NASA's announcement that liquid water flows on the surface of Mars has reignited enthusiasm over the possibility of alien life on our planetary neighbor. Liquid water is essential for life to exist here on Earth, and knowing that H20 is flowing on the Red Planet strengthens the odds that extraterrestrial life exists somewhere on Mars, as well. Now more than ever, NASA wants to send probes to the Martian surface to find out for sure.

"Our quest on Mars has been to ‘follow the water,’ in our search for life in the universe, and now we have convincing science that validates what we’ve long suspected," John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate, said in a statement.

Any alien life lurking on Mars will most likely be in the form of tiny microorganisms — not complex biological beings like the ones on our planet. That means finding these aliens is going to be tricky; they will probably be quite small and simple, hiding inside soil samples or hard to reach places. They could look like microbes here on Earth, or they may look like nothing we've ever seen before.

To confirm the existence of such creatures, NASA and other research institutions are developing numerous technologies to search for biosignatures on Mars. A biosignature is any substance with a biologic origin — whether that be a one-million-year-old fossil or a living microbe. Some of these bio-hunting instruments will be incorporated into future spacecraft, like NASA's Mars 2020 rover or the European Space Agency's ExoMars Mission. Others are still in development, looking to be incorporated into a future mission to the Red Planet. But despite this abundance of life detection technologies, it's still extremely difficult to determine if something is — or was — alive on another planet. There is no consensus on the best method for detecting life, and numerous hurdles stand in scientists' way.

To read more, click here.