When a marine biologist visits a coral reef, she might bring containers for collecting samples of water and sediment, nets of various sizes for capturing wildlife, a waterproof tape measure, underwater cameras and microphones — items useful for studying ocean wildlife and the health of marine ecosystems. Because researchers on expeditions can’t bring every scientific tool imaginable, they carry only what they think they’ll need, or what they’ll probably need, to answer specific scientific questions.
For Jupiter’s moon Europa, scientists have some big questions. That’s why Europa Clipper will carry a suite of instruments more advanced and sensitive than anything that’s ever explored this Jovian moon before. Researchers don’t yet know if Europa hosts environments suitable for life to exist, so the spacecraft won’t carry life-seeking instrumentation. Europa Clipper must first answer other questions.
- Does Europa really contain an ocean beneath its shell of ice?
- How deep is the ocean?
- Does the chemistry of the ocean seem friendly for microbes?
- Is Europa’s ice shell tectonically active, allowing the moon’s surface material to make its way to the ocean and vice versa, perhaps enriching the ocean with oxygen-rich molecules from above that could serve as “food” for organisms?
To answer those questions and more, Europa Clipper will be equipped with cameras to map the moon’s surface at high resolution, measure the heights of surface features, produce stereoscopic images, and seek evidence of geologic activity. The spacecraft’s spectrometers will study the composition of Europa’s surface and the particles floating in space above it. An ice-penetrating radar will hunt for water within and below Europa’s icy shell. A magnetometer will measure the strength and direction of Europa’s magnetic field to determine how deep and how salty the ocean is.
The spacecraft’s dust analyzer will analyze tiny fragments of Europa blasted off the surface by micrometeorites. An infrared instrument will measure the moon’s surface temperatures, seeking relatively warm regions where material may have erupted to the surface. Some of the instruments will also seek any material that may be spraying from the ocean into space as plumes. Analyzing that material would enable the spacecraft to analyze Europa’s ocean composition without even landing on its surface.
This is a giant step in our search for oases that could support life in our own celestial backyard. We’re confident that this versatile set of science instruments would produce exciting discoveries on a much-anticipated mission.
A marine biologist on Earth might bring samples from far-flung habitats back to a laboratory for detailed study, but spacecraft rarely return samples to Earth because the fuel needed for the return trip increases a spacecraft’s mass. So Europa Clipper must carry everything it needs for making observations and transmitting those observations back to Earth via radio. It will be outfitted with instruments very carefully chosen to give its mission the best chance of success.
Whatever Europa Clipper reveals, it could change our understanding of the solar system forever. “This is a giant step in our search for oases that could support life in our own celestial backyard,” said Curt Niebur, Europa program scientist at NASA Headquarters in Washington. “We’re confident that this versatile set of science instruments would produce exciting discoveries on a much-anticipated mission.”
Europa Clipper is scheduled for launch in the early 2020s. That’s when the quest to an icy oasis begins.
E-THEMIS
How it will work:
Because objects of different temperatures emit different wavelengths of light, scientists can measure a given object’s temperature by precisely analyzing the light it emits. The Europa Thermal Emission Imaging System, or E-THEMIS will use that principle to produce infrared images of Europa and will allow scientists to measure temperatures on Europa’s surface from a distance.
How we will use it:
The E-THEMIS instrument will study Europa’s surface temperatures to search for signs of recent resurfacing that would result in warm ice at or near the surface. E-THEMIS will also help map the surface roughness, seeking relatively hazard-free regions for a possible future spacecraft to land on Europa.
EIS
How it will work:
The Europa Imaging System, or EIS (pronounced “ice”), will consist of a wide-angle digital camera and a narrow-angle digital camera. Each camera will have an eight-megapixel sensor and will be sensitive to visible wavelengths of light, as well as extending slightly into near-infrared and ultraviolet wavelengths. The narrow-angle camera will be able to pivot 60 degrees on two axes. Both cameras will acquire stereoscopic images, and both will have six filters and will acquire color images.
How we will use it:
The EIS cameras will map Europa at resolutions vastly better than previous missions. Scientists will use EIS to study surface features and how they relate to sub-surface structures, search for signs of recent geologic activity on the moon’s surface and potential plumes venting material into space, and better understand the thickness and structure of Europa’s ice shell. EIS will allow scientists to better measure surface elevations, and color images will provide information about Europa’s surface materials.
Europa-UVS
How it will work:
Just as visible light can be separated into a rainbow-like projection of its constituent colors, or wavelengths, so too can ultraviolet light. Europa Clipper’s Ultraviolet Spectrograph, or Europa-UVS, will collect ultraviolet light with a telescope and spread that light onto a detector. By creating images from ultraviolet light, this instrument will allow scientists to figure out what various atmospheric gases or surface materials are made of.
