Europa Remains the Highest Priority Target for a Future Mission

The icy moon Europa is possibly the most tormenting destination in our solar system. Researchers have been trying for years to kick start a mission to Jupiter’s most mysterious moon, with very Earth-like apprehensions over costs keeping missions stranded until now.

The European Space Agency’s determined mission to Jupiter, JUICE, will visit its fire-and-ice moons – volcanic Io, icy Europa, giant Ganymede, and cratered Callisto – in the 2030s. But it will only deliver a sight of Europa’s surface from a couple of close flybys. With the declaration of the NASA-led Europa Clipper mission, now it looks like a much closer review of Europa is on the cards.

It’s hard to exaggerate the excitement among planetary researchers, after so many years of waiting in the wings while all eyes were on Mars. This is really a quest to comprehend what makes a world liveable.

A Watery World

Europa is the smallest and flattest of the four Galilean moons. At 1,940 miles across, it is approximately a quarter of the size of Earth, made of a mixture of ices and rocks. When the Galileo spacecraft hovered over Europa in the 1990s, it exposed proof of a global sub-surface ocean: vast, deep, dark waters concealed underneath the icy surface.

The water doesn’t freeze totally because it’s constantly pressed by powerful tidal forces as the moon circles around Jupiter once every 3.5 days. What’s more, the ocean is supposed to be in direct contact with the surface ices and the moon’s silicate mantle, which brings together all the essential components for a habitable environment: liquid water, a source of energy, and a source of minerals/nutrients. We know that life on Earth can exist in even the most thrilling environmental circumstances (for example, bacteria recognised as extremophiles), so maybe – just maybe – Europa’s concealed ocean could sustain life.

What to search for

Neither JUICE nor Clipper will reach the surface or the ocean underneath – that’s too great a technological challenge for now. But if liveable circumstances for life are found beyond Earth, chiefly somewhere as far from the Sun as Jupiter and its moons, this could mean that liveable circumstances are common all over the cosmos.

We must start to discover Europa via orbital reconnaissance: to picture and perform spectral study of the composition and geology of the surface, and the radiation, magnetic, electric and plasma fields that sweep across it. With ice penetrating radar we can study through the icy crust, even as far as the hidden ocean to comprehend the forces that formed this icy world.

Europa’s cracked and broken surface is physically quite young, and comparatively crater-free. The structures that the Galileo probe saw from orbit propose freeze-melt procedures that trap icy burgs into frozen seas, producing the scarred patterns known as chaos terrain. Dark parallel ridges criss-cross the bright planes, probably due to tectonics or other geologic processes.

Most astonishing was Hubble’s observations in 2012, which presented proof of huge plumes or geysers erupting tens of kilometres over Europa’s south pole, possibly contributing to a very thin atmosphere. If we could directly sample those trails we might just get a hint of the composition of the deep ocean.

Sooner Rather Than Later

So for all these details and more, Europa remains the uppermost significant target for a future mission. That there are two missions to the Jupiter system stems from years of study within NASA and ESA. At one point a joint mission, the Europa-Jupiter System Mission, was scheduled but was not taken onward due to funding restrictions.

Today, JUICE is full-steam ahead, the project having passed through a full study and definition phase towards now constructing the spacecraft. If all goes to plan it would launch in 2022 and reach Jupiter in 2030. After two years of numerous fly-bys studying Jupiter, its moons, rings and magnetosphere, it will become humanity’s first orbiter of an icy moon, targeting Ganymede in late 2032. If NASA’s newly declared funding is confirmed Europa Clipper may advance even faster, using a new rocket (the Space Launch System) to propel it in the direction of Europa in only a few years, possibly arriving just before or even at the same time as JUICE.

Clipper will perform several flybys of Europa (maybe 45 or more over three years) without entering orbit directly, but will deliver the high-resolution scouting essential to eventually choose a landing site for some future robotic voyager. Though future landing mission is beyond the finance horizon right now, it’s exciting to think that we’ll one day see pictures from that icy and harsh environment, with Jupiter up in the air in the black skies above.

This Article was originally published in IFLScience.


Space Exploration

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