International Space Agencies – Missions and Discoveries

Tardigrade: the water bear

Note4Students

From UPSC perspective, the following things are important :

Prelims level : Tardigrade

Mains level : Not Much


  • On this April 11, the Israeli spacecraft Beresheet attempted to land on the Moon, but crashed on the surface.
  • It was carrying a number of items — including thousands of specimens of a living organism called Tardigrade.

Tardigrade

  • The Tardigrade, also known as water bear, is among the toughest and most resilient creatures on Earth.
  • The Tardigrade can only be seen under a microscope.
  • Half a millimeter long, it is essentially a water-dweller but also inhabits land and, a 2008 study found, can survive in the cold vacuum of outer space.
  • It derives its name from the fact that it looks like an eight-legged bear, with a mouth that can project out like a tongue.
  • Its body has four segments supported by four pairs of clawed legs.
  • A tardigrade typically eats fluids, using its claws and mouth to tear open plant and animal cells, so that it can suck nutrients out of them.
  • It is also known to feast on bacteria and, in some cases, to kill and eat other tardigrades. Although they are famed for their resilience, they are destructible too.
  • Should a human being swallow a tardigrade with her food, her stomach acid will cause the flesh of the tardigrade to disintegrate.

Survival instinct

  • In 2017, a study found that if all other life were to be wiped out by a cataclysmic event — a large asteroid impact, a supernova or a gamma-ray bursts — the tardigrade would be the likeliest to survive.
  • It can endure extreme hot and cold temperature levels.
  • Although the tardigrades on the Israeli spacecraft were dehydrated, the organism is known to “come back to life” on rehydration.
  • In fact, they themselves expel water from their bodies and set off a mechanism to protect their cells, and can still revive if placed in water later.
  • However, there is no evidence of liquid water on the Moon, although there is ice.
  • Without liquid water, it is possible that the tardigrades will remain in their current state, unless future astronauts find them and revive them in water.
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