Mars Facts: Life, Water and Robots on the Red Planet Mars Facts: Life, Water and Robots on the Red Planet By Charles Q. Choi, Space.com Contributor | November 4, 2014 09:00pm ET MORE NASA's Hubble Space Telescope snapped this shot of Mars on Aug. 26, 2003, when the Red Planet was 34.7 million miles from Earth. The picture was taken just 11 hours before Mars made its closest approach to us in 60,000 years. Credit: NASA/ESA Mars is the fourth planet from the sun. Befitting the red planet's bloody color, the Romans named it after their god of war. The Romans copied the ancient Greeks, who also named the planet after their god of war, Ares. Other civilizations also typically gave the planet names based on its color — for example, the Egyptians named it "Her Desher," meaning "the red one," while ancient Chinese astronomers dubbed it "the fire star." Physical characteristics Regolith The bright rust color Mars is known for is due to iron-rich minerals in its regolith — the loose dust and rock covering its surface.

The soil of Earth is a kind of regolith, albeit one loaded with organic content. According to NASA, the iron minerals oxidize, or rust, causing the soil to look red. Geology The cold, thin atmosphere means liquid water currently cannot exist on the Martian surface for any length of time. This means that although this desert planet is just half the diameter of Earth, it has the same amount of dry land. The red planet is home to both the highest mountain and the deepest, longest valley in the solar system. Olympus Mons is roughly 17 miles (27 kilometers) high, about three times as tall as Mount Everest, while the Valles Marineris system of valleys — named after the Mariner 9 probe that discovered it in 1971 — can go as deep as 6 miles (10 km) and runs east-west for roughly 2,500 miles (4,000 km), about one-fifth of the distance around Mars and close to the width of Australia or the distance from Philadelphia to San Diego. Space.com Exclusive T-shirt. Available to Populate Mars.

Buy Now Credit: Space.com Store Mars has the largest volcanoes in the solar system, including Olympus Mons, which is about 370 miles (600 km) in diameter, wide enough to cover the entire state of New Mexico. It is a shield volcano, with slopes that rise gradually like those of Hawaiian volcanoes, and was created by eruptions of lavas that flowed for long distances before solidifying. Mars also has many other kinds of volcanic landforms, from small, steep-sided cones to enormous plains coated in hardened lava. Some minor eruptions might still occur on the planet. Scientists think the Valles Marineris formed mostly by rifting of the crust as it got stretched. Individual canyons within the system are as much as 60 miles (100 km) wide. They merge in the central part of the Valles Marineris in a region as much as 370 miles (600 km) wide. Large channels emerging from the ends of some canyons and layered sediments within suggest the canyons might once have been filled with liquid water.

Channels, valleys, and gullies are found all over Mars, and suggest that liquid water might have flowed across the planet's surface in recent times. Some channels can be 60 miles (100 km) wide and 1,200 miles (2,000 km) long. Water may still lie in cracks and pores in underground rock . Many regions of Mars are flat, low-lying plains. The lowest of the northern plains are among the flattest, smoothest places in the solar system, potentially created by water that once flowed across the Martian surface. The northern hemisphere mostly lies at a lower elevation than the southern hemisphere, suggesting the crust may be thinner in the north than in the south. This difference between the north and south might be due to a very large impact shortly after the birth of Mars. The number of craters on Mars varies dramatically from place to place, depending on how old the surface is. Much of the surface of the southern hemisphere is extremely old, and so has many craters — including the planet's largest, 1,400-mile-wide (2,300 km) Hellas Planitia — while that of northern hemisphere is younger and so has fewer craters.

Some volcanoes have few craters, which suggests they erupted recently, with the resulting lava covering up any old craters. Some craters have unusual-looking deposits of debris around them resembling solidified mudflows, potentially indicating that impactor hit underground water or ice. Polar caps Vast deposits of what appear to be finely layered stacks of water ice and dust extend from the poles to latitudes of about 80 degrees in both hemispheres. These were probably deposited by the atmosphere over long spans of time. On top of much of these layered deposits in both hemispheres are caps of water ice that remain frozen all year round. Additional seasonal caps of frost appear in the wintertime. These are made of solid carbon dioxide, also known as "dry ice," which has condensed from carbon dioxide gas in the atmosphere, and in the deepest part of the winter, this frost can extend from the poles to latitudes as low as 45 degrees, or halfway to the equator. The dry ice layer appears to have a fluffy texture, like freshly fallen snow, according to the report in the Journal of Geophysical Research-Planets.

