Analysis of information sources in references of the Wikipedia article "Impatto su Giove del luglio 2009" in Italian language version.
«When first seen close to the limb (and in poor conditions) it was only a vaguely dark spot, I [thought] likely to be just a normal dark polar storm. However as it rotated further into view, and the conditions improved I suddenly realised that it wasn't just dark, it was black in all channels, meaning it was truly a black spot.»