A still more glorious dawn awaits
Not a sunrise, but a galaxy rise
A morning filled with 400 billion suns
The rising of the milky way

-Carl Sagan

When you look up at the sky at night 400 billion stars blink at you. Well, that is if you live in podunk nowhere with minimal light pollution but you get the idea. Its big, the Milky Way is big. What are the chances that life exists outside our own little blue whats-it? depends who you ask but if we look to our closest neighbors it might cast a little optimism into your heart.

Mars

Of course, Mars makes number one on the list of alien destinations. Of the planets in our solar system Mars is the most earth-like.  In fact, many scientists would put their money on the odds that life does or has existed on Mars. Recent evidence shows that liquid water has flowed across the surface of Mars within the last ten years. This makes it likely that liquid water exists under the planets crust, and maybe in it life.

Europa

Europa, Jupitors sixth moon, makes the list, surprising no one. A thick layer of ice covers the surface of the moon, giving rise to speculation that a vast ocean lies below the surface. Atlantis maybe? Probably not. But the possibility of microbes is certainly there.

Titan

Titan is the largest of Jupiter’s moons, and the only non-planet satellite with a known atmosphere. Further, other than Earth, Titan is the only object that has stable confirmed surface water. Even lakes can be seen on the surface. Although, water isn’t the only thing in those lakes. Vast quantities of hydrocarbons mingle in the lakes on Titan. Many believe that similar hydrocarbons may have been responsible for the first life on Earth.

Enceladus

Enceladus, the sixth-largest moon of Saturn, and it can fit lengthwise into the United Kingdom. But, size isn’t everything in the search for aliens. Enceladus is one of three known objects outside earth that have documented volcanic activity. But, even better that volcanic activity is mostly water. Which means that an ocean likely exists below the icy surface.

Ganymede

Ganymede is yet another Jupiter moon. It is the largest of the moons and is the largest moon in the solar system. The surface is mostly silicate rock and water ice. Researchers believe that a saltwater ocean lies about 200km under the surface in a pocket between layers of ice. Much like the other close Jupiter moons, Ganymede is warmed by tidal heating. This creates under ice currents that can remain liquid despite being sandwiched between layers of ice, and even creates pockets of surface water.

Callisto

Callisto is Jupiter’s second largest moon. Farther away than both Europa and Ganymede Callisto experiences much less tidal heating. However, many NASA experts think that liquid water exists under the surface. Further, Callisto receives remarkably low levels of radiation. In fact, Callisto has long been considered a possible location for a human base.

Gliese 581 d

Gliese 581 d orbits the star Gliese 581, at 20 light-years from earth it is the closest planet that orbits within the habitable planet zone. This is the first real candidate for an “ocean planet,” outside earth of course. Enthusiasts are so keen on the promise of deep habitable water and earth like land masses that they have sent high-power radio transmission in hopes of reaching a hospitable alien race. The message will reach Gliese 581 in 2029. If there are aliens we could receive a response as early as 2049, but probably later if they are a bureaucracy.

Thats it!