English: To mark 20 years of ESA’s Mars Express, the High Resolution Stereo Camera (HRSC) team has produced a new global colour mosaic: Mars as never seen before. The mosaic reveals the planet’s surface colour and composition in spectacular detail.
Reliably determining accurate surface colours from orbit is difficult due to the variable amounts of dust in Mars’s atmosphere, leading to many mosaic images taking on a patchwork-like appearance; suppressing this effect in image processing usually reduces variations in colour between different parts of Mars. However, to create this mosaic, the HRSC team instead colour-referenced each constituent image using a colour model derived from high altitude imagery, allowing them to preserve colour variations and reveal a far richer colour view of Mars than has been seen before.
This is a simulated view of Mars from a vantage point 2500 km above the colossal Valles Marineris canyon system, with enhanced colour and contrast (at this relatively low altitude, the planet’s polar caps are not visible). It is a composite of red, green and blue filter mosaics with the colour band values stretched individually, and has a spatial resolution of 2 km per pixel (although higher resolution data products are possible and already in the works).
Darker grey-toned areas of Mars represent grey-black basaltic sands of volcanic origin; lighter patches show clay and sulphate minerals; and the large scar across the planet's face is Valles Marineris.
Read more
Alt-text: This image shows the globe of Mars set against a dark background. The disc of the planet features yellow, orange, blue and green patches, all with an overall muted grey hue, representing the varying composition of the surface.