The Mass Spectrometer measures concentrations of dissolved gases such as carbon dioxide, methane, and hydrogen sulfide that are critical to understanding volcanic, chemical, and biological processes in submarine environments. Carbon dioxide in magma chambers helps drive seafloor eruptions, and, along with methane and hydrogen sulfide, is key to supporting the sub-seafloor biosphere. Until recently, it has been impossible for scientists to measure these gases in situ for long-periods of time. Scientists depended on taking individual samples from vents and seeps, and then analyzing them back in land-based laboratories.

The novel OOI mass spectrometer, developed by Peter Girguis at Harvard University, was installed at a diffuse vent site (MJ03C) on Axial Seamount and at the summit of Southern Hydrate Ridge (MJ01B). In concert, these instruments are providing real-time long-term measurements of gases in both vent and seep environments, providing critical new information about gas evolution in these dynamic systems.

The MASSP instrument class produces two core data products: Level 1 Dissolved Gas Concentrations (DISSGAS) and Level 2 Total Gas Concentration (TOTLGAS). The data for the computation of the L1 core data product are derived from the Residual Gas Analyzer (RGA) integrated in the MASSP instrument. The resulting L1 DISSGAS core data product is calculated from the L0 Mass Spectral Intensities and the sample temperature, also measured by the MASSP instrument, and is composed of the dissolved concentrations (uM) of the individual gases: methane, ethane, hydrogen, argon, hydrogen sulfide, oxygen and carbon dioxide. The L2 TOTLGAS core data product is calculated from the individual dissolved gas concentrations, the inlet fluid temperature, and the pH of the fluid also measured by the MASSP instrument, and is composed of the total concentrations (uM) of the individual gases: hydrogen sulfide and carbon dioxide.

(text and images courtesy of Interactive Oceans)

Data Products

This instrument measures the following data products. Select a data product's name to learn more.

Data Product Code DPS
Suite of Dissolved Gas Measurements (10-20 individual gases) vs. Time MASSPEC

The algorithm code used to generate data products for this instrument is also available in the ion-functions GitHub repository.

Instrument Models & Deployed Locations

The OOI includes the following instrument makes and models for this instrument type. Follow the links below to find out where in the OOI this instrument has been deployed. You'll also find quick links for each instrument to Data portal, where you can plot and access data.

Class-Series Make Model
MASSPA Girguis, Harvard cabled Mass Spec

Primary Science Discipline


Research Themes

Access Data

MASSP on the Data Portal

During ROPOS Dive R1729, a digital-still camera (left), a mass spectrometer (middle) and a fluid- and microbial-DNA sampler (right) were installed in the International District Hydrothermal Field at the vent called El Gordo. A titanium "hat" rests on top of the structure in a tubeworm and limpet patch. Inside the "hat" are temperature probes and intake nozzles for the fluid and DNA sampler. Photo credit: NSF-OOI/UW/CSSF; Dive R1729; V14. Creative Commons License