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Mars-moon Exploration with GAmma rays and NEutrons (MEGANE)


Mission Name: Martian Moons eXploration (MMX)
Principal Investigator:Dr. David J Lawrence


The Mars-moon Exploration with GAmma rays and NEutrons (MEGANE) investigation is composed of two sensors, a Gamma-Ray Spectrometer (GRS) and a Neutron Spectrometer (NS). The two instruments share a common data processing unit. MEGANE on MMX has three primary science goals: 1) determine whether Phobos is a captured asteroid or the result of a giant impact; 2) study surface processes on airless bodies in Mars orbit; and 3) support the MMX Phobos sample-return objective. Goal (1) involves determining whether Phobos has a chondritic or achondritic composition, and how depleted it is in volatile materials. Goal (2) requires surface elemental mapping and measurements of surface and subsurface variations in hydrogen. Goal (3) involves assistance with the sample site selection and characterization of the compositional context of the samples. MEGANE will also be making measurements during the flybys of Deimos.

The GRS is based on a 5 cm diameter, 5 cm long high-purity germanium (Ge) crystal in an aluminum enclosure. Low conductivity supports and a vacuum cryostat insulate the crystal thermally from its surroundings. A borated (5% B) plastic scintillator anti-coincidence shield surrounds the apparatus and is read out by a photomultiplier tube. The scintillator actively rejects charged particles within the scintillator and the boron interacts with fast neutrons to act as a detector. Ricor K508N cryocooler maintains the operating temperature at 90 K. GRS is expected to make elemental measurements of H, O, Na, Mg, Si, K, Cl, Ca, Fe, Th, and U.

The NS utilizes two 3He gas-proportional sensors, 5 cm diameter by 20-cm long, mounted in parallel. One sensor tube is covered with a 0.5 mm thick coating of cadmium (Cd) to absorb thermal neutrons, and the other tube is uncoated, allowing all neutrons to be detected by the sensor. Both thermal (energy < 0.4 eV) and epithermal (0.4 eV - 100 keV) are measured by the second sensor, while only epithermal neutrons are measured by the first.

MEGANE was selected as a mission of opportunity for funding by NASA's Discovery program.

Alternate Names

  • MartianMoonseXploration(MMX)/CommonName:MarsmoonExplorationwithGAmmaraysandNEutrons(MEGANE)

Funding Agency

  • National Aeronautics and Space Administration (United States)


  • Planetary Science: Small Bodies
  • 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. David J LawrencePrincipal InvestigatorApplied Physics
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