If things get pretty ugly here on earth from nuclear devastation or an asteroid impact wiping out every living thing, the chances are these little fellas will be fine. Tadigrades otherwise known as water bears or moss piglets are natures true survivors, infact they are close to indestructable.Water bears are microscopic and can be found often living on lichen and mosses anywhere from the Himalayas, the tropics, the arctic, to deep sea trenches, but their true marvel is their near indestructability. Known as polyextremophiles they can survive temperatures of -273°C, close to absolute zero, temperatures as high as 151 °C, 1,000 times more radiation than other animals such as humans, almost a decade without water , and even the vacuum of space. In an experiment a sample of water bears were sent into space for 10 days and exposed to phenomenal levels of solar radiation and yet on return to earth many were still alive and able to reproduce.
They certainly add credit to the theory of exogenesis and panspermia, that life potentially could be spread by extreme forms of bacteria or oganisims able to survive in space living on asteroids or comets, which then eventually impact on habitable planets allowing them to start a new evolutionary tree of life suited to that environment.
There are also some types of bacteria (extremophiles) which can lay dormant for millions of years and can survive similar conditions to water bears and it's entirely possible that life, although stripped back to it's most basic form can become natures interstellar seeds, an ultimate evolutionary advantage to be able to spread a species to new planets. As we develop the technology and neccessity to begin to colonise other life friendly plants and solar systems, we may realise something like these incredible little creatures may have already bet us to it.