Mars 12 inch Globe Buy Here Credit: Space.com Store Climate Mars is much colder than Earth, in large part due to its greater distance from the sun. The average temperature is about minus 80 degrees Fahrenheit (minus 60 degrees Celsius), although they can vary from minus 195 F (minus 125 C) near the poles during the winter to as much as 70 F (20 C) at midday near the equator. The carbon-dioxide-rich atmosphere of Mars is also roughly 100 times less dense than Earth's on average, but it is nevertheless thick enough to support weather, clouds and winds. The density of the atmosphere varies seasonally, as winter forces carbon dioxide to freeze out of the Martian air. NASA’s Mars Reconnaissance Orbiter found the first definitive detections of carbon-dioxide snow clouds , making Mars the only body in the solar system known to host the unusual winter weather. The red planet also causes water-ice snow to fall from the clouds. The dust storms of the Mars are the largest in the solar system, capable of blanketing the entire red planet and lasting for months.

One theory as to why dust storms can grow so big on Mars starts with airborne dust particles absorbing sunlight, warming the Martian atmosphere in their vicinity. Warm pockets of air flow toward colder regions, generating winds. Strong winds lift more dust off the ground, which in turn heats the atmosphere, raising more wind and kicking up more dust. Orbital characteristics The axis of Mars, like Earth's, is tilted with relation to the sun. This means that like Earth, the amount of sunlight falling on certain parts of the planet can vary widely during the year, giving Mars seasons. However, the seasons that Mars experiences are more extreme than Earth's because the red planet's elliptical, oval-shaped orbit around the sun is more elongated than that of any of the other major planets. When Mars is closest to the sun, its southern hemisphere is tilted toward the sun, giving it a short, very hot summer, while the northern hemisphere experiences a short, cold winter. When Mars is farthest from the sun, the northern hemisphere is tilted toward the sun, giving it a long, mild summer, while the southern hemisphere experiences a long, cold winter.

Composition & structure Atmospheric composition (by volume): 95.32 percent carbon dioxide, 2.7 percent nitrogen, 1.6 percent argon, 0.13 percent oxygen, 0.08 percent carbon monoxide, minor amounts of water, nitrogen oxide, neon, hydrogen-deuterium-oxygen, krypton, xenon Magnetic field: Mars currently has no global magnetic field, but there are regions of its crust that can be at least 10 times more strongly magnetized than anything measured on Earth, remnants of an ancient global magnetic field. Chemical composition: Mars likely has a solid core composed of iron, nickel, and sulfur. The mantle of Mars is probably similar to Earth's in that it is composed mostly of peridotite, which is made up primarily of silicon, oxygen, iron and magnesium. The crust is probably largely made of the volcanic rock basalt, which is also common in the crusts of the Earth and the moon, although some crustal rocks, especially in the northern hemisphere, may be a form of andesite, a volcanic rock that contains more silica than basalt does.

Internal structure: Scientists think that on average, the Martian core is about 1,800 and 2,400 miles in diameter (3,000 and 4,000 km), its mantle is about 900 to 1,200 miles (5,400 to 7,200 km) wide and its crust is about 30 miles (50 km) thick. Orbit & rotation Average distance from the sun : 141,633,260 miles (227,936,640 km). By comparison: 1.524 times that of Earth Perihelion (closest): 128,400,000 miles (206,600,000 km). By comparison: 1.404 times that of Earth Aphelion (farthest): 154,900,000 miles (249,200,000 km).

By comparison: 1.638 times that of Earth The moons of Mars The two moons of Mars , Phobos and Deimos, were discovered by American astronomer Asaph Hall over the course of a week in 1877. Hall had almost given up his search for a moon of Mars, but his wife, Angelina, urged him on — he discovered Deimos the next night, and Phobos six days after that. He named the moons after the sons of the Greek war god Ares — Phobos means "fear," while Deimos means "rout." Both Phobos and Deimos are apparently made of carbon-rich rock mixed with ice and are covered in dust and loose rocks. They are tiny next to Earth's moon, and are irregularly shaped, since they lack enough gravity to pull themselves into a more circular form. The widest Phobos gets is about 17 miles (27 km), and the widest Deimos gets is roughly nine miles (15 km). Both moons are pockmarked with craters from meteor impacts.

The surface of Phobos also possesses an intricate pattern of grooves, which may be cracks that formed after the impact created the moon's largest crater — a hole about 6 miles (10 km) wide, or nearly half the width of Phobos. They always show the same face to Mars, just as our moon does to Earth. It remains uncertain how Phobos and Deimos were born. They may have been asteroids captured by Mars' gravitational pull, or they may have been formed in orbit around Mars the same time the planet came into existence. Ultraviolet light reflected from Phobos provides strong evidence for its capture origin, according to astronomers at the University of Padova in Italy. Phobos is gradually spiraling toward Mars, drawing about 6 feet (1.8 meters) closer to the red planet each century. Within 50 million years, Phobos will either smash into Mars or break up and form a ring of debris around the planet. Both moons are potential targets for exploration. One NASA plan envisions bombarding Phobos with small, spiky spherical rovers called hedgehogs.

