Many think it is the most habitable place in the solar system outside of Earth.
First, it's been believed for a long time that it has a subsurface ocean because of its smooth surface and almost complete absence of craters, obviously there is some process erasing them, and easiest way is if it has a subsurface ocean. Also its interior is heated up by the tidal effects of the other moons of Jupiter acting on it and counteracting the effects of Jupiter. So it is continually being pushed and squeezed which keeps it warm.
But then back in 2009, Richard Greenberg studied processes on the surface of Europa and came to the conclusion that its ocean must be oxygen rich. The ocean is surely not new, and over a period as short as a few million years, he worked out, it would become as oxygen rich as the Earth oceans.
Then also recently they discovered water plumes from Europa, December 2013
Water plumes spark a race to Jupiter moon Europa
Giant Geysers on Jupiter's Icy Moon Europa Mysteriously Disappear
These could possibly be signs of the internal ocean erupting to the surface as "water volcanoes". Or they could be surface features not connected with the ocean. Nobody knows yet.
Many elements and simple compounds detected on the surface. Seems easily to have enough diversity of chemistry for life:
Page on virginia.edu
There is some evidence also about the composition of the ocean itself from studying differences in the chemical signatures of the leading and trailing sides of Europa and studying how the surface of Europa would be affected by sulfur deposited on it from the Io eruptions.
If the reasoning of these researchers is correct, it is chloride rich with sodium and magnesium chlorides like the Earth's ocean (rather than sulfate rich):
So - a salty ocean that might quite possibly be similar in composition to Earth, oxygen rich, the body itself deformed by the other satellites and Jupiter by tidal effects, very probably has hydrothermal vents or similar deep down in the ocean. It's got all the ingredients to be a very habitable place.
But - no detection of life yet. Maybe if we can send a spacecraft to "taste" the plumes and analyse them it might detect biosignatures though? If they do come from deep down.
So - does it have life? Or - I think myself just as intriguing, what if it doesn't have life? What happens to an ocean like this, oxygen rich, left for billions of years, all the conditions for life, does it perhaps get as far as some kind of metabolism, or create chemicals XNA that "sort of replicate but not quite" - if it hasn't quite got as far as life in all those billions of years, it would be fascinating to find out what has happened there in the place of life,
It might just possibly also have life with shared ancestry to Earth way back.
So
Could be any of those. Or perhaps something nobody has thought of yet.
First, it's been believed for a long time that it has a subsurface ocean because of its smooth surface and almost complete absence of craters, obviously there is some process erasing them, and easiest way is if it has a subsurface ocean. Also its interior is heated up by the tidal effects of the other moons of Jupiter acting on it and counteracting the effects of Jupiter. So it is continually being pushed and squeezed which keeps it warm.
But then back in 2009, Richard Greenberg studied processes on the surface of Europa and came to the conclusion that its ocean must be oxygen rich. The ocean is surely not new, and over a period as short as a few million years, he worked out, it would become as oxygen rich as the Earth oceans.
"Richard Greenberg of the University of Arizona has considered three generic resurfacing processes: gradually laying fresh material on the surface; opening cracks which fill with fresh ice from below; and disrupting patches of surface in place and replacing them with fresh material. Using estimates for the production of oxidizers at the surface, he finds that the delivery rate into the ocean is so fast that the oxygen concentration could exceed that of the Earth’s oceans in only a few million years. "
For more details: Jupiter's Moon Europa Has Enough Oxygen For Life
Then also recently they discovered water plumes from Europa, December 2013
Giant Geysers on Jupiter's Icy Moon Europa Mysteriously Disappear
These could possibly be signs of the internal ocean erupting to the surface as "water volcanoes". Or they could be surface features not connected with the ocean. Nobody knows yet.
Many elements and simple compounds detected on the surface. Seems easily to have enough diversity of chemistry for life:
Page on virginia.edu
There is some evidence also about the composition of the ocean itself from studying differences in the chemical signatures of the leading and trailing sides of Europa and studying how the surface of Europa would be affected by sulfur deposited on it from the Io eruptions.
If the reasoning of these researchers is correct, it is chloride rich with sodium and magnesium chlorides like the Earth's ocean (rather than sulfate rich):
Shows the Europa water plumes (which may connect to the subsurface ocean) and Io's "sulfur volcanoes". Sulfur from Io gets deposited on Europa and by looking at how this interacts with the surface the researchers got clues about Europa's subsurface oceans.
A Window Into Europa's Ocean Lies Right at the Surface | Caltech
So - a salty ocean that might quite possibly be similar in composition to Earth, oxygen rich, the body itself deformed by the other satellites and Jupiter by tidal effects, very probably has hydrothermal vents or similar deep down in the ocean. It's got all the ingredients to be a very habitable place.
But - no detection of life yet. Maybe if we can send a spacecraft to "taste" the plumes and analyse them it might detect biosignatures though? If they do come from deep down.
So - does it have life? Or - I think myself just as intriguing, what if it doesn't have life? What happens to an ocean like this, oxygen rich, left for billions of years, all the conditions for life, does it perhaps get as far as some kind of metabolism, or create chemicals XNA that "sort of replicate but not quite" - if it hasn't quite got as far as life in all those billions of years, it would be fascinating to find out what has happened there in the place of life,
It might just possibly also have life with shared ancestry to Earth way back.
So
- Independently evolved life
- No life and only rather simple chemistry
- Complex chemistry that is "almost alive" maybe with recognizable cells for instance, but they don't reproduce exactly. Maybe even larger structures, sort of like stromatolites and corals - but not created by lifeforms, but by this "almost alive" chemistry.
- Shared ancestry at some point in past (including very early shared ancestry but before the "last common ancestor" of all Earth life)
- Mix of shared life and independently evolved life
Could be any of those. Or perhaps something nobody has thought of yet.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
4.8m answer views110.4k this month
Top Writer2017, 2016, and 2015
Published WriterHuffPost, Slate, and 4 moreHuffPost, Slate, Forbes, Newsweek, Business Insider, and Science 2.0