Date: 06 August 2009
Depicts: Simulation of methane concentration in Martian atmosphere with a local source and an atmospheric lifetime of 330 years
Copyright: © 2009 Nature Publishing Group, (from Lefèvre & Forget [2009])

This map shows the column-averaged methane mixing ratio in parts per billion by volume (p.p.b.v) as derived from a global climate-chemical model of Mars. The levels are for a solar longitude L_S of 150° corresponding to late northern summer/southern winter. A local methane source was included, marked by the white square, active for only 60 Martian days around L_S=150°.

The amount of methane released from the source is set to balance the global photochemical loss integrated over the Martian year, with a globally-averaged atmospheric lifetime for methane of about 330 Earth years, and assuming an equilibrium value of 10 p.p.b.v.

The local methane source leaves no apparent mark in the resulting map. Instead the only noticeable feature is the relative strong concentration at high southern latitudes, which is due to the removal of CO₂ from the atmosphere by condensation at the pole.