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Gas Chromatograph / Mass Spectrometer (MODULUS Berenice)

NSSDCA ID: 2004-006A-10

Mission Name: Rosetta
Principal Investigator:Dr. Colin T. Pillinger


The Rosetta MODULUS (Methods Of Determining and Understanding Light elements from Unequivocal Stable isotope compositions) Berenice experiment consists of a gas chromatograph and mass spectrometer. The primary scientific objectives of the experiment are to determine the abundances and isotopic make up of major constituents of the cometary coma, including water, carbon monoxide, and carbon dioxide, and the minor and trace neutral species such as methane, ammonia, and HCN, as well as monitoring the isotopic evolution. Another version of MODULUS (Ptolemy) will be on the Rosetta Lander.

The MODULUS experiment consists of a sample acquisition device, a gas chromatograph, helium carrier-gas supply system, chemical processing modules, a mass spectrometer, and electrical and computer systems. Volatile samples are collected on an exposed substrate pointing in the ram direction. The exposed material is then sealed, the substrate warmed, and the volatiles released sequentially with temperature. The gases are transferred to individual analytical channels and are conditioned and purified by a number of chemical/chromatographic procedures. Purified gas is then admitted to the mass spectrometer for isotopic analysis. The principal isotopic ratios of interest are oxygen 18/16 and 17/16; carbon 13/12; nitrogen 15/14; and D/H. The mass resolution of the spectrometer is approximately m/delta-m = 100.

Alternate Names

  • Rosetta/MODULUS

Facts in Brief

Mass: 3 kg
Power (avg): 5 W

Funding Agency

  • European Space Agency (International)


  • Planetary Science: Small Bodies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Colin T. PillingerPrincipal Investigator

Selected References

  • Wright, I. P., and C. T. Pillinger, Modulus-An experiment to measure precise stable isotope ratios on cometary materials, Adv. Space Res., 21, No. 11, 1537-1545, doi:10.1016/S0273-1177(97)00946-0, 1998.
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