This picture is a composite of 30 images from ESA’s Huygens probe. They were taken from an altitude varying from 13 kilometres down to 8 kilometres when the probe was descending towards its landing site.
Full story:
http://www.esa.int/SPECIALS/Cassini-Huygens/SEMA6U71Y3E_0.html
Raw images at:
http://esamultimedia.esa.int/docs/titanraw/index.htm