Space

Since the seventeenth century, observers have seen a huge, oval red spot south of Jupiter’s equator. The Great Red Spot has a greater surface area than Earth: 8,400 miles (13,440 km) wide by 24,000 miles (38,400 km) long. Scientists have determined that the spot is a huge atmospheric storm. It appears as a hollow, or […]

The moons all revolve around their host planet, Jupiter, but their orbits are different in distance, speed, and inclination of orbital plane. This all makes for quite a bit of activity. Jupiter’s moons act something like a microcosm, or a miniature version of the solar system, and astronomers have learned a lot about the whole […]

One of the best known features of the planet Jupiter is the Great Red Spot. The Great Red Spot is a permanent anticyclonic storm, and is significantly larger than the Earth. The spot on Jupiter usually can be found 22° south of the equator, in or near the South Equatorial Belt. It rotates counterclockwise, with […]

Jupiter’s sixteen known moons travel in three distinct groups. The first, including the four Galilean moons, ranges from 77,000 miles (124,000 km) to over 600,000 miles (960,000 km). The next group orbits from 6.6 million miles (10.56 million km) to almost 7.2 million miles (11.52 million km) away. The third family of satellites is almost […]

If Jupiter had just eighty times more mass, it could be a star. However, if it were a star, Earth would not exist. Jupiter and the Sun would be a binary star system and the solar system would be completely different. The largest planet in the solar system, Jupiter measures near 88,700 miles (141,920 km) […]

Although Jupiter is a great distance from the Sun, it is a relatively hot planet. Scientists have discovered that almost twice as much heat radiates from the planet’s rocky core than is received from the Sun. The core’s exact temperature is unknown, but it is probably around 30,000°K (53,500°F/30,000°C). Jupiter continues, from the time of […]

Jupiter’s primary gases, hydrogen and helium, are colorless. Trace chemicals within the planet’s gas layers, such as methane, ammonia, and phosphine, are responsible for the colors of the belts and zones. The colors range from cream and yellow through pink, orange, and brown to brick red. Brighter areas suggest hotter temperatures, and darker areas, cooler […]

The Great Red Spot on Jupiter is a persistent anticyclonic storm that is about 24–40,000 km × 12–14,000 km, and is large enough to contain two or three planets the size of Earth. We don’t know whether or not the Great Red Spot will disappear for good one day. Storms on Earth sooner or later […]

Jupiter has sixteen known satellites, but astronomers believe there could be more. The discovery of the four largest, Ganymede, Callisto, Io, and Europa, is credited to Galileo, who recorded them in 1610. The average diameter of the Galilean moons measures 2,540 miles (4,230 km), whereas the average diameter of the other Jovian moons is a […]

Size and composition are the two major characteristics shared by Jupiter, Saturn, Uranus, and Neptune. The smallest outer planet, with the exception of Pluto, which is in a category by itself, is Neptune, and Neptune is almost four times larger than Earth. The outer planets have small cores and huge gaseous outer surfaces. When the […]

Jupiter is a big planet. The planet Jupiter is the largest planet in our Solar System, with a diameter of 142,984 km at its equator. It’s larger than all the other planets and their moons combined, almost big enough to be a star. 1321 earths could fit inside Jupiter. Most of its bulk comes from […]

The planet Jupiter’s rotation is the fastest of all the Solar System’s planets. Jupiter does not rotate as a solid body does, all at the same speed, because it is made out of hydrogen and helium. Around the equator, the gas layer of Jupiter has a rotation period of 5 hours, 50 minutes, and 30 […]

According to current speculation, Jupiter probably has a small, solid core of silica. Above that lies a shell of a different form of liquid hydrogen. Jupiter’s core is surrounded by dense metallic hydrogen, which extends outward to about 78 percent of the radius of the planet. Droplets of helium and neon precipitate downward through this […]

Some eighteen zones and belts can be identified by their different colors, brightness, spots, and rotation periods. Zones are dark bands; belts are bright bands. The main two are the North Equatorial Belt, at approximately 7° to 20° latitude, and the South Equatorial Belt, at approximately –7° to –21° latitude. Both change in width, with […]

The planet Mars seems to have a rocky crust approximately 30 miles (50 km) deep. Its mantle is rich in the element silica, like Earth, but it is solid, unlike Earth’s partially molten mantle. There is no magnetic field on Mars, so presumably its core is solid. It is likely to be solid iron. While […]

