO, the implications are clear. Understanding how tardigrades cope with space radiation and microgravity could unlock methods to protect astronauts on long-term missions, such as to Mars or lunar bases. It might also inspire ways to preserve biological tissues and samples during extended space travel, with potential benefits for medicine and biotech industries back on Earth.
Beyond the lab, tardigrades have achieved cult status. Their charming, lumbering gait and superpower-like resilience have made them mascots of scientific curiosity and creativity. They’ve been featured in T-shirts, cartoons, and even church sculptures. Astrophysicist Neil deGrasse Tyson once called Earth “the planet of the tardigrades,” and in 2025, Milnesium tardigradum was voted The Guardian’s “Invertebrate of the Year.”
As India reaches for the stars, it does so with one of the toughest—and tiniest—companions in the universe. The journey of Shubhanshu Shukla and his tardigrade crewmates may well open new frontiers in biology, space exploration, and the limits of life itself.
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