Plan view of the NW quadrant of Gale crater with a methane mixing ratio in the lowest model layer for a time series of steady-state methane release at LS 90° and LS 270° ~1 grid point (2.96 km) NW of the Curiosity rover location for sol 305, which is marked with a white cross. Methane is emitted continuously (steady-state release) from the surface at a flux of 1.8 × 10⁻⁶ kg m⁻² s⁻¹. The methane mixing ratio from 0830 to 1700 is zero. White arrows represent the wind speed and direction. Black contours represent the topography. The methane steady-state release began at 0500 LMST on the sol before. The x-y axis labels distance in km. The color scale shows ppbv CH₄.