The surface of Mars is covered in a fine dust that is rich in iron oxide, also known as rust. There are massive winds on the planet that create dust storms, and so a red-pink smog always hangs over it. Consequently, Mars’s general appearance is red, but powerful telescopes reveal that the surface is multicolored. […]

Experiments on Earth have concluded that certain cells can survive a simulated Martian environment. In 1996, a meteorite that originated on Mars was discovered. The announcement that this rock contained possible evidence of life on Mars or evidence that life once existed on Mars, has sped up plans to send missions back there. Remember, however, […]

One of the most intriguing, and fanciful, photographs taken of Mars by Voyager 1 showed what appeared to be a mask-like face of a human being buried just under the surface. Imagine the uproar in the scientific and science fiction communities. The “face on Mars” turned out to be a purely natural surface formation that, […]

The planets that orbit the Sun beyond the asteroid belt in our solar system are known as the outer planets. Besides their location, they share many other similarities, except for Pluto, which is a highly unusual planet. Jupiter, Saturn, Uranus, and Neptune are all much larger than Earth and are made mostly of gas. This […]

The atmosphere on Mars is relatively weak. It is so thin that damaging ultraviolet solar radiation makes its way unimpeded to the planet’s surface. Carbon dioxide makes up 95 percent of the atmosphere, followed by nitrogen (2.7 percent) and argon (1.6 percent). Oxygen, water vapor, neon, krypton, xenon, and ozone comprise less than 1 percent […]

Mons Olympus, the tallest known volcano, and mountain, in the solar system, is one of many large volcanoes on Mars. Mons Olympus is about 27 km tall, and can be found in the vast upland region Tharsis, which contains several other large volcanoes. Mons Olympus is Latin for “Mount Olympus”, and is believed to have […]

Mars is a pretty cold planet. The average air temperature is –22°F (-30°C) in the day and –148°F (-100°C) at night. Surface temperatures on Mars vary from lows of about -87 °C during the polar winters to highs of up to -5 °C during the summers. The highest temperatures occur during the summer at the […]

The northern ice cap is permanently frozen water covered by frozen carbon dioxide (dry ice), which solidifies from the atmosphere at cold temperatures. During summer in the north, the ice cap shrinks, as some of the carbon dioxide reverts to gas in the atmosphere. In the winter, it grows much larger again. The ice cap […]

Evidence of water has fed scientific debates on the possibility of life on Mars for centuries. A well-known twentieth-century astronomer, Percival Lowell, spent his career mapping what he believed were irrigation canals built by Martians. His findings have been proven false, but there are dry channels on Mars that look like they were created by […]

More craters are found in the southern hemisphere on Mars. This makes astronomers think that the surface there is older than in the northern hemisphere. Something happened in the north, perhaps volcanic activity or water erosion, to cause craters to disappear. There is further evidence supporting the astronomers’ theory: the surface of the northern hemisphere […]

Mars has the deepest canyon in the solar system, the Vallis Marinaris, measuring 4.2 miles (6.7 km) deep, 300 miles (500 km) wide, and 2,800 miles (4,500 km) long. The nearby canyons average about 1.8 miles (3 km) deep. The deepest crater on Mars is the Hellas Planitia, some 3.6 miles (6 km) deep. Mars’s […]

Mars is home to the tallest and largest known volcano in the solar system: Mons Olympus. This extinct shield volcano has a base of about 420 miles (700 km) and reaches 15 miles (25 km) into the atmosphere. Its caldera (large opening) measures 53 miles (85 km) in diameter. By comparison, Mt. Everest, the tallest […]

How Do We Know So Much About the Planet Venus and How Much of Venus Has been Mapped By Astronomers? A number of unmanned spacecraft have flown by and even landed on the planet to take photographs. The views aren’t terribly appealing, dry broken rocks, small mounds, flat terrain, but they are informative. The probes […]

Mars, the closest superior planet to Earth, and the fourth planet from the Sun, frequently looks red, so it is sometimes called the red planet. We know a lot about Mars because it comes closer to Earth than any other planet in favorable opposition, in the best position for viewing, and because we have sent […]

No planet has a truly circular orbit around the Sun. Mars’s orbit is particularly elongated, which affects the planet’s seasons. Mars takes 788 Earth days to orbit the Sun. At its farthest (aphelion), it is about 155 million miles (250 million km) from the Sun. At its closest (perihelion), Mars is some 130 million miles […]

