An exciting new development in planetary exploration was announced today: NASA has chosen the science instruments which will be included in a new mission to Jupiter’s moon Europa. For those advocating and supporting such a mission, this is welcome news indeed. Europa’s subsurface ocean has become a prime target in the search for possible life elsewhere in the Solar System, and this mission may finally help to answer long-standing questions about this fascinating moon.
“Europa has tantalized us with its enigmatic icy surface and evidence of a vast ocean, following the amazing data from 11 flybys of the Galileo spacecraft over a decade ago and recent Hubble observations suggesting plumes of water shooting out from the moon,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “We’re excited about the potential of this new mission and these instruments to unravel the mysteries of Europa in our quest to find evidence of life beyond Earth.”
The science instruments will provide for an unprecedented study of Europa and its potential habitability; underneath the ice crust is a global ocean of liquid water thought to be similar in composition to Earth’s oceans. Along with a rocky sea floor and energy and chemistry from tidal heating, thanks to Jupiter, Europa is a fascinating world which may be quite habitable by Earthly standards.
Europa Clipper, as it is tentatively being called, is a solar-powered spacecraft which will orbit Jupiter, but make 45 close flybys of Europa over three years, at altitudes ranging from 16 miles to 1,700 miles (25 kilometers to 2,700 kilometers). The instrument payload includes high-resolution cameras and spectrometers, ice-penetrating radar, and a magnetometer. The spacecraft will also look for the elusive plumes of water vapor first tentatively seen by the Hubble Space Telescope in 2012. The brownish “smudges” on Europa’s surface are another prime target of study, as they are thought to be places where water from below has reached the surface through the many cracks in the ice shell, depositing minerals or other material. Regions of “chaotic terrain,” where the ice has been broken and jumbled like pieces of a jigsaw puzzle, are also thought to likely be directly over subsurface hydrothermal vents on the ocean floor. Such vents in Earth’s oceans are oases of a wide variety of life forms.
The mission could launch as early as 2022, or at least in the early-mid 2020s.
Out of 33 proposals, nine were selected to fly aboard the mission. They are:
Plasma Instrument for Magnetic Sounding (PIMS) — principal investigator Dr. Joseph Westlake of Johns Hopkins Applied Physics Laboratory (APL), Laurel, Md. This instrument works in conjunction with a magnetometer and is key to determining Europa’s ice shell thickness, ocean depth, and salinity by correcting the magnetic induction signal for plasma currents around Europa.
Interior Characterization of Europa using Magnetometry (ICEMAG) — principal investigator Dr. Carol Raymond of NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif. This magnetometer will measure the magnetic field near Europa and, in conjunction with the PIMS instrument, infer the location, thickness and salinity of Europa’s subsurface ocean using multi-frequency electromagnetic sounding.
Mapping Imaging Spectrometer for Europa (MISE) — principal investigator Dr. Diana Blaney of JPL. This instrument will probe the composition of Europa, identifying and mapping the distributions of organics, salts, acid hydrates, water ice phases, and other materials to determine the habitability of Europa’s ocean.
Europa Imaging System (EIS) — principal investigator Dr. Elizabeth Turtle of APL. The wide and narrow angle cameras on this instrument will map most of Europa at 50 meter (164 foot) resolution, and will provide images of areas of Europa’s surface at up to 100 times higher resolution.
Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) — principal investigator Dr. Donald Blankenship of the University of Texas, Austin. This dual-frequency ice penetrating radar instrument is designed to characterize and sound Europa’s icy crust from the near-surface to the ocean, revealing the hidden structure of Europa’s ice shell and potential water within.
Europa Thermal Emission Imaging System (E-THEMIS) — principal investigator Dr. Philip Christensen of Arizona State University, Tempe. This “heat detector” will provide high spatial resolution, multi-spectral thermal imaging of Europa to help detect active sites, such as potential vents erupting plumes of water into space.
MAss SPectrometer for Planetary EXploration/Europa (MASPEX) — principal investigator Dr. Jack (Hunter) Waite of the Southwest Research Institute (SwRI), San Antonio. This instrument will determine the composition of the surface and subsurface ocean by measuring Europa’s extremely tenuous atmosphere and any surface material ejected into space.
Ultraviolet Spectrograph/Europa (UVS) — principal investigator Dr. Kurt Retherford of SwRI. This instrument will adopt the same technique used by the Hubble Space Telescope to detect the likely presence of water plumes erupting from Europa’s surface. UVS will be able to detect small plumes and will provide valuable data about the composition and dynamics of the moon’s rarefied atmosphere.
SUrface Dust Mass Analyzer (SUDA) — principal investigator Dr. Sascha Kempf of the University of Colorado, Boulder. This instrument will measure the composition of small, solid particles ejected from Europa, providing the opportunity to directly sample the surface and potential plumes on low-altitude flybys.
As Curt Niebur, Europa program scientist at NASA Headquarters in Washington, noted: “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 will produce exciting discoveries on a much-anticipated mission.”
In addition, the SPace Environmental and Composition Investigation near the Europan Surface (SPECIES) instrument has also been chosen for further technology development. SPECIES is a combined neutral mass spectrometer and gas chromatograph which will be developed for other mission opportunities.
While not specifically a life-detection mission, Europa Clipper will help to answer many of the big questions in terms of the habitability of this ocean moon, and there is the potential for discovering evidence which could be indicative of biological processes, as noted in the press briefing. Europa is also just one of several moons in the outer Solar System now known or thought to have subsurface oceans. If even just one of them has become a home for life of some kind, it would be an extraordinary discovery, one that would suggest that biology is common in the universe, even if in many or most cases, it was simple microorganisms. As the search continues, water worlds like Europa would seem to be some of the most likely places to find it.