In the early 1700s, several different scientists examining the components of water and water habitats came across a miniscule creature that seemed to float around in many different areas abundant with water. These scientists found that these creatures were really present in many dry places too, but only began to move when hydrated by rainfall or submersion in some body of water.
These creatures were later named tardigrades, and they would become some of the most mysterious and fascinating subjects in modern biology and, though perhaps this may seem unlikely, astronomy. Tardigrades are also called “water bears” because they resemble small, squishy bears with claws and sharp, pointy teeth. In general, most tardigrades survive by sucking up juices from moss, lichens, and algae.
The tardigrade, also called a water bear (NASA Astronomy Picture of the Day).
Though found in some common areas, tardigrades have also been found at elevations of more than 18,000 feet in the Himalayan Mountains, in Japanese hot springs, on the floor of the ocean, and within layers of ice in Antarctica. Tardigrades are an example of “extremophiles,” organism that can survive in extreme environments like these. Our current understanding of tardigrades supports the theory that in order to survive in areas of such extreme pressure and temperature, tardigrades enter a death-like state in these conditions, lowering their metabolism hundreds of times and shedding all water from their bodies. When they are returned to a stable environment, they become rehydrated and continue to live, eat, and reproduce (BBC).
It seemed that these small organisms could survive nearly any climate change in any environment. So, naturally, scientists pushed them further to see if they could survive in the most formidable environment known to mankind – outer space. In 2007, Swedish astronomers launched a satellite into space covered in tardigrades that would, upon leaving Earth’s atmosphere, be freely exposed to the vacuum of space and intense UV radiation from the Sun. The satellite stayed in space for ten days and then returned to Earth. Though many of the tardigrades had gone into a dried-out state, the vast majority of them were revived upon entering water on Earth. A few of them even laid healthy eggs even after being exposed to such a harsh environment.
This experiment could completely change the way that we think about life in space. In fact, many astronomers are exploring the Panspermia Hypothesis, which theorizes whether organisms like tardigrades would be able to survive if a giant impactor – an asteroid, for instance – hit Earth. If tardigrades were able to survive on pieces of Earth that were ejected into space, the existence of life could be spread throughout the Solar System and, potentially, throughout the universe (Smithsonian).
Many aspects of tardigrades are still a mystery to humans. Why did they evolve to be able to withstand several times the amount of temperature and pressure found anywhere on Earth? Where did they evolve, and have they really endured on Earth since the Cambrian period? What can they tell us about the existence of life in space?
Watch this goofy video for more about tardigrades!
More info at New Scientist.