Summer in the southern hemisphere causes the most weather activity on Mars. The temperature increase shrinks the southern polar ice cap, at the same time, the northern ice cap, experiencing winter, grows larger, which increases the air pressure. Increased air pressure causes severe winds to blow toward the equator. The winds can reach up to […]

Mars’s axis is tilted 25.2°, compared to Earth’s 23.5°, and Mars is tilted in the same direction. This causes the planet Mars to have summer and winter, like Earth. Martian seasons are longer because it takes Mars longer to orbit the Sun. The seasonal temperatures on Mars stay much colder than on Earth because Mars […]

During winter in the southern hemisphere on Mars, the polar ice cap grows to cover almost one-quarter of the planet. At the same time, during summer in the northern hemisphere, the northern ice cap is shrinking. Temperatures on Mars can reach as low as –190°F (-123°C). Sometimes a frost consisting of water and dust covers […]

If all those planetesimals and asteroids were flying around some 4 billion years ago, colliding, accreting, and taking chunks out of planets, why don’t we see much evidence of them on Venus? Asteroids probably did hit Venus as much as any other planet; they just didn’t leave behind much visible evidence. Venus’s atmosphere would have […]

Because both Venus and Mercury are inferior planets, lying between Earth and the Sun, they exhibit phases, just like the Moon does, as they orbit the Sun. Venus is full during superior conjunction, on the other side of the Sun from Earth, and new during inferior conjunction, between the Sun and Earth. As it cycles […]

Venus transits the Sun, but not with every revolution. The reason for this is that its orbital plane is at a 3 percent incline to the ecliptic, the Sun’s apparent path around Earth. Only when Venus crosses the ecliptic at the time of its inferior conjunction will it transit the Sun. It usually passes above […]

The planet Venus makes one rotation on its axis in 243 Earth days. Its solar day, the time it takes the Sun to reappear in the same place in the sky, is 118 Earth days. On Earth, the two are almost identical, 24 hours, so the Sun rises at approximately the same place every morning. […]

Why Does the Planet Venus Shine So Brightly In the Sky and How Much Sunlight Does Venus Reflect? Oddly enough, Venus is so brilliant because it is covered in clouds. These clouds are about 10 miles (16.5 km) thick and begin about 50 miles (83 km) above the ground. From the surface of a planet, […]

The clouds on Venus move, but not like clouds on Earth. Venus’s atmosphere is very thick and heavy. There are no major temperature or air pressure changes to cause air currents, as on Earth, but Venus’s atmosphere rotates around the planet at a fairly steady rate of 225 miles (360 km) per hour. The cloud […]

On Earth, clouds are created through water evaporation and condensation. The clouds are water-based. Venus’s clouds are made by a process called photochemistry, whereby the Sun’s ultraviolet rays react with chemicals in Venus’s atmosphere. The clouds around Venus have an acid base, sulfur dioxide. On Earth, sulfur dioxide is released during volcanic activity. It’s what […]

The Planet Venus is very hot indeed. The surface temperature averages almost 900°F (480°C) around the whole planet. This extreme heat results from the greenhouse effect, which occurs when infrared, or heat-producing rays from the Sun enter an atmosphere and cannot get back out. Carbon dioxide, which makes up 96.5 percent of Venus’s atmosphere, lets […]

The first few things you would notice if you could stand on Venus would probably be the heat, the relatively constant calm weather, and the orange-colored rocks and dry dirt at your feet. In general, it might feel like you were in one of the Great Plains states in the middle of a billion-year-long drought. […]

The transit of Venus was first observed in 1032 by the Persian astronomer Avicenna, but Venus has long been known to ancient civilizations as the “morning star” or “evening star”. He concluded that Venus is closer to the Earth than the Sun. Venus, the second planet from the Sun, is sometimes called the twin of […]

All of the other planets besides Venus, and Pluto, rotate on their axes from west to east, causing the Sun to rise in the east and set in the west. Venus’s rotation is called retrograde, moving from east to west. All eight planets in our solar system orbit the sun in the direction that the […]

The planet Venus has an extremely dense atmosphere. The atmosphere on Venus, the second planet from the Sun, consists primarily of carbon dioxide (96.5 precent). Nitrogen makes up 3.5 percent of the atmosphere. Traces of gases such as sulfur dioxide, carbon monoxide, hydrochloric acid, and oxygen (0.00003 percent) have also been detected. The atmospheric mass […]

