Extraterrestrial Life on Europa
Does this Galilean Moon of Jupiter Harbor Simple Alien Creatures?
Beneath an icy crust, Jupiter's moon Europa may have extensive oceans of water that rival Earth's. Did life develop there?
Europa
Europa is the second of Jupiter's four Galilean moons. It is a ball of icy and rocky materials about the size of Earth's moon. There may also be a small metallic core. The more dense rocky materials sank to the core, leaving the icy materials to dominate the crust and mantle.
Tidal heating from Jupiter warms Europa's interior. Hence beneath the frozen crust lies Europa's mantle containing an ocean of liquid water. Galileo spacecraft images of Europa's icy surface show large structures similar to pack-ice on Earth. The pack-ice is found above frozen seas on Earth, so it indicates that there is liquid water beneath Europa's frozen crust.
Water and Extraterrestrial Life
All the life forms we know on Earth require water for life. The bodies of living creatures contain a large percentage of water in their compositions. Most life forms on Earth will die quickly without water. Life on Earth may well have originated in Earth's oceans.
For these reasons the search for possible extraterrestrial life in the solar system is largely a search for water. For example much NASA research on Mars consists of searching for evidence of past water on Mars to try to answer questions about the possibility of extraterrestrial life on Mars.
Extraterrestrial Life on Europa?
Evidence from space missions to Jupiter and its moons shows that beneath its frozen crust, Europa has much more water than Mars. Europa's icy crust is several kilometers thick. Beneath the crust the liquid water layer may be as much as 100 kilometers (60 miles) thick. If Europa's ocean is this thick, then the total amount of liquid water on Europa rivals Earth's oceans.
No other worlds in our solar system have this much liquid water. Hence scientists speculate that Europa may harbor life. The existence of water of course does not prove that life exists on Europa. It simply opens the possibility.
If life forms easily given the right raw materials and conditions, then there may be extraterrestrial life on Europa. However Europa's oceans may not contain all the raw materials needed for life or life may not form easily. Those are questions that science has not yet answered.
Searching for Life on Europa
To find out if life really does exist on Europa, we need to go look. A spacecraft, probably robotic, would have to land on Europa, drill through several kilometers of ice, and search for signs of life in Europa's subsurface ocean. We do not yet have the technology to conduct this search, but our technology keeps improving rapidly.
When we develop the technology to send this mission to Europa, we may find out if extraterrestrial life exists on Europa.
Further Reading
Chaisson, E, and McMillan, S. Astronomy Today 5th ed., Pearson, 2005.
Zeilik, M. and Gregory, S. Introductory Astronomy & Astrophysics, 4th ed., Saunders, 1998.
Zeilik, M., Astronomy: The Evolving Universe, 9th ed., Cambridge, 2002.
