A microscopic water creature could live until the end of the Earth. The tiny water bear looks like an eight-legged caterpillar. It is one-tenth of a millimeter long and has a very tough body. It can survive without food for decades, and exist in bitterly freezing and boiling temperatures. Water bears can also survive the pressure of deep oceans, the vacuum of outer space, nuclear war, global warming, or any other extreme events that would kill humans.

Scientists say water bears are so tough that only the Sun boiling all the Earth's oceans would kill them. This will happen in several billion years. A study says complex life is very difficult to destroy and could exist on other planets. It says that because water bears are so tough, it is possible for other tough creatures to be in the Universe. It said there was, "a real case for looking for life on Mars and in other areas of the Solar System".