Does Europa truly have a liquid water ocean beneath its icy shell? Does the ocean spew into space where spacecraft can directly sample it? What materials other than ice are on Europa’s icy surface? How does Jupiter’s relentless radiation affect surface materials? Ultraviolet data will allow scientists to answer some of those questions by identifying Europa’s materials more accurately than ever before.
A prism can separate visible light into a rainbow-like projection of its colors, or wavelengths. Scientists can do the same for ultraviolet light. Europa Clipper’s Ultraviolet Spectrograph (Europa-UVS) collects ultraviolet light with a telescope and separates its wavelengths with an optical grating. Scientists analyze images of that light to identify what substances are made of.Quick Facts
|Operating Power||8.5 Watts|
|Dimensions||35.7 centimeters x 36.2 centimeters x 15.8 centimeters|
|Spectral Range||55 - 210 nanometers|
|Spectral Resolution||<0.6 nanometers (point source), <1.2 nanometers (extended source); resolving power λ/Δλ= 220|
|Spatial Resolution||0.16 degrees (Airglow Port), 0.06 degrees (High-spatial-resolution Port)|
|Field of View||0.1 degrees x 7.3 degrees + 0.2 degrees x 0.2 degrees (7.5 degrees full length)|
|Effective Area||0.6 centimeters² @ 125 nanometers|
|Telescope/Spectrograph||Off-axis primary/Rowland circle mount|
|Detector Type||2D MCP (solar blind), Csl photocathode, cross-delay-line (XDL) readout, full array size 4096 spectral x 4096 spatial x 256 PHD|
|Spectral Cube Size||1900 (spectral) x 1150 (spatial), maximum active area|
|Radiation Mitigation||Contiguous High-Z shielding (4𝛑 sr @detector and electronics)|
How It Works
“Light enters a telescope and bounces off a mirror,” said Kurt Retherford, a staff scientist at the Southwest Research Institute in San Antonio, TX, and principal investigator for Europa-UVS. “The instrument focuses the light through a slit. Then the light lands on a grating that disperses the light across a detector,” he said. “It’s like a digital image you take with a cell phone camera.”
“It’s much like a digital image that you get on your cell phone camera.”
But unlike a cell phone, Europa-UVS sees ultraviolet light, and records more than pictures. Different elements emit and absorb specific wavelengths of light. The instrument records how bright the light is at each of those wavelengths. The resulting data contains the telltale signatures of atoms and molecules. It tells scientists exactly what material the light passed through, or reflected against.
How We'll Use It
Europa-UVS will study the composition and structure of Europa’s atmosphere and surface. It will search near Europa for vapor plumes venting into space from the moon’s liquid water ocean or from reservoirs in its icy shell. Studying that material will be akin to dipping a test tube directly into those bodies of liquid. The instrument will also study the moon’s aurora, its own sort of northern lights.
The instrument will primarily identify relatively simple molecules, such as hydrogen (H2), oxygen (O2), hydroxide (OH), and carbon dioxide (CO2). But Europa-UVS measurements also might be able to detect simple hydrocarbons such as methane (CH4) and ethane (C2H6). Those are building blocks for complex molecules like amino acids — the raw materials of life as we know it. The mission isn’t directly seeking life on Europa, but instead will determine if the moon could support life. Organic molecules in a plume or on the surface would suggest that Europa may have the ingredients for some form of life.Meet the Team
Meet the Team
Tracy Becker is a planetary scientist at the Southwest Research Institute. She's on the Europa-UVS team, and eager to search for plumes at Europa. “Europa has always been one of the most interesting satellites in the solar system. There's tantalizing evidence that it has a subsurface ocean,” she said.
“Europa is one of the most interesting moons in the solar system because of the tantalizing evidence that it has a subsurface ocean.”
To characterize a plume, Europa-UVS could perform a stellar occultation. The instrument will stare at a bright star. Then the spacecraft’s motion causes the plume to pass between the star and the spacecraft. The star’s light will change as plume material intrudes upon the instrument’s line of sight. And that will reveal what materials are present in the plume.