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Astrobiology - Europa

As one of the major moons of Jupiter, Europa is thought to be the only other planet or moon in our Solar System to contain liquid water. There are several key pieces of evidence to support this:
  • Presence of a very thin atmosphere containing Oxygen - detected by the Hubble Space Telescope
  • Cracks on the surface of Europa caused by a warmer liquid underneath (Europa also has a lower density than Earth, so material underneath the surface is not solid)
  • Lack of meteorite impact craters indicates active geology
  • Islands of thicker ice resemble that of the Earth's polar caps

The image above shows the "cracks" that provide the best proof of an under the surface activity that can only come from liquid.

This image below shows a close-up of one particular group of "cracks."

This shows that some of the liquid underneath broke through the surface (through some type of volcanic action) only to be frozen into these elevated lines.

A common question at this point will be: Europa is far from the Sun, and the surface is completely frozen, so how can liquid water exist underneath? There are two schools of thought:

  • The Galileo Space Probe detected a magnetic field from Europa, this is more likely due to liquid having a bit of salt, and the core of Europa is still warm enough the magnetism is the result of the dynamo effect
  • The intense gravity from Jupiter causes "tidal flexing" which prevents all liquid accept the surface to freeze

Either way, the evidence for an under surface ocean on Europa is pretty strong.

But what of life?

Until we send another probe to Europa for a more detailed analysis (confirm the magnetic field, spectral analysis and so forth), we can only speculate. However, our discovery on Earth of a new type of life called "extremophiles" has raised hope that life could exist on Europa - albeit a more primitive bacterial type.

One such example of an extremophile is the Black Smoker:

These microbes live at the bottom of the ocean near volcanic vents. What is even more remarkable is that tube worms have been found near these vents. They have special bacteria that converts the hydrogen-sulfide released from these vents into energy. These worms also supply food to a vast, newly discovered ecosystem totally independent from the light and warmth of the Sun.

Off the coast of Mexico, almost one mile down, scientists discovered a lake within the ocean. Comprised of mostly thick brine, this lake produces methane that feeds mussels that outline the lake. The mussels also produce hydrogen-sulfide byproducts that nearby tube worms consume - again all without the light or warmth from the Sun.

The presence of these extremophiles on Earth has given hope for the search for life in our own Solar System - and perhaps the Universe.

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