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Mass Spectrometer for Planetary Exploration / Europa (MASPEX)


Mission Name: Europa Clipper
Principal Investigator:Dr. Jack Hunter Waite, Jr.


The Mass Spectrometer for Planetary Exploration / Europa (MASPEX) is designed to sample Europa's tenuous atmosphere o determine the distribution of major volatiles and oxygen compounds in Europa's exosphere and in possible plumes. This will help constrain the composition of the surface and sub-surface ocean. MASPEX is a neutral mass spectrometer.

MASPEX has three components: a gas inlet system, the mass spectrometer, and an electronics box. The gas inlet system provides a high-conductance pathway to a closed-ion source. salts, ions, and radicals adsorb to the walls and do not enter the instrument. The inlet can let in gas from the external environment or calibration gas. A thermalizing chamber slows the incoming gas velocity via multiple collisions with the chamber walls, and a cryotrap uses a cooled (65 K), high-surface-area adsorber to trap incoming gas. The inlet valve is closed at the end of sampling, and the adsorber is heated to release the sample into the closed-ion source. The samples are ionized by the closed-ion source, and a sample is released into the mass spectrometer.

The mass spectrometer uses multibounce time-of-flight optics between two reflectrons. After a number of reflections, set by command, the ions strike micro-channel plate detector, giving the time-of-flight spectrum. The detector comprises three 2-micron pore microchannel plates, each with an active area of 38.5 sq mm, in a Z-stack configuration.

Alternate Names

  • EuropaClipper/MassSpectrometerforPlanetaryExploration/Europa(MASPEX)

Funding Agency

  • National Aeronautics and Space Administration (United States)


  • Planetary Science: Atmospheres
  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Jack Hunter Waite, Jr.Principal InvestigatorSouthwest Research
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