Solar system

Mars was most likely warm and wet about 3.7 billion years ago. But as the planet cooled, the water froze. Remnants exist as ice caps at the poles (as shown here). A recent image of Mars taken by the Hubble Space Telescope shows evidence of water-bearing minerals in large amounts, and scientists say the deposits may provide clues to the planet's water-rich background.

Is there life on Mars?

It has not yet been proven that there is life on Mars. A NASA announcement in 1996 about microscopic life found in a meteorite has failed to convince skeptics, and the search continues.Historical notes

The apparent odd motion of Mars as seen from Earth stumped scientists for centuries, finally leading in the early 1600's to the notion that planets orbited the sun in an elliptical pattern. Percival Lowell, an amateur astronomer who studied Mars into the early 1900s, thought he saw canals that must have been dug by inhabitants. Upon closer examination with modern telescopes and planetary probes, they turned out to be optical illusions.

In 1938, Orson Welles broadcast an Americanized version of a 40-year-old

British novel by H.G. Wells -- The War of the Worlds. The radio drama was perceived by many as a real newscast about a Martian invasion near

Princeton, New Jersey.

Jupiter

The fifth planet from the sun is a huge ball of gas so massive it could hold all the other planets put together. What we can see of the planet are bands of the highest clouds in a thick atmosphere of hydrogen and helium.

Traces of other gases produce the bright bands of color.

The Red Spot

Jupiter's most familiar feature is swirling mass of clouds that are higher and cooler than surrounding ones. Called the Great Red Spot, it has been likened to a great hurricane and is caused by tremendous winds that develop above the rapidly spinning planet. Winds blow counterclockwise around this disturbance at about 250 miles per hour. Hurricanes on Earth rarely generate winds over 180 miles an hour.

The Red Spot is twice the size of Earth and has been raging for at least

300 years. It is one of several storms on Jupiter.

Inside Jupiter

At Jupiter's center is a core of rock many times the mass of Earth. But the bulk of the planet is a thick gaseous murk that appears smeared through a telescope because the planet moves so rapidly beneath. Jupiter's rapid rotation causes it to bulge, making the diameter 7 percent greater at the equator than at the poles.

Around Jupiter

Jupiter has thin, barely perceptible rings and at least 16 satellites. The four largest-- Io, Europa, Ganymede and Callisto -- are called the Galilean moons. They orbit in the same plane and are all visible in a telescope.

JUPITER: RULER OF THE ROMAN GODS, ALSO JOVE

Historical notes

Jupiter was believed by Mesopotamians to be a wandering star placed in the heavens by a god to watch over the night sky. In 1610, Galileo Galilei used a 20x telescope to observe three "stars" around Jupiter. Over several nights he observed these "stars," but each night they were in different positions, leading to his conclusion that they were bodies orbiting the giant planet.

In 1994, astronomers around the world watched as the fragments of comet

Shoemaker-Levy 9 struck Jupiter -- an event that had been forecast. This image shows a bright cloud more than 8,600 miles in diameter caused by the impact.