The Romans who derived their religious pantheon from the Greek tradition, named the planet Venus after their goddess of love. On Venus, all topographical features except one are named for women, Venus being a goddess of womanhood. For instance, the main craters include Anna Pavlova (1881-1931), the prima ballerina of her lifetime; Sacajewea (c. 1789-1812), […]

Like Mercury, Venus is relatively close to the Sun. It is often called the evening or morning star because it is so bright at sunset and sunrise. Venus is the brightest planet in the sky, even brighter than the stars; therefore, it is a pretty easy object to find in the night sky. As a […]

The two major results of Venus’s atmosphere are the amount of pressure it exerts on the planet’s surface and the heat it traps. Carbon dioxide is a heavier gas than nitrogen. Because the atmosphere is more than 96 percent carbon dioxide, the pressure is ninety times greater on Venus than on Earth. Without state-of-the-art, space-age […]

Mercury is thought to be the densest of all the planets, which makes sense when you consider the theory that during the early phases of the solar system’s formation, the lightest materials were sent farthest into space. For a planet so small to be so dense, it may be mostly solid metal. Scientists believe that […]

We look at the way land, terra in Latin, was formed on Earth to understand how the surfaces of other terrestrial planets evolved. Volcanoes created most of Earth’s terrain. Molten material from Earth’s mantle bubbled up 4 billion years ago to form the first continents. On Mercury, land ridges provide evidence of extreme volcanic activity […]

An inferior planet, closer to the Sun, will appear in phases, like the Moon. As Mercury orbits, we generally only see it as a waxing or waning crescent. At a superior conjunction, lined up Earth-Sun-planet, Mercury is full, but it usually can’t be seen from Earth because it’s behind the Sun. We also cannot see […]

A Mercurial year, or the time it takes for Mercury to revolve around the Sun once, is the equivalent of about 88 Earth days (2,112 hours). A Mercurial solar day, the time it takes for the Sun to go from high noon to high noon as seen from Mercury’s surface, takes 176 Earth days (4,224 […]

The planet Mercury is too small for its gravity to retain any significant atmosphere over an extended period of time. However, Mercury does have a “tenuous surface-bounded exosphere” containing hydrogen, helium, oxygen, potassium, and other elements. The hydrogen and helium that make up Mercury’s very thin atmosphere don’t actually originate on the planet. The gases […]

Just looking at the planet Mercury doesn’t give astronomers very much information. Fortunately, electromagnetic waves, mostly radio waves, from Mercury are picked up around the world. They have helped establish the topography and composition of Mercury. Also, twice in 1974 and once in 1975, the spacecraft Mariner flew by Mercury and photographed as much of […]

The earliest known recorded observations of Mercury are from the Mul.Apin tablets around the 14th century BC. The ancient Greeks called the planet Στίλβων (Stilbon), which means “the gleaming”. The Romans named the planet Mercury after the swift-footed Roman messenger god, Mercury, or Mercurius in Latin. Mercury is the smallest planet in the solar system […]

The planet Mercury seems to have been hit by a lot of asteroids. Just under 50 percent of Mercury’s surface has been photographed by spacecraft. The photos show an average of one hundred to one thousand 6-mile (10-km) craters per each 600,000 square miles, or 1 million square kilometers. The appearance of so many craters, […]

Mercury orbits the Sun once every 88 days at a speed of 29.8 miles (48 km) per second. Its aphelion (farthest point from the Sun) is at a distance of 43 million miles (69 million km). Mercury’s perihelion (closest distance from the Sun) is 30 million miles (46 million km). Because this orbit is not […]

Consider where Mercury is located, an average of 36 million miles from the Sun. Since Mercury never travels far from the Sun, it is not visible at night. But looking for it during the day is dangerous, because of its proximity to the Sun. If you scan the sky, with binoculars, a telescope, or your […]

The largest crater photographed so far has been named Beethoven, after the famous composer Ludwig van Beethoven. Mercury’s topographic features are named for famous people, such as Shakespeare and Michelangelo; exploration ships, including the Santa Maria; radar installations, such as the Russian (Soviet) Vostok; and other gods, such as the Scandinavian king of gods, Odin. […]

What Is the Most Obvious Physical Feature On the Planet Mercury and How Many Impact Craters Does Mercury Have? The largest topographic feature seen on Mercury is the Carolis Basin, a depression as wide as Texas about 800 miles (1,280 km in diameter). It is bordered on one side by tall mountains, called scarps, which […]