Image by ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA
The above image of the planet Venus in both night and day. It was taken with the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft. And it is beautiful.
The visible light images show the radiation that gets reflected by the planet’s atmosphere; the infrared part shows the thermal radiation bubbling up from sub-atmospheric depths.
ESA explains in a little more detail:
Venus Express can resolve these structures by use (for the first time from orbit) of the so so-called ‘infrared windows’ present in the atmosphere of Venus. In fact, if observed at certain wavelengths, it is possible to detect thermal radiation leaking from the deepest atmospheric layers, revealing what lies beneath the dense cloud curtain situated at about 60 kilometres altitude.