In 2011, the European Space Agency launched Earth's weirdest creature, the tardigrade, into orbit for twelve days on an unmanned spacecraft. And I mean on the spacecraft--scientists attached the organisms to the outside of the rocket to test just how alien-like the very alien-looking tardigrade is.
Of course, it isn't just their looks that make them seem well-suited to the ET lifestyle; as NASA explains, the millimeter-long tardigrades are "known to be able to go for decades without food or water, to survive temperatures from near absolute zero to well above the boiling point of water, to survive pressures from near zero to well above that on ocean floors, and to survive direct exposure to dangerous radiations." Oh, and "they can repair their own DNA and reduce their body water content to a few percent."
Which is why NASA selected this picture of a tardigrade as their "Astronomy Picture of the Day." The image is a color-enhanced electron micrograph.