Test images of Mars acquired by the ExoMars Trace Gas Orbiter’s high-resolution CaSSIS camera on 5 March 2017. The mosaic comprises 40 individual image frames captured using the near-infrared filter. The images were taken just as the orbiter was crossing the boundary between day and night, in the southern hemisphere of Mars. To the top left of the image is the centre of Mellish crater (26ºW, 73ºS). The image scale is 38 m/pixel.