Europa Clipper on a mission to probe an alien water world

The discovery of Jupiter’s four largest moons Ganymede, Callisto, Io and Europa - first sighted by Italian astronomer Gailleo Galilie through a homemade telescope in 1610 - triggered a fundamental rethink in our understanding of the universe. Whilst existing models of the solar system placed the Earth at the centre, Galileo’s observation of moons orbiting Jupiter provided strong evidence that this so-called geocentric model was wrong and marked a key moment in the development of modern astronomy. 

Now, more than four hundred years later, Europa - one of the most promising candidates for life elsewhere in our solar system - is once-again poised to reshape our understanding of the universe, thanks to the arrival later this decade of an advanced spacecraft that will begin to probe and uncover the ice-covered moon’s secrets. 

Thanks to the Galileo mission of the 1990s, scientists have already found strong indicators that Europa may have many of the conditions required to support life: including evidence of a vast sub-surface saltwater ocean as well as organic compounds and energy sources. But NASA’s Europa Clipper mission will be the first to study the moon in detail and determine whether it is indeed habitable. If successful, the search for life on Europa and elsewhere in the solar system will enter an exciting new phase. 

Launched in October 2024 from the Kennedy Space Center aboard a SpaceX Falcon Heavy rocket, the mission is slated to arrive at its destination in around five year’s time, after taking a somewhat circuitous 1.8 billion mile route that swings past Mars (later this month, Feb 2025) and then Earth, using the gravity of each planet as a slingshot to boost its speed. 

On arrival, after using the gravity of Jupiter’s moon Ganymede to help it slow down, the spacecraft will fire its thrusters to get into orbit around Jupiter and in 2031 will begin conducting flybys of Europa that will take it as close as 16 miles from the surface.

One of the key challenges here is presented by Jupiter’s punishing radiation environment, which is the strongest of any planet in the solar system. To help address this, the engineering team has developed a specially designed vault - consisting of 9.2 mm thick sheets of aluminium zinc alloy - to shield the spacecraft’s electronics  from Jupiter’s particle radiation.  To further protect the spacecraft, the team has also devised an elliptical looping flight path that limits its exposure to particularly dangerous parts of Jupiter’s radiation. During this “tour” the spacecraft will make elliptical orbits around Jupiter that bring it close to Europa for 49 flybys.

Each of these flybys will last around one day, and during these short windows of opportunity, Europa Clipper’s full payload of nine scientific instruments - the most sophisticated suite of instrument’s NASA has sent to Jupiter - will set to work.

Powered by two giant solar arrays  - each around 14.2 metres long and 4.1 metres high - this suite of tools will work together to capture data and images relating to Europa’s core, interior, ocean, ice shell, atmosphere and surrounding space environment. Together, these measurements will help scientists figure out whether or not the ice-covered moon is habitable.

One of the key tools here is an instrument that will look directly into Europa’s icy shell: the Radar for Europa Assessment and Sounding: Ocean to Near-surface, or REASON.  Based on technology developed by scientists from the University of Texas for studying Antarctica’s ice sheet, this ice-penetrating radar (which bounces waves off any liquid water under the surface) will send high-frequency radio waves beneath Europa’s crust to measure the thickness and composition of the ice, and search for the ocean that’s thought to lie below.

Other instruments include the Mass Spectrometer for Planetary Exploration/Europa (MASPEX), a complex tool that will analyse Europa’s atmosphere as well as any gases erupting from beneath the surface; and the Surface Dust Analyser (SUDA), which will scoop up micrometeorites ejected from Europa’s surface and explore their chemistry.

Meanwhile, four further tools will study the moon from a distance across a wide range of the light spectrum, from infrared through visible light to the ultraviolet. The Europa Thermal Emission Imaging System (E-THEMIS) will measure how the surface retains heat, which can provide information about the structure and materials present and will also look for hot spots from erupting plumes or underground lakes. The Mapping Imaging Spectrometer for Europa (MISE) will collect infrared light to determine the composition of the surface. The dual-camera Europa Imaging System (EIS) will create a high-resolution map of the surface of Europa, and the Europa Ultraviolet Spectrograph (Europa-UVS) will collect ultraviolet light and create images to help determine the composition of Europa’s atmospheric gases and surface materials, while also searching for evidence of potential plumes erupting from within the moon.

The final two instruments are the Europa Clipper Magnetometer (ECM) - which will hopefully yield information about the size and salinity of Europa’s ocean - and the Plasma Instrument for Magnetic Sounding (PIMS), which will provide information about the plasma environment around Europa.

Europa Clipper’s bundle of advanced scientific tools – arguably the most advanced package of technology ever to be sent to another world – has the potential to fundamentally reshape our understanding of our place in the universe, and to accelerate an exciting new era of planetary exploration.  For now though this complex payload lies largely dormant as it rides out its long and circuitous journey across the gulf of space. 

The discoveries Europa Clipper makes will complement data from the ESA (European Space Agency) Jupiter Icy Moons Explorer (JUICE) mission which was launched in April 2023 and is expected to arrive at Jupiter in 2031.  As previously reported by The Engineer this mission will see a particular focus on Jupiter’s largest moon, Ganymede, and will also explore possible habitats for life.