Europa: Jupiter's Icy Moon

This moon of Jupiter has plate tectonics.  You can see Europa with binoculars along with 3 other Jupiter moons. Europa’ image taken by NASA Galileo spacecraft ( 1995) is fascinating.  This moon of Jupiter has plate tectonics just like Earth, only it’s ice. Astronomers discovered this when the icy surface was dated to be younger than 90 million years.  Since the Solar System is 4,600 million years old this icy surface must be recycled through geological activity, called subduction.  Dinosaurs ruled the Earth 65 million years ago and Earth went through a subduction of sorts about the same time. A new surface crust is being created by the subduction process.  Cracks and ridges abruptly disappear as one ice shell dives below another.  The planet appears to harbor a deep global ocean with a floating, fragmented, shifting ice shell. Europa is 80% larger that our Moon. It has a diameter of 1,944 miles.  It can easily be seen with binoculars having a brightness Magnitude of 5.0.  (  6.0 is considered normal naked eye viewing) Europa gets 25 times less sunlight than our Moon , plunging its surface temperature to -300F.  There would be not liquid water except for the tidal forces of the mammoth planet Jupiter.  Jupiter’s gravity constantly twists and distorts Europa’s mantel.  Flexing and generating internal heat through friction.  This heat keeps liquid water 15 to 19 miles below the surface.

Can Europa’s oceans support life?

"The under surface ocean is a rich soup of organic chemicals and oxygen."

Europa orbits Jupiter each 3.55 Earth days.  Europa is probably our best discover so far as a possible harbor of life outside Mother Earth.  We have found life in Earth’s oceans near volcanic fissures much like the conditions expected to exist below the ice shells of Europa.  Stay tuned, more discoveries are in the making.

Galileo Galilei discovered Europa on Jan. 8, 1610. It is possible that German astronomer Simon Marius (1573-1624) also discovered the moon at the same time. However, it is Galileo who is most often credited with the discovery. For this reason, Europa and Jupiter's other three largest moons are often called the Galilean moons. Galileo, however, called the moons the Medicean planets in honor of the Medici family. [Photos: Europa, Jupiter's Mysterious Icy Moon]

It is possible Galileo actually observed Europa a day earlier, on Jan. 7, 1610. However, because he was using a low-powered telescope, he couldn't differentiate Europa from Io, another of Jupiter's moons. It wasn't until later that Galileo realized they were two separate bodies.
The discovery of the Galilean moons orbiting Jupiter helped scientists realize that the planets in our solar system, including Earth, revolved around the sun and not the Earth.

Age: Europa is estimated to be about 4.5 billion years old, about the same age of Jupiter.

Distance from the sun: On average, Europa's distance from the sun is about 485 million miles (or 780 million kilometers).

Distance from Jupiter: Europa is Jupiter's sixth satellite. Its orbital distance from Jupiter is 414,000 miles (670,900 km). It takes Europa three and a half days to orbit Jupiter. The same side of the Europa faces Jupiter at all times.

Size: Europa is 1,900 miles (3,100 km) in diameter, making it smaller than Earth's moon, but larger than Pluto. It is the 15th largest body in the solar system, and the smallest of the Galilean moons.

Temperature: Europa's surface temperature at the equator never rises above minus 260 degrees Fahrenheit (minus 160 degrees Celsius). At the poles of the moon, the temperature never rises above minus 370 F (minus 220 C).

Characteristics

A prominent feature of Europa is its high degree of reflectivity. Europa's icy crust gives it an albedo — light reflectivity — of 0.64, one of the highest of all of the moons in the entire solar system.
Scientists estimate that Europa’s surface is about 20 million to 180 million years old, which makes it fairly young.
Observing pictures taken by the Galileo spacecraft, scientists believe Europa is made of silicate rock, and has an iron core and rocky mantle, much like Earth does. Unlike the interior of Earth, however, the rocky interior of Europa is surrounded by a layer of ice that is approximately 62 miles (or 100 km) thick.
Experts also think there is an ocean deep beneath the surface of the moon, and that it is possible this ocean contains some form of life. The possibility that there is extraterrestrial life on Europa has sparked the imaginations of many, and is one of the reasons interest in Europa remains high. In fact, recent studies have given new life to the theory that Europa can support life.
The surface of the moon is covered by a saltwater ocean. And, because the moon is so far from the sun, this ocean is frozen across the surface of the moon.

