The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
Go to topicThank you for liking
You have already liked this page, you can only like it once!
The far left image shows the bright-dark boundary region on Saturn’s moon Iapetus at far-ultraviolet wavelengths, viewed by Cassini's ultraviolet imaging spectrograph on 10 September 2007.
These wavelengths represent reflected solar light and indicate where the surface is brightest and highest in water ice abundance. (Red indicates the brightest regions, purple the darkest.) The bright 'Voyager Mountains', part of the equatorial ridge, are seen as bright spots against a dark background. The dark material that covers one hemisphere of Iapetus is indicated in purple and is seen on the right side of this image.
The middle image is a color composite: blue-green (longer ultraviolet wavelengths) indicates where the surface is bright and probably richest in water ice. Red (short ultraviolet wavelengths) indicates where the surface is low in water ice and relatively high in dirty material. The sky background is also bright at these wavelengths, making the limb, or edge, of Iapetus where the surface is dark indistinguishable from the sky background.
The image on the right, taken by the imaging science subsystem, is for reference, with the regions observed by Cassini’s ultraviolet imaging spectrometer outlined in red.