Figure 25. Saturn Small Moons
The satellites shown here range in size from about 20 to 200 kilometers. They lack sufficient gravity to enforce a spherical shape.
Figure 26. Uranus Rings
This infrared image, taken at a wavelength of 2.2 microns, reveals several distinct rings encircling the planet. The isolated bright spot is the moon called Miranda.
Figure 27. Phobos
This curiously potatolike cratered inner moon of Mars has an average diameter of 22 kilometers and an orbit period of about eight hours.
Figure 28. Deimos
The outer moon of Mars has an average diameter of 13 kilometers and an orbit period of thirty hours.
Figure 29. Mars Surface by Firing 1
The view from the Viking 1 Lander on the surface of Mars, in 1977, shows a rocky landscape and a ruddy sky. The lander in the foreground has its meteorology arm extended.
Figure 30. TlTAN DISK
The largest moon of Saturn, with its intriguing features photographed by the Cassini orbiting space probe in 2005.
Figure 31. TlTAN COAST
Showing icy highlands with dry rivers and what appears to be the shoreline of a vanished sea, as seen by the Huygens descent probe from an altitude of about 10 kilometers in 2005.
Figure 32. Sagittarius Stars
The Spitzer Space Telescope turned its gaze toward the constellation Sagittarius. Its infrared camera was able to penetrate the obscuring curtains of gas and dust for a thrilling look at the crowded center of the Milky Way Galaxy.
Figure 33. SETI SPECTRUM
A graph of the natural radio background noise over a wide range of frequencies. At lower frequencies (left), charged particles in our galaxy emit increasing noise. At higher frequencies (right), the intrinsic quantum noise of any radio receiver increases. Between them is a relatively quiet "window," where interstellar hydrogen (H) and hy-droxyl (OH) emit radio energy at discrete frequencies. This plot does not include radio emission from molecules in the Earth's atmosphere.
Figure 34. Simulated SETI Signal
The search for extraterrestrial intelligence includes the monitoring of stars at many radio frequencies simultaneously over time. A successful detection might resemble this signal, which actually came from the Pioneer 10 spacecraft in the outer solar system. The drift in frequency over time shows that the source is not rotating with the Earth, but is of extraterrestrial origin.
Figure 35. The Cretaceous-Tertiary Record in the Rocks at Gubbio
The evidence for the event that caused the extinction of the dinosaurs sixty-five million years ago was discovered in this sequence of sedimentary strata from Gubbio, northern Italy. The pale limestone layers at the lower right were deposited in the Cretaceous period, when dinosaurs ruled the Earth. The darker limestone layers at the upper left are from the subsequent Tertiary period, when they had become extinct. In between, the diagonal layer of black clay contains the worldwide iridium-rich fallout of debris from the crater excavated by the collision of an asteroid or comet. This layer is found everywhere on Earth where rocks of this age are exposed. The edge of a coin at the top is for scale.
Figure 36. Cretaceous-Tertiary Impact
Don Davis, one of the greatest painters of science-based art, takes us to the panicky last second of the age of the dinosaurs. An asteroid or comet some 10 kilometers in diameter plunged through the shallow ocean near what is now Yucatan in Mexico, igniting global wildfires and producing a dense cloud of smoke and dust that darkened and froze the surface of the Earth.
Carl Sagan
