Europa Clipper: NASA’s Mission To Explore The Mysteries Of The Icy Moon

Europa Clipper Official Artwork (credit NASA)

The Launch and Getting to Jupiter

A SpaceX Falcon Heavy will lift off from LC-39a at the Kennedy Space Center in Florida. This will loft Europa Clipper into space, a mission 11 years in the making. Originally slated to fly aboard an SLS rocket, the launch vehicle was changed to a Falcon Heavy due to concerns over the enormous cost of SLS and the vibrations from the mighty SRBs potentially damaging the comparatively light probe. All three of the vehicles first stage boosters will be expended, an offering to the gods of Delta V to ensure that the probe gets as long as possible around Jupiter (currently anticipated to last 4 years once in orbit). The only other time this has occurred so far is the ViaSat 3 launch way back on May 1 last year!

After launch the probe will be placed on a carefully planned trajectory to take it on a Mars flyby in February of 2025, enabling a gravity assist to ‘slingshot’ it towards Jupiter, a commonly used tactic to effectively get velocity for free (although at the cost of time, SLS would have enabled a direct transfer). It will conduct its second flyby of a planet in December 2026, as it briefly comes home, swinging 3200 kilometres above the surface of Earth, this final assist gives the spacecraft the energy it needs to reach Jupiter.

In April 2030, Europa Clipper will fire its engines for six hours to brake into Jupiter’s orbit - this is unusually long for a probe, however NASA has tested the engines many times to ensure they are up to the job! This process will also include a flyby of Ganymede. It will then use multiple flybys of the Galilean moons to shape the orbit to be in the desired resonance with Europa.

Falcon Heavy launches NASA's Psyche Spacecraft (credit NASA)

The probe's orbit around Jupiter (credit NASA)

The Probe

It was first suggested all the way back in 2013, and has gone through multiple revisions and significant redesigns before arriving at the vehicle we see today. This is the largest probe NASA has ever developed for a planetary mission, with a dry mass of 3241 kilograms (6000 kilograms at launch due to the propellant) and immense solar arrays to collect enough light to meet all its needs all the way out at Jupiter. The probe itself measure 5 metres in height, and 30.5 metres in span once the panels are deployed. It has 24 engines, 9 dedicated science instruments, and gravity/radio science equipment.

Its payload and electronic components will be enclosed in a thick-walled vault, much like NASA’s Juno probe. The walls are made from titanium and aluminium and act as a radiation shield against the high levels of radiation the probe will experience around Jupiter. The walls are made from 9.2mm sheets of these metals, and the whole assembly is bolted to the spacecraft’s propulsion module.

The propulsion module is a cylinder of aluminium 3 meters long, and 1.5 meters wide. It contains the 24 engines and 2750 kilograms of propellant, as well as helium pressurant. It has a 3 meter diameter high-gain antenna, as well as other smaller radio antennas to send and receive commands from Earth through NASA’s Deep Space Network. They can also be used for gravity and radio science investigations, allowing scientists to study Europa’s gravity as the moon orbits Jupiter.

For guidance, navigation, and control, it uses sensors, cameras and other hardware to determine and control its position in space. It has two “star trackers” to work out where it is using background stars. It uses four reaction wheels to stay pointed in the right direction, the 60cm wide steel, aluminium, and titanium wheels spin rapidly like gyroscopes, performing thousands of slews as it orbits Jupiter.

The probe also has pumps which circulate fluids through pipes to all of the spacecraft’s sensitive electronics, caryying heat from hot spots to cold spots, and a radiator to shed heat when needed.

Europa Clipper is encapsulated inside Falcon Heavy's fairing (credit NASA)

Science

The main goal of the mission is to assess Europa’s possibility for holding life beyond Earth. It is considered by many scientists the most promising location to find extra-terrestrial life in the solar system, and Europa Clipper is aimed to determine whether it is capable of supporting life.

Europa shows strong evidence for a deep ocean of liquid water below its thick icy crust, likely containing more water than all of Earth’s oceans combined (around twice as much). It also contains all the essential chemical building blocks and energy sources from deep down on the sea floor. It is also thought that it has been relatively stable for around 4 billion years - plenty of time to develop life!

The spacecraft will perform approximately 50 close flybys of the moon, and with each one will gather measurements on the conditions below the surface of the moon. NASA explicitly states it is not a life detection mission, merely one to determine whether Europa could support life.

It has three main science objectives:

• Determine the thickness and characteristics of Europa’s icy shell, and how the ocean interacts with the surface. Scientists want to figure out whether there is definitely liquid water within and/or beneath the shell. They will also seek to estimate the size and saltiness of the ocean - and whether any of the water makes it all the way through the shell to the top, and whether any material also works its way down through the shell, to the ocean.

• To investigate the chemical composition of the ocean, this will determine whether it has all the ingredients deemed necessary to allow and support life.

• Determine the geology of Europa, studying how the surface of the moon formed and any signs of recent tectonic or plume activity on the surface.

Instruments

The probe has several cameras for a variety of purposes:

• Europa Imaging System (EIS). This is a wide-angle camera and a narrow-angle camera, both with 8 megapixel sensors. They will produce both high-resolution colour and stereoscopic images of Europa, studying geological activity, surface heights, and providing context for other instruments

• Europa Thermal Emission Imaging System (E-THEMIS). This is for thermal imaging, using infrared light to distinguish warmer regions on the surface where water may be near, or erupting from, the surface. As well as this, it is capable of measuring surface texture to gain an understanding of the detail.

It is also equipped with two spectrometers:

• Europa Ultraviolet Spectrograph (Europa-UVS). This is an ultraviolet telescope that will create spectrographs to help determine the composition of Europa’s atmospheric gases and surface materials. Alongside this, it will serach near Europa for any evidence of plume activity.

• Mapping Imaging Spectrometer for Europa (MISE). This will map the composition and distribution of ices, salts, organics, and the warmest hotspots on Europa. These will be incredibly useful for scientists to determine the moon’s geological history and determine whether the ocean they suspect is present has the conditions needed for life.

For measuring the plasma and magnetic field it has two instruments:

• Europa Clipper Magnetometer (ECM). This will observe Europa’s magnetic field and aims to ascertain that the ocean does in fact exist - as well as measuring its depth and salinity, and the thickness of the icy shell. As well as this, it measure Europa’s ionised atmosphere and how it interacts with Jupiter.

• Plasma Instrument for Magnetic Sounding (PIMS). Both Europa’s ionosphere and the plasma trapped in Jupiter’s magnetic field distort magnetic fields near Europa. It will distinguish these distortions from Europa’s own induced magnetic field, which in turn carried information on the ocean below the surface of the moon.

For both radar and gravity measurements:

• It will measure the gravity at various points in the moon’s orbit to show how Europa flexes and this will reveal its internal structure.

• Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). This is an ice-penetrating radar that will probe the shell of the moon for reflections from the moon’s suspected ocean, as well as studying the ice’s structure and thickness. Along with this, it has the capability to study the moon’s surface topography, composition, and roughness.

For chemical analysis it carries two instruments:

• MAss Spectrometer for Planetary EXploration/Europa (MASPEX). This mass spectrometer will analyse gases both in Europa’s thin atmosphere and any plumes the probe finds. It will also study the chemistry of the subsurface ocean, how the surface and water exchange material, as well as how radiation alters the compounds on the moon’s surface.

• SUrface Dust Analyzer (SUDA). Europa is often hit by tiny meteorites, these eject bits of Europa’s surface into space, and any ocean or reservoirs below the surface may vent material into the vacuum of space as plumes. The dust analyser identifies that material’s chemical composition and where it originated from, which will offer clues as to the salinity of any subsurface ocean.

This is certainly a mission to look forward to! Thank you for reading this article by Luke Madgett.