Simulating weather, climate, and atmospheric chemistry on Mars

Planetary aeronomy
BIRA-IASB developed a weather and climate model for Mars, similar to weather forecast models on Earth, to simulate the atmospheric chemistry on Mars. The destruction of the more abundant carbon dioxide (CO2) and water vapour (H2O) molecules in the Martian atmosphere by sunlight leads to the formation of minor species such as oxygen (O2), carbon monoxide (CO), ozone (O3), and hydrogen peroxide (H2O2). The BIRA-IASB model is able to simulate the concentrations and variations of these molecules with good precision. The model will support the data analysis of the NOMAD instrument on the ExoMars Trace Gas Orbiter.

The GEM-Mars model

To study the Martian atmosphere, large three-dimensional computer models are required, incorporating atmospheric dynamics and chemistry, similar to large weather and climate models on Earth. BIRA-IASB developed such a model, starting from a Canadian weather model for Earth. This model, GEM-Mars, is only the second of its kind in the world.

Mars atmospheric chemistry

The atmosphere of Mars consists of 96% carbon dioxide (CO2). The north polar ice cap releases water vapor (H2O) every year during summer.

The chemical interactions between the photolysis products of CO2 and H2O lead to the formation of other species, such as ozone (O3) and hydrogen peroxide (H2O2). Both CO2 and H2O on Mars undergo a complex cycle as they can be frozen into ice clouds or surface ice.

Models for Mars need to include all these complicated interactions.

Recent results and future plans

An extensive evaluation of the GEM-Mars model was performed by comparing to the most complete datasets for the species that have been observed on Mars with wide coverage:

  • CO2
  • CO
  • H2O
  • H2O2
  • O3
  • airglow from O2

The results are very good and bring GEM-Mars to the state of the art. Now the model will be applied for the analysis and interpretation of the observations from the NOMAD instrument on the ExoMars Trace Gas Orbiter, which started its investigation of the composition of the Mars atmosphere in April 2018.

Variation of ozone on Mars over 1 Mars year: observations from MARCI on the NASA MRO satellite (top) compared to the GEM-Mars simulation (bottom). Units are µm-atm. Data provided by R.T. Clancy, Space Science Institute, USA.
Variation of ozone on Mars over 1 Mars year: observations from MARCI on the NASA MRO satellite (top) compared to the GEM-Mars simulation (bottom). Units are µm-atm. Data provided by R.T. Clancy, Space Science Institute, USA.
Distribution of H2O2 on Mars around fall equinox, as simulated by GEM-Mars (column-integrated volume mixing ratio, parts per billion). The simulated values correspond well to observations performed from a telescope based on Hawaï by Thérèse Encrenaz (Observatoire de Paris, France). The map is centered on the Tharsis region with 4 major volcanoes.
Distribution of H2O2 on Mars around fall equinox, as simulated by GEM-Mars (column-integrated volume mixing ratio, parts per billion). The simulated values correspond well to observations performed from a telescope based on Hawaï by Thérèse Encrenaz (Observatoire de Paris, France). The map is centered on the Tharsis region with 4 major volcanoes.