Origins: Fourteen Billion Years of Cosmic Evolution (36 page)

26:
This wide-angle photograph, taken by amateur astronomer Rick Scott in 2003, shows the bright streak produced by one of the meteors observed during the annual Perseid meteor shower in mid-August, a time when Earth encounters more space debris than usual. Moving at many miles per second, each piece of debris plows through Earth’s atmosphere to the point that the meteoroid vaporizes, either partially or totally. In this photograph, the Andromeda galaxy (left of the middle) can be seen at a distance about 1 million trillion times greater than the altitude of the meteor, approximately 40 miles above Earth’s surface.

27:
Saturn, the Sun’s second largest planet, has a beautiful system of rings, photographed in all their glory by the Hubble Space Telescope. Like the more modest ring systems around Jupiter, Uranus, and Neptune, Saturn’s rings consist of swarms of millions of small particles orbiting the planet.

28a & b:
Titan, the largest moon of Saturn, has a thick atmosphere made mainly of nitrogen molecules, but also rich in smoglike particles that permanently block its surface from view in visible light (upper image, photographed by the
Voyager 2
spacecraft in 1981). Observed in its infrared radiation, however (lower image, taken with the Canada-France-Hawaii Telescope at the Mauna Kea Observatory), Titan reveals the outlines of surface features that may well be liquid pools, areas of rock, and even glaciers of frozen hydrocarbons.

29:
In December 2000, as the Cassini spacecraft passed by Jupiter en route to its Saturn rendezvous in 2004, it photographed the outer layers of the Sun’s largest planet. Jupiter consists of a solid core, surrounded by gaseous layers tens of thousands of miles thick. These gases, which are mainly compounds of hydrogen with carbon, nitrogen, and oxygen, swirl in colorful patterns as the result of Jupiter’s rapid rotation. The smallest features visible in this photograph are about forty miles across.

30a & b:
Europa, one of Jupiter’s four large moons, has about the same diameter as our Moon, but its surface displays long, straight lines that may represent worldwide cracks in its icy surface (top panel). Having secured this global view of Europa, the
Galileo
spacecraft went in for a closer inspection (bottom panel) from a distance of only 350 miles. This close-up of Europa’s surface shows ice hills and straight rills, with what may be darker impact craters among them. Speculation runs high that Europa’s surface ice layer, perhaps as much as half a mile thick, may cover a moonwide ocean, capable of supporting primitive forms of life.

31:
During the early 1990s, radio waves from the
Magellan
spacecraft orbiting Venus, which can penetrate the planet’s optically opaque atmosphere, allowed astronomers to produce this radar image of Venus’ surface. Numerous large craters appear in this image, while the broad bright-colored area is the largest of Venus’ highlands.

32
: In 1971, the
Apollo 15
astronauts used the first vehicle on another world to explore the lunar highlands, searching for clues to the Moon’s origin.

33:
In October 2003, two large groups of sunspots, each several times larger than Earth, appeared on the face of the Sun, captured here by amateur astronomer Juan Carlos Casado. Rotating along with our star, these sunspots take nearly a month to cross the sun’s surface and come back around again, typically fading away in about that time span. Sunspots owe their relative darkness to their cooler temperatures (about 8,000˚ F. in comparison to the Sun’s average surface temperature of 10,000˚ F.). The lower temperatures arise from the influence of magnetic fields, which are also associated with violent solar eruptions, capable of emitting streams of charged particles that affect radio communications on Earth and the health of astronauts.

34:
This image of Mars, taken by the Hubble Space Telescope during the planet’s close approach to Earth in 2003, shows the south polar cap (mostly frozen carbon dioxide) at the bottom. At the lower right, the large circular feature is called the Hellas impact basin. Many smaller craters dot the lighter-colored Martian highlands, while the large darker areas are the lowlands of Mars.