OSIRIS wide-angle camera image taken on 9 April 2016, when Rosetta was 29.9 km from Comet 67P/Churyumov–Gerasimenko. The scale is 2.86 m/pixel.
The unique viewing geometry is such that the spacecraft is positioned almost exactly between the Sun and comet, revealing characteristics of the surface that cannot be seen otherwise.
More details via the OSIRIS Image of the Day website.