It’s called “Reddish Bands on Europa“. Sunlight is coming in from the right; the blueish-green sections are water ice, while the red bands that look like a river and its tributaries is ice containing salts of sulfuric acid and magnesium sulfate. The bands do not flow, despite appearances – they are all part of Europa’s frozen outer shell, mostly pure, which has cracked and shifted to expose the darker layer beneath.
It’s centred on 2.9 degrees south latitude and 234.1 degrees west longitude, which (assuming Nasa is just stating the longitude strangely, as usually you only go up to 180 degrees) on Earth would be roughly where the Indonesian island of Siau is located. It covers a square roughly 163 by 167 kilometres, or about twice the land area of Manhattan.
This picture was not taken recently. Galileo – a Nasa probe which studied the Jovian system from 1995 to 2003, the first probe to do so – took the picture above in December of 1997 during a flyby of Europa. This is a colourised version, released this week by Nasa (you can see the original monochrome version here, covering an area almost twice as big), and the colour gives us a striking hint at what might be beneath the surface of the moon. In Nasa’s words:
The reddish material is associated with the broad band in the center of the image, as well as some of the narrower bands, ridges, and disrupted chaos-type features. It is possible that these surface features may have communicated with a global subsurface ocean layer during or after their formation.
Europa is likely the place where we find extraterrestrial life within the Solar System, if we find it at all. Radiation from Jupiter powers plate tectonics which, in turn, leads to volcanism which, in turn, means a steady recycling of minerals and heat throughout the vast ocean that covers it. Deep sea vents there, as on Earth, might be home to simple bacteria-like organisms. Most of what we know about Europa came from Galileo, and it’s remarkable that we gathered so much information that we’re still digging through it today for further clues about what conditions there are like.
And yet. Look at that image. It has the strange shimmer of a still from a VHS tape, and the look of clay under a microscope. It is undoubtedly an alien world, made more alien through the artefacts of colourisation and the passage of time. And it is gorgeous, isn’t it?
The European Space Agency will be launching Juice (the Jupiter Icy Moon Explorer) in 2022, another probe that will fly past Europa (and Ganymede, and Callisto) for further study; Nasa may launch a robotic lander aimed at Europa around the same time.
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