NASA Chooses Instruments to Determine if Europa Is Habitable — And What is That Brown Gunk?

NASA announced the winners of the science instrument selection process for its mission to study Jupiter’s moon Europa today (May 26, 2015).  NASA officials said the mission “must” determine if Europa is habitable.  Part of that is discovering the nature of the “brown gunk” on Europa’s surface.

Europa project scientist Curt Niebur said they have theories about the brown gunk, but will not know for certain until the Europa mission can provide more information.   It is thought to be residue from the liquid ocean scientists are convinced lies beneath Europa’s icy crust.  The material is thought to make its way to the surface via fractures in the ice just as lava makes its way to the surface of Earth.  If so, studying the gunk will reveal the composition of the ocean.

Observations using the Hubble Space Telescope also recently revealed plumes of material being ejected from Europa.  Little is known of these unpredictable plumes, but some of the instruments announced today will focus on characterizing them and determining their constituents, which will provide more data about what is under the crust.

One message today is that the instruments on this mission, which will make 45 flybys of Europa over a 2.5 year period, will be able to reveal Europa’s secrets without touching down on the surface.   Niebur described two of the instruments – a magnetometer and a series of three Faraday cups – as taking an MRI of Europa’s interior structure.  Using them, scientists will be able to determine the depth and saltiness of Europa’s ocean without “dipping our instruments into the ocean just as a doctor can see what’s going on inside your body using an MRI.”

The number and size of instruments that can be accommodated were determined by their total mass and power requirements.   Out of 33 proposals, nine instruments were chosen. They and their principal investigators are:

• Plasma Instrument for Magnetic Sounding.  Dr. Joseph Westlake, Johns Hopkins University Applied Physics Lab (APL)
• Interior Characterization of Europa Using Magnetometry.  Dr. Carol Raymond, Jet Propulsion Lab (JPL)
• Mapping Imaging Spectrometer for Europa. Dr. Diana Blaney, JPL
• Europa Imaging System.  Dr. Elizabeth Turtle, APL
• Radar for Europa Assessment and Sounding:  Ocean to Near-Surface.  Dr. Donald Blankenship, University of Texas, Austin
• Europa Thermal Emission Imaging System.  Dr. Philip Christensen, Arizona State University, Tempe
• Mass Spectrometer for Planetary Exploration/Europa.  Dr. Jack (Hunter) Waite, Southwest Research Institute (SwRI), San Antonio
• Ultraviolet Spectrograph/Europa.  Dr. Kurt Retherford, SwRI
• Surface Dust Mass Analyzer.  Dr. Sascha Kempf, University of Colorado, Boulder.

An additional instrument was selected for technology development:  the Space Environmental and Composition Investigation near the Europan Surface, led by Dr. Mehdi Benna at NASA’s Goddard Space Flight Center.

Europa stirs fascination because of the possibility that conditions to support life might exist there.  NASA Planetary Science Division Director Jim Green explained that Europa’s salty ocean is thought to have more than twice as much water as Earth’s oceans and “it could be a very habitable place if life indeed started on that body many billions of years ago.”  Niebur stressed, however, that the instruments cannot detect life itself.  They can find “indications” of life, but “we don’t have a life detector.”  In fact, he added, there is not even scientific consensus on what to measure in order to detect life with confidence.

When asked what would happen next if the Europa mission did prove there is life, Green joked “I would immediately retire.”   He went on to say that if there is life is on Europa, then it must be “everywhere” in our galaxy and the universe.  It would be an “enormous step forward” in understanding our place in the universe.

A mission to Europa was the second priority for a flagship planetary science mission in the most recent National Research Council (NRC) Decadal Survey on planetary science.   Returning samples from the surface of Mars got top billing, in part because of the high cost of a Europa mission, then estimated at more than $4 billion.   The report recommended that Europa advocates downsize the mission to make it more affordable, yielding the “Europa Clipper” concept now being used as the baseline design.  Green declined to name a firm cost estimate today, offering only that it is about $2 billion (not including launch), but NASA is not able to commit to a price-tag as this early stage.

Niebur said that NASA plans to spend $110 million over three years to advance the nine instruments selected today at which time they will reassess whether these instruments can be ready in time for launch.

Niebur was asked about any commonality between these instrument selections and what will be carried on the European Space Agency’s (ESA’s) JUpiter ICy moons Explorer (JUICE).  He replied that the two missions are complementary, but have different objectives.  JUICE will study Jupiter’s moons Ganymede and Callisto, and make only two flybys of Europa.  NASA’s mission focuses only on Europa and will make 45 flybys.

Green dodged a question about when the mission will be launched.  The answer involves politics as much as science and engineering.  NASA and Congress both use the NRC Decadal Surveys as their “bibles” on what science missions have the top priority.  Consequently, NASA is focusing on Mars and Europa was not in its budget plans.   Rep. John Culberson (R-TX), who chairs the House appropriations subcommittee that funds NASA, is an ardent Europa supporter, however, and has led efforts to add money to NASA’s budget to get the mission initiated and launched sooner rather than later.  Congress added $75 million in FY2013 (none was requested), $80 million in FY2014 (none was requested) and $85 million in FY2015 ($15 million was requested, yielding a total of $100 million).  The House Appropriations Committee’s recently approved FY2016 NASA budget recommendation is to add $110 million in FY2016 to the $30 million requested (for a total of $140 million) with a directive to launch the mission in 2022 using the Space Launch System (SLS).  NASA insists it does not have the funding in its “outyear” projections
to meet that schedule. NASA Administrator Charlie Bolden typically
says the mission will launch in the mid-2020s.

House appropriators also designated $25 million of the $625 million allocated for NASA’s Space Technology Mission Directorate (a reduction from the $725 million requested) to be spent on icy satellites surface technology and test beds. Green said today that NASA is performing “elementary” studies of landed missions, but NASA first wants the global view of Europa that this flyby mission will provide.  NASA’s Galileo mission sent back “tantalizing” glimpses of Europa’s surface, but not in the detail needed to execute a landing.

From a space policy standpoint, the Europa mission could go down in history as the first NASA space science flagship mission funded primarily by annual congressional direction rather than based on administration requests and long term planning.   NASA officials repeatedly say they cannot plan a program based on a hope that each year Congress will add funding for it, but at the moment they are in that position.

If Europa is to be funded by Congress adding money each year, and it is a zero-sum game where NASA’s total budget does not rise to accommodate the unrequested funding, the question is what other NASA activities will be cut to afford it.  In the FY2016 House Appropriations bill, NASA’s earth science program bears the brunt of cuts to afford Europa and other congressional priorities.  Whether the Senate will follow suit is a significant question.  Senator Barbara Mikulski (D-MD), the top Democrat on the full Senate Appropriations Committee as well as the subcommittee that funds NASA, is an avid earth science supporter.   She may be less willing to cut earth science to pay for a Europa mission.  Whether the two chambers can reach agreement to increase the total amount of money available to NASA instead – eliminating the zero-sum aspects of the equation – involves complicated high stakes budget politics that will play out over the next several months.

Correction:  An earlier version of this article misspelled the name of the Ultraviolet Spectrograph/Europa PI.  He is Kurt Retherford, not Rutherford.