The planet Mars is the fourth planet from the sun and named after the Roman God of War and is also called the Red Planet. See what makes Mars tick with this Space.com infographic looking inside the Red Planet . Credit: Karl Tate, SPACE.com Research & exploration The first person to watch Mars with a telescope was Galileo Galilei , and in the century after him, astronomers discovered its polar ice caps. In the 19th and 20th centuries, researchers believed they saw a network of long, straight canals on Mars, hinting at civilization, although later these often proved to be mistaken interpretations of dark regions they saw. Robot spacecraft began observing Mars in the 1960s, with the United States launching Mariner 4 there in 1964 and Mariners 6 and 7 in 1969. They revealed Mars to be a barren world, without any signs of the life or civilizations people had imagined there. In 1971, Mariner 9 orbited Mars, mapping about 80 percent of the planet and discovering its volcanoes and canyons.

NASA's Viking 1 lander touched down onto the surface of Mars in 1976, the first successful landing onto the Red Planet. It took the first close-up pictures of the Martian surface but found no strong evidence for life . The next two craft to successfully reach Mars were the Mars Pathfinder, a lander, and Mars Global Surveyor , an orbiter, both launched in 1996. A small robot onboard Pathfinder named Sojourner — the first wheeled rover to explore the surface of another planet — ventured over the planet's surface analyzing rocks. In 2001, the United States launched the Mars Odyssey probe, which discovered vast amount of water ice beneath the Martian surface, mostly in the upper three feet (one meter). It remains uncertain whether more water lies underneath, since the probe cannot see water any deeper. In 2003, the closest Mars had passed to Earth in nearly 60,000 years, NASA launched two rovers, nicknamed Spirit and Opportunity , which explored different regions of the Martian surface, and both found signs that water once flowed on the planet's surface.

In 2008, NASA sent another mission, Phoenix, to land in the northern plains of Mars and search for water, Two orbiters — NASA's Mars Reconnaissance Orbiter and ESA's Mars Express — are keeping Mars Odyssey company over the planet. In 2011, NASA's Mars Science Laboratory mission, with its rover named Mars Curiosity , began to investigate Martian rocks to determine the geologic processes that created them and find out more about the present and past habitability of Mars. Among its findings is the first meteorite on the surface of the red planet. In September 2014, India’s Mars Orbiter Mission reached the red planet, making it the fourth nation to successfully enter orbit around Mars. Robots aren’t the only ones looking to buy a ticket to Mars. A workshop group of government, academic, and industry scientists have found that a NASA-led manned mission to Mars should be possible by the 2030s. But NASA isn’t the only one with Martian astronaut hopefuls.. The Mars One colony project is looking to send private citizens on a one-way trip to the red planet. Possibility of life Mars could have once harbored life. Some conjecture that life might still exist there even today.

A number of researchers have even speculated that life on Earth may have seeded Mars, or that life on Mars seeded Earth. The most public scientific claim for life on Mars came in 1996. Geologist David McKay at NASA's Johnson Space Center in Houston and his colleagues focused on rocks blasted off the surface of Mars by cosmic impacts that landed on Earth. Within they found complex organic molecules, grains of a mineral called magnetite that can form within some kinds of bacteria, and tiny structures that resembled fossilized microbes. However, these claims have proven controversial, and there is no consensus as to whether they are signs of life. Mars may have possessed oceans on its surface in the past, providing an environment for life to develop. Although the red planet is a cold desert today, researchers suggest that liquid water may be present underground, providing a potential refuge for any life that might still exist there. The rover Curiosity has found evidence for a lake that could have once supported life on the red planet, after previously establishing that the planet had the key ingredients present for life to evolve. Enthusiasm and excitement on Earth over the possibility of life on the red planet are revealed by the flurry of excitement that greets interesting objects spotted by orbiters and landers.

While the Face on Mars garnered attention for the past four decades after it was first spotted by Viking 1, rovers today show close-ups of objects — such as a weathered Martian rock claimed to be a ‘thigh bone’ and a likely shiny rock that raised furor on the internet as a UFO light . Additional resources Read about and see pictures of more than 40 missions to Mars . Follow the rover Curiosity as it makes its way across the Martian terrain. Learn more about Mars at NASA's Solar System Exploration website. Related: The SF Site Featured Review: Fourth Planet from the Sun A review by Steven H Silver Advertisement Mars orbits the sun at an average distance of 227.9 million kilometers with a period of about 22� earth months. Its bright red, potentially menacing glow early on linked the name of the planet to the gods of blood and war in numerous civilizations. With the publication in 1898 of H.G. Wells's novel, The War of the Worlds, Mars became inextricably linked in the public imagination with aliens and invasion. Even before Wells, the astronomer Giovanni Schiaparelli noted he saw canali on Mars.

Faulty translation of this term into English meant there was a belief that there were artificial waterways on the planet. With the rise of science fiction as a genre in and of itself, Mars became a natural location to posit all sorts of alien life and adventure. Many of the earliest of these used Mars as the setting for wild adventure similar to the way Africa was used. The most notable of these practitioners was Edgar Rice Burroughs who wrote nearly a dozen novels about Mars, or Barsoom, as he called it. In the years since Burroughs published "Under the Moons of Mars" in 1912, our knowledge of the red planet