The Mariner 4 probe was launched in 1964 and traveled toward Mars. It was the first satellite to take up close pictures of another planet.
Credit: NASA

On Earth, the blue and green planet of our solar system, we are celebrating Red Planet Day today, November 28. The red planet is a nickname for Mars, the fourth planet from the sun. On November 28, 1964, NASA launched the first mission toward Mars, with the Mariner 4 probe. We call it “the Red Planet” because the surface of Mars has a reddish color due to the weathered iron-rich minerals present in the Martian dust and surface rocks. The iron oxidizes creating rust. We should call it the rusty planet! Many ancient peoples associated the planet with war and conflict because of its blood-red appearance. Indeed, Mars is the Latin name for the ancient Roman god of war.

Mars, like Earth, has clouds in its atmosphere and deposits of ice at its poles. But unlike Earth, Mars has little to no liquid water on its surface. The rustlike color of Mars comes from the large amount of iron in the planet’s soil.
Credit: NASA/JPL/Malin Space Science Systems

Humans have been studying Mars for centuries. Visible from Earth with the unaided eye, Mars has always captivated us! Of all the planets in our solar system, Mars has the surface environment that most closely resembles that of Earth. Mars has weather and seasons and landforms that appear familiar. Salty water may flow just below the planet’s surface. Like Earth, the sun, and the rest of the solar system, Mars is about 4.6 billion years old.

Mars has a special place in popular culture, one that is unique among the planets. This fascination with Mars probably developed because the planet is relatively close to and similar to Earth. Early observations with Earth-based telescopes inspired popular speculation that Mars was home to all kinds of life, even alien civilizations. Many works of science fiction have played upon these ideas, showing humans visiting Mars or malevolent Martians invading Earth.

A Martian landscape includes jagged rocks, sand dunes, and hazy clouds. The image, taken by the United States rover Curiosity, has been adjusted to show the natural color of the planet, as it would appear to an observer on the surface.
Credit: NASA/JPL-Caltech/MSSS

In the 1960’s, the U.S. Mariner spacecraft showed Mars to be a cold, desert planet devoid of visible life. But Mars continues to fascinate people with hints of past surface water and the possibility that microscopic life once existed or still exists there. Experts also view Mars as the next likely target for human space exploration and perhaps even as a stepping stone to exploring the rest of the solar system.

Robotic spacecraft began detailed observation of Mars in the 1960′s. The United States launched to Mars the Mariner 4 probe in 1964 and Mariners 6 and 7 in 1969. The pictures they returned showed a barren surface, covered with craters like those on the moon. There was no sign of liquid water or life. The spacecraft observed few of the planet’s most interesting features because they happened to fly by only heavily cratered regions. But when Mariner 9 went into orbit around Mars in 1971, people’s view of Mars completely changed. Mariner 9 mapped about 80 percent of Mars and made the first discoveries of the planet’s canyons and volcanoes. It also found the first evidence for water, taking photographs of the outflow channels and valley networks.

February 14, 2014

The wildly complicated surface of Ganymede, the largest moon in the solar system, appears in colorful detail in a new map published by the United States Geological Survey. The map is based on images taken by NASA’s Voyager 1 and Voyager 2 spacecraft, which flew by Jupiter and its moons in 1979, and the Galileo probe, which orbited Jupiter from 1995 to 2003. The map is the first global geologic map of Ganymede, Jupiter’s seventh moon, or any other icy moon, for that matter.

Ganymede, also Jupiter’s largest moon, is bigger than the planet Mercury and almost as large as Mars. Ganymede is one of four Jovian moons discovered by the Italian scientist Galileo Galilei in 1610. From observations using Earth-based telescopes and orbiting spacecraft, scientists have long known that Ganymede’s icy surface is made up of almost equal amounts of dark and light material. A thin ocean of salty water may lay about 105 miles (170 kilometers) below the surface. The presence of water makes Ganymede and the other large moons of Jupiter—along with Mars—prime candidates in the search for extraterrestrial life.

