Context: During Axiom Mission-4, Indian Astronaut Shubhanshu Shukla will conduct experiments on tardigrades’ revival, survival, and reproduction during his two-week stay on the International Space Station (ISS).
Relevance of the Topic: Prelims: Key facts about Tardigrades; Voyager Tardigrades experiment.
What are Tardigrades?
- Tardigrades or water bears/moss piglets are microscopic aquatic animals (about 0.5 mm long) discovered in 1773.
- They are Earth's most durable organisms that have existed for around 600 million years, 400 million years before dinosaurs walked the planet, and survived all the five major mass extinction events.
- They have four pairs of legs, each ending in 4-6 claws, and a specialised mouth to extract nutrients from plant cells, algae, and small invertebrates.
- Tardigrades are ubiquitous, from the highest mountains to the deepest oceans, but are most commonly found in the thin water film on mosses and lichens.
- They can survive extreme conditions including temperatures as low as minus 272.95 degrees Celsius or as high as 150 degrees Celsius; endure ultraviolet radiation of space, and pressures of 40,000 kilopascals (equivalent to what can be experienced at a depth of 4 km under the ocean’s surface); and live after being stored in a freezer for 30 years.
Why are Tardigrades so resilient?
Both anhydrobiosis and cryptobiosis result in the emergence of a durable shrunken state, called tun, in which tardigrades are able to withstand extreme conditions.
- Cryptobiosis: Tardigrades owe their incredible resilience to cryptobiosis. It is a state in which organisms bring their metabolism to a near-complete standstill in the face of adverse environmental conditions.
- Anhydrobiosis: Tardigrades can reduce their metabolism to less than 0.01% of normal, and drop their water levels by more than 95%, a state called anhydrobiosis.
- They produce unique proteins such as cytoplasmic-abundant heat soluble (CAHS) proteins which are key to their resilience. These proteins form a gel-like matrix within their cells, vitrifying and protecting essential cellular components from destruction. This allows them to withstand extreme temperatures, radiation, and the vacuum of space.
Why do scientists study Tardigrades in space?
- Tardigrades have been a part of space missions since 2007. European Space Agency’s Foton-M3 mission, carried 3,000 tardigrades in tun state and the post-return analysis confirmed that many survived space vacuum, and some successfully reproduced despite UV exposure, making them the first animals to survive open space.
- In the ongoing Voyager Tardigrades Experiment, scientists will examine the effects of space radiation and microgravity on tardigrades' biological processes. The primary objective is to identify the genes responsible for making tardigrades resilient. This will help scientists develop strategies to protect astronauts during long-duration space missions, and preserve biological materials for extended space travel.
A better understanding of tardigrades’ survival mechanisms can potentially have several applications: from helping scientists develop more resilient crops to creating advanced sunscreens to preserving human tissues and organs for transplantation.