The surface of Europa is covered with cracks. Many believe these cracks are the result of tidal forces on the ocean beneath the surface. It's possible that, when Europa's orbit takes it close to Jupiter, the tide of the sea beneath the ice rises higher than normal. If this is so, the constant raising and lowering of the sea caused many of the cracks observed on the surface of the moon.
It is also thought that the ocean beneath the surface sometimes erupts through the surface (much like lava erupts from a volcano) and then freezes. Icebergs observed on the surface of the moon may support this theory.

Obtaining samples of the ocean may not require drilling through the icy crust. In 2013, the Hubble Space Telescope identified geysers of water vapor spewing from the moon's south pole. The plumes subsequently disappeared, leading scientists to wonder if the features were a cyclical event.
In 2014, scientists found that Europa may host a form of plate tectonics. Previously, Earth was the only known body in the solar system with a dynamic crust, which is considered helpful in the evolution of life on the planet.
 

Atmosphere

Europa has a tenuous oxygen atmosphere, likely the result of charged particles from the sun hitting water molecules on the moon's surface, breaking the molecules into oxygen and hydrogen atoms. While the hydrogen escapes the moon's surface, oxygen is left behind.

Where life may evolve? 

The presence of water beneath the moon's frozen crust makes scientists rank it as one of the best spots in the solar system with the potential for life to evolve.

"The story of life on Earth may have begun in our oceans, and that's because — of course — if we've learned anything about life on Earth, it's that where you find the liquid water, you generally find life," Kevin Hand, an astrobiologist at the NASA Jet Propulsion Laboratory, said in a video about Europa.
"Hidden beneath Europa's icy surface is perhaps the most promising place in our solar system beyond Earth to look for present-day environments that are suitable for life," NASA officials wrote in a statement. "The Galileo mission found strong evidence that a subsurface ocean of salty water is in contact with a rocky seafloor. The cycling of material between the ocean and ice shell could potentially provide sources of chemical energy that could sustain simple life forms."

Europa jelly

The icy depths of the moons are thought to contain vents to the mantle much as oceans on Earth do. These vents could provide the necessary thermal environment to help life evolve.
If life exists on the moon, it may have gotten a kick from deposits from comets. Early in the life of the solar system, the icy bodies may have delivered organic material to the moon.

Europa comb jelly depicts a hypothetical life-form that could potentially exist in the oceans of Europa. Comb jellies are some of the simplest multicellular organisms that exist on Earth. In fact, jellyfish are actually large species of plankton, referred to as “megaplankton”. Because of this, astrobiologists believe that jelly-like organisms would be among the likeliest life-forms to develop on other worlds. Given the correct environment, theories of convergent evolution predict that such organisms are likely to exist and are likely to display traits, such as bioluminescence, that are analogous to those of similar life-forms on Earth. This image depicts how one might appear from the viewpoint of a submersible vehicle shining its headlamps on it. Also depicted is an environment of biological detritus that would be required to sustain this creature. 

Exploration of Europa

The Galileo mission, launched by NASA in 1989, is responsible for much of the information we have on Jupiter and the bodies surrounding it. It took more than six years for the unmanned Galileo spacecraft to reach its destination. The craft stayed in orbit of Jupiter from December 8, 1995 until Sept. 21, 2003. [Best Jupiter Missions of All Time]

In 2013, the U.S. National Research Council's Planetary Science Decadal Review issued its 10-year recommendation for NASA's planetary exploration program. Exploration of Europa was ranked as the highest-priority mission. Since then, NASA has been working toward a mission to Jupiter's icy moon.