The false colors in a new map of Ganymede reveal geologic features created during different times in the moon's history. (USGS Astrogeology Science Center/Wheaton/NASA/JPL-Caltech)

The new false-color map, which was created by a team of scientists headed by Geoffrey Collins of Wheaton College in Massachusetts, provides the first solid evidence for three major geological periods in the moon’s history. During the oldest period, represented in brown, asteroids and comets bombarded the surface, leaving many impact craters. Forces released by the biggest impacts also created large cracks in the moon’s crust. Lighter colors on the map represent two somewhat younger periods. During one of these, changes in the temperature of the moon caused the surface to expand and crack. The new terrain (land) created by these tectonic forces was marked with parallel sets of ridges and valleys. During the third period, geologic activity declined. As the crust settled, new ridges and valleys appeared.

Additional articles in World Book:

• Callisto
• Europa
• Io
• Satellite (Satellites of the gas giants)
• Probing the Planets (a Special Report)
• The Thirty-Year Journey of Voyagers 1 & 2 (a Special Report)

April 18, 2012

The U. S. space shuttle Discovery made its final voyage on Tuesday, April 17, hitching a ride aboard a modified Boeing 747 jumbo jet. Discovery was flown from Kennedy Space Center in Florida to Dulles International Airport in Virginia. There, the shuttle is to become an exhibit at the Smithsonian National Air and Space Museum annex in Chantilly. Discovery replaced the shuttle prototype Enterprise, which will go on exhibit in New York City.

Columbia was the first space shuttle to be launched into space, in 1981. (Courtesy of NASA)

Discovery first flew into space in August 1984, on a mission to deploy three communications satellites. It was the third shuttle in the fleet, following Columbia and Challenger. Discovery carried the Hubble Space Telescope into space in 1990. After the explosions of Challenger in 1986 and Columbia in 2003, Discovery, along with the shuttles Atlantis and Endeavour, carried on the task of ferrying parts and crew members to build the International Space Station (ISS). Construction of the ISS began in 1998, and the shuttles completed the delivery of major station modules by 2011. Discovery flew 39 missions in all, more than any other shuttle. Since its first flight, Discovery has logged more than 148 million miles (238 million kilometers) and spent a cumulative 365 days in space.

The U.S. fleet of space shuttles was instrumental in building the ISS, a space station program in which 15 nations are involved.  (Courtesy of NASA)

President George W. Bush announced plans in 2004 to end the space shuttle program. By that time, engineers had become concerned about the safety of the aging vehicle–the first reusable spacecraft. The government determined that private contractors would take over the shuttle’s responsibilities at the ISS and that NASA would devote its resources to exploring space. The shuttle Endeavour was slated to be put on exhibit in Los Angeles, while Atlantis was to remain at the Kennedy Space Center. Nearly 2,000 people gathered to see Discovery’s final voyage and to mark the end of an amazing era of space exploration.

Additional World Book articles:

• Thirty Years of Discovery (a special report)
• Seeing the Universe in a Different Light (a special report)
• Space exploration 1981 (Back in Time article)
• Space exploration 1984 (Back in Time article)
• Space exploration 1986 (Back in Time article)
• Space exploration 1990 (Back in Time article)
• Space exploration 2000 (Back in Time article)
• Space exploration 2003 (Back in Time article)
• Space exploration 2011 (Back in Time article)

April 13, 2012

North Korea’s much-watched launch of a long-range missile capable of delivering a nuclear weapon failed this morning. The rocket broke up and crashed into the Sea of Japan shortly after being launched from northwest North Korea. According to the government in Pyongyang, the capital, the aim of the launch had been to put a satellite into orbit to mark the 100th anniversary of the birth of Kim Il-sung, founder of North Korea and grandfather of the current leader, Kim Jong-un.

A statue in Pyongyang commemorates Kim Il-sung, the founder of North Korea. (Courtesy of Dermot Tatlow, Panos Pictures)

International affairs experts described the failure as a major loss of face for Kim and his regime. Kim became leader of North Korea at the death of his father, Kim Jong-il, in December 2011.

Additional World Book articles:

• North Korea 2011 (Back in Time article)
• Korea 1994 (Back in Time article)