How we will use it:
The Europa-UVS instrument will observe the composition and structure of Europa’s atmosphere, as well as the composition of the Jovian moon’s surface. It will also search the space around Europa for further evidence that the moon’s potential liquid water ocean is erupting into space in the form of plumes.
Magnetometer
How it will work:
Europa Clipper’s magnetometer instrument will have sensors that measure the direction and strength of magnetic fields in the immediate vicinity of the spacecraft. While compasses and magnetometers are both capable of detecting magnetic fields, magnetometers used for scientific purposes are far more sensitive and precise, allowing scientists to accurately measure magnetic fields and study how they vary with time and location.
How we will use it:
Europa has a magnetic field that is created by the interaction between Jupiter’s much stronger magnetic field and something inside the icy moon. Strong evidence indicates that something is a liquid ocean of salty water. Europa Clipper’s magnetometer should allow scientists to confirm the existence of Europa’s ocean, measure its depth and salinity and determine the thickness of the ice shell above. The magnetometer will also help reveal the source of Europa’s subtle atmosphere and how it escapes over time, along with how its ionosphere interacts with Jupiter’s.
MASPEX
How it will work:
The MAss SPectrometer for Planetary EXploration/Europa, or MASPEX, will collect gases and “bounce” its ions (atoms and molecules missing one or more electrons) back and forth within the instrument. MASPEX will determine the mass of those charged ions by precisely timing their transit through the instrument. In particular, MASPEX is intended to identify dozens of types of hydrocarbons and gaseous molecules, among other materials.
How we will use it:
MASPEX will study gases in Europa’s faint atmosphere for clues about the moon’s surface, its suspected subsurface ocean, and how the ocean and surface exchange material. In addition, the instrument will study how Jupiter’s radiation alters chemical compounds on the moon’s surface. MASPEX will also analyze any plume material that may have vented into space from ice-embedded liquid reservoirs or from Europa’s suspected subsurface ocean.
MISE
How it will work:
The Mapping Imaging Spectrometer for Europa, or MISE (pronounced “mize”), will collect reflected infrared light and separate it into its various wavelengths. Like a visible light camera, MISE will produce pictures. But unlike a visible light camera, the pictures will show the composition of surface materials, not just shape and color, because the amount of light reflected at each infrared wavelength depends on what a surface is made of.
How we will use it:
The MISE instrument will map the distribution of ices, salts, organics, and the warmest hotspots on Europa. These maps will help to determine if the moon’s suspected ocean is an environment suitable for life, and also help understand Europa’s geologic history.
PIMS
How it will work:
Europa Clipper’s Plasma Instrument for Magnetic Sounding, or PIMS, will have four sensors called Faraday cups. These sensors will measure the electrical current produced by plasma (charged particles) as it strikes a detector plate inside each sensor. The Faraday cup sensors will carefully measure the characteristics of the plasma including its density, temperature, and velocity.
How we will use it:
Jupiter’s magnetic field washes over Europa and produces an induced magnetic field, which carries information about the moon’s ice shell thickness, ocean depth, and ocean salinity. But Jupiter’s magnetic field also transports a hot soup of charged particles (ions and electrons) called plasma from the volcanic moon Io and elsewhere to Europa, where the plasma influences the induced magnetic field. Scientists will use PIMS to study the density, energy and flow of plasma around Europa to better understand what the magnetic field is telling us about Europa’s suspected subsurface ocean.
REASON
How it will work:
Europa Clipper’s radar instrument is called Radar for Europa Assessment and Sounding: Ocean to Near-surface, or REASON. The instrument will send radio waves deep into Europa’s ice, where they will bounce off subsurface features and return to the spacecraft. By recording slight differences in the signal’s arrival time back at the instrument, REASON will create pictures of the ice layer’s internal structure.
How we will use it:
Depending on their wavelength, radio waves can either bounce off or penetrate different materials. REASON will use high frequency (HF) and very high frequency (VHF) radio signals to penetrate up to 18 miles (30 kilometers) into Europa’s ice to look for the moon’s suspected ocean, measure ice thickness, and better understand the icy shell’s structure. The instrument will also study the elevation, composition, and roughness of Europa’s surface, and will search Europa’s upper atmosphere for signs of plume activity.
SUDA
How it will work:
When microscopic dust enters Europa Clipper’s SUrface Dust Analyzer, or SUDA, it will pass through a series of grids that repel unwanted plasma particles and measure the dust’s speed and direction. At the back of the instrument, the dust will strike a target plate and disintegrate into smaller, ionized components, which will be pulled to an ion detector that will tell scientists what the dust was made of.
How we will use it:
Microscopic meteorites strike Europa and eject dust-size pieces of the moon’s surface into space, where SUDA will scoop up the particles to reveal the moon’s surface composition. Knowing the speed and direction the dust grains were traveling will help scientists pin down the dust’s origin from Europa’s surface. And if Europa is found to be venting material into space from a subsurface reservoir or ocean, SUDA will analyze that material to help determine whether Europa has environments where life could exist.