Tardigrades: The only creatures that can probably survive in space! 

A wide variety of animals have travelled to space, though not by their own choice. They have been part of space missions to check their resilience in the outer space. Monkeys, apes, dogs, cats, tortoises, mice, rats, rabbits, fish, frogs and even spiders have all boarded spaceflights. Few of them safely returned after a short period but most of them couldn’t make their way back. There is one animal, however, that can survive in space over long periods, observe scientists. Here is all about this microscopic creature with a bear-like structure, known as tardigrade.   

Little water bears 
This close relative of insects and crustaceans was discovered in 1773 by a German zoologist Johann August Ephraim Goeze. He dubbed them as “little water bears” because of the way they walk. The name tardigrade (which translates roughly as “slow stepper”) was given to them a few years later by the Italian priest-turned-biologist Lazzaro Spallanzani. 

They are any of 1,300 species of free-living tiny invertebrates belonging to the phylum Tardigrada. You will find them everywhere: In damp moss, on flowering plants, in the sand, in freshwater, and the sea. Freshwater mosses and lichens are their preferred habitat, hence their nickname, moss piglet. However, they will not be visible to your naked eye - they are mostly about 1 mm (0.04 inch) or less in size. , on flowering plants, in the sand, in freshwater, and the sea. Freshwater mosses and lichens are their preferred habitat, hence their nickname, moss piglet. However, they will not be visible to your naked eye - they are mostly about 1 mm (0.04 inch) or less in size.  mosses and lichens are their preferred habitat, hence their nickname, moss piglet. However, they will not be visible to your naked eye - they are mostly about 1 mm (0.04 inch) or less in size.  

Tardigrades have a well-developed head and a short body with eight legs, each tipped with four to eight claws which help them cling to plant matter, and a specialised mouthpart called a buccopharyngeal apparatus, which allows them to suck nutrients from plants and microorganisms. They do not have any special organs for circulation or respiration and their body cavity is filled with fluid that transports blood and oxygen.   

Tiny and tough  
What is the normal life span of tardigrades? Actually, in reality, tardigrades only have a few weeks of active life. But their most remarkable feature is their ability to withstand extremely tough environments. For instance, tardigrades can go up to 30 years without food or water. They can also live at temperatures as cold as absolute zero or above boiling and in the vacuum of space.  

But what enables such resilience? Well, the credit goes to a unique protein that they posse: Dsup, the short form of "damage suppressor". It protects their DNA from being harmed by conditions such as ionising radiation, which is present in the soil, water, and vegetation. 

Another amazing survival trick, a state of inactivity triggered by a dry environment. The micro-animals squeeze all the water out of their bodies, retract their heads and limbs, roll up into a little ball, become dormant and enter the “tun” state — appearing as a lifeless ball in case of any environmental threat. When conditions improve, they unfurl themselves and go about their business. Amazing, isn’t it? In this state, their metabolism may decline to as little as 0.01 per cent of the normal rate. They can survive in this state for years, or even decades. So, despite their short life span, the interval between the time when a tardigrade is born and when it dies might be very long, if it spends most of that time in this hibernating state. No wonder, they have been on earth for about 600 million years, preceding the dinosaurs by about 400 million years.  

Resilience backed by evolution  
Researchers think the reasons for their resilience may lie in their evolutionary history. Like the other major animal groups, tardigrades originated in the sea. When they began venturing onto land, they evolved the tun state, a way to become dormant when there were chances of becoming dried out. And this inadvertently also made them resilient to other stressors including cold and radiation.