What are the top three candidates for life outside earth in our own solar system?
What are the Top Three candidates? How about five or ten? Look at our own Solar System, There are 5 top candidates that I'm sure no one would disagree with. They are:
Europa: One of Jupiter's Moons and one of my favorites. With a frozen surface, a possibility of an ocean of liquid water buried underneath, and volcanic activity. Which could provide life supporting heat, as well as important chemicals needed by living organisms. Life could possibly survive by hydrothermal vents, like it does on Earth, and in the film Europa Report. :)
Enceladus: The sixth largest moon of Saturn. This world has been called the most promising canidate for life due to its comfortable temperature and the likely presence of water and simple organic molecules. The surface is 99% water ice, with a possibility of water underneath. The spacecraft Cassini's observations in 2005 show the presence of carbon, hydrogen, nitrogen, and oxygen, all organic molecules presumed to be necessary to develop life.
Io: A moon of Jupiter, one of the few that support an atmosphere. Io's atmosphere contains many complex chemicals that are promising for life. The moon is also one of the most volcanically active worlds in the Solar System. With its surface covered in molten hotspots and constantly being bombarded with lethal radiation, it doesn't sound so pleasant, but I will still keep it on the list.
Titan: Saturn's largest moon has an atmosphere rich in compounds that often mark the presence of living organisms. So, for example Titan's air is rich in methane, which is usually destroyed by sunlight. On Earth there is life that constantly replenishes methane, so it might be similarly responsible for the methane on Titan. The moon was even a place of destination for Ethan Hawke's character, Vincent Freeman, in Gattaca.
Mars: I don't need to tell you about Mars, our next door neighbor. Or maybe you're new here? Mars is the most Earth-like of all the Solar System planets. Its size and temperature (it's freezing) is comparatively similar to our own. There exists large amounts of water ice on Mar's poles and a reasonable possibility of water underneath the surface. Most evidence shows that Mars may have been habitable in the past. Geological features suggest water once flowed across the surface and volcanic activity, now long dead, thrived, recycling chemicals and minerals.
That's our Solar System, our neighborhood. What about the thousands of extrasolar planets being discovered? I'll list a few. The rest you can find here.
Top Extrasolar Candidate:
KOI-1686.01 - An exoplanet with an ESI (Earth Similarity Index) of 0.89, making it the most habitable object of interest to date. The planet orbits a star within the habitable "goldilocks zone" where liquid water could exist.
Gliese 667Cc - Said to be 85% similar to Earth. Gliese 667Cc orbits a star that belongs to a triple star system. The sunsets must look spectacular as envisioned by the artist rendering above. Gliese 667Cc is located in the constellation of Scorpius, 22.7 light years away. It isn't the only planet in this system. This triple star system hosts at least seven planets and at least three of those are rocky planets like Gliese 667Cc.
