Jupiter's moon Europa
Jupiter‘s moon Europa is one of the most exciting places in the solar system for the possibility of finding extraterrestrial life. This cracked icy globe could provide the right conditions for life to have evolved, in an underground alien ocean.
The Moons of the planets are proving themselves to be just as amazing, dynamic, and totally surprising than any planet could be. For centuries we have studied our own Moon and seen a dead lifeless world, and maybe assumed that the same would be true for all the other planet’s moons. Maybe the moons of our Galaxy are teeming with life systems, orbiting gas giants. Yes astronomers have detected over 600 confirmed planets orbiting other stars and a lot are Jupiter like worlds and larger, but what could be in orbit around these alien worlds?
One of four extremely unique moons of the gas giant, Europa is a vastly different world than Io. Although the same process is going on that gives each moon its amazing characteristics. That process is the effect of Jupiter’s immense gravitational pull, it keeps Io’s volcanoes a third as hot as the surface of the Sun, and it keeps Europa’s interior warm enough for an ocean to exist. This ocean on a body the same size as Earth’s Moon, holds twice as much water than the Earth does in all of its oceans. Europa is keeping the secrets of its alien world locked away under a crust of 5 to 10 miles of ice. But this ice is not inanimate and inert, it is continually shifting, splitting, and moving. Some of the cracks in the ice span 15 to 20 miles wide. The moon is a messy scene of criss cross lines, cracks, splits, and ice ridges that look like they’ve floated into position before freezing.
The photo on the right is a very high resolution Nasa Image of the Conamara Chaos region of Europa showing ice cliffs over 100 metres high, on plates that have broken apart and moved around. The area on the tops of these cliffs has a corrugated pattern, and the base of the cliffs is strewn with debris. The bottom picture is part of Rhode Island at the same scale. The blocks of ice at the bottom of the cliffs are the same size as the houses on the Rhode Island photo.
The second Nasa photo on the left covers an area of 21 miles by 26 miles and shows crustal plates up to 8 miles across that have broken apart, drifted into position, and froze again. This can be seen from cracks that have crossed the boundaries of the plates, but one side of the crack has travelled.
The Nasa image on the right shows a double ridge feature on Europa 1.6 miles wide. It is a fault in the icy crust driven by the huge energy from Jupiter, and visual evidence of the tremendous forces at work on this small frigid satellite.
On Europa specific regions of chaotic terrain are actually named after places in Irish mythology. Rathmore Chaos (Rathmore, Scotland), Narbeth Chaos (Narberth, Wales), Conamara Chaos (Conamara,Ireland), ans Arran Chaos (Isle of Arran, Scotland). Other larger regions of Europa are named after placed in Celtic mythology. It’s these Chaos terrains where a recent discovery has been made of Europa’s liquid water being much nearer to the surface than originally thought, making the chances of extraterrestrial life more likely.
The surface is in constant change and flux, and relatively few meteor craters have been found because any bombardments from space would soon be erased with ice movement. This means that the surface is very young and there are only 7 craters on Europa larger than 20 kilometres in diameter. When a comet or large meteor smashes into the moon, the surface fractures and splits in concentric rings around the impact site. Crater rays can also be seen, similar to crater rays on Earth’s Moon. 
This false colour image shows the impact left when a comet or meteor smashed into the into the frozen satellite, it measures 140 kilometres across (size of Hawaii), and demonstrates how the icy crust ruptured and split in concentric rings around the impact site.
Europa gets wrenched and squeezed by the immense tidal forces at work from Jupiter, and the crust splits and fractures. The same cracks may open and close frequently with the push and pull of the land tides. This keeps the ocean under the crust in a liquid form, and it is thought that the warmer water below wells up through cracks in the ice. But even the massaging from Jupiter’s huge gravity can’t melt the 5 to 10 miles of crust, the bone chilling cold of space is just too much. The temperature at Europa’s surface is around -300 degrees Fahrenheit.
Europa’s orbit around the giant of the solar system is the key to its nature. Our Moon is only about 27% of the Earth’s size, yet it’s gravity still has quite a major influence on our planet in the form of tides. The moon Europa is the same size as our Moon, yet what is pulling on it is bigger than all the planets and moons in the solar system combined. Jupiter could hold 1,317 Earths in its volume. This puts into perspective just how tremendous the forces of gravity are on the ice moon. Europa’s orbit around Jupiter is not a perfect circle but is egg shaped, so it comes in closer at some times than others. This means the strength of the gravitational pull is always changing, it gets pulled and stretched as it orbits close, and returns back to more normal as it orbits further out. So just like when you bend a piece of metal back and forth, heat will build up and the metal will get hot, so the same kind of thing happens in the ice moon.
Jupiter, and Europa (far right) casting a shadow on the planet. Image credit Nasa
What, if anything is in this ocean is any one’s guess and it’s just pure speculation. But it’s thought to be between 100 and 200 kilometres deep, under 5 to 10 miles of ice. There are very few places in the solar system that hold liquid water, and Europa is one of them. Scientists know that where there is water there very well may be life, but if there is alien life in Europa’s ocean it cannot be life that depends on sunlight, as the Sun can never penetrate all that ice. But sunlight does not mean life, it can do very well without it. If life is there it has to be life that depends on chemical processes to survive instead of sunlight. There are plenty of examples on Earth of extremophiles, micro organisms that thrive in extreme conditions the would render other life forms instantly dead. Life has an amazing ability to fit into the smallest of environmental niches, no matter how severe. The best example on Earth is the hydrothermal vents that are found on the ocean floor around geologically active areas, where tectonic plates are moving about. Super heated water spews from these vents at up to 400 degrees celsius, yet they support thriving colonies of shrimps, tube worms, crabs, and bacteria.
They are far from the reach of any sunlight and exist in total darkness, but the bacteria survives from the chemical processes and the bacteria is at the bottom of the food chain. It is possible that Europa has these hydrothermal vents too, due to the pulling and squeezing from Jupiter’s gravity. This creates intense heat inside the small icy moon’s rocky interior, so hydrothermal vents could exist on Europa’s ocean floor spewing out super heated water just like Earth.
Hydrothermal vent on Earth's sea floor
Whatever we find will be amazing, whether it’s life or no life. If we find living things no matter how small, then we can guess that the universe is probably teaming with life. If the place is dead then we have to ask why, and at the same time it would make Earth more special and unique. If living organisms do exist on Europa they would probably be very primitive in nature. Alien Europan octopus is probably out of the question, but the size of the life if it exists really does not matter.
Because Europa is completely covered in ice and reflects most of the sunlight, it is the brightest planetary body in the solar system. This unique world is also one of the smoothest objects too, with no mountains, canyons, or deep craters. Europa is also bathed in deadly radiation from Jupiter’s radiation belts.Europa and Jupiter’s other three moons Ganymede, Callisto, and Io can be seen very easily even in binoculars as small points of light stretched out in a line around Jupiter. Larger telescopes will show Jupiter’s cloud belts and sometimes the moon’s shadows can be seen on the disk of Jupiter.
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