Views of Venus day and night side
Copyright: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA
This sequence of images was taken by the
Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s
Venus Express spacecraft between 12 and 19 April 2006, during the first
orbit (capture orbit) around the planet.
The images were obtained
at six different time slots and different distances from the planet (top
left: 12 April, from 210 000 kilometres; top centre: 13 April, from 280
000 kilometres; top right: 14 April, from 315 000 kilometres; bottom
left:16 April, from 315 000 kilometres; bottom centre: 17 April, from
270 000 kilometres; bottom right: 19 April, from 190 000 kilometres),
while the spacecraft moved along a long ellipse around Venus. The
separate images can be downloaded here [ VOI_1_12_04_2006_b, VOI_2_13_04_2006_b, VOI_3_14_04_2006_b, VOI_4_16_04_2006_b, VOI_5_17_04_2006_b, VOI_6_19_04_2006].
Each
image is the composite of the day side of Venus (left, in blue, taken
in visible light at 380 nanometres) and the night side (right, in a red
colour scheme, taken in infrared light at 1.7 microns).
The
visible part shows solar radiation reflected by the atmosphere. The
infrared part shows complex cloud structures, revealed by the thermal
radiation coming up from different atmospheric depths. 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.
In the colour scheme of the presented infrared images, the brighter the
colour, the more radiation comes up from the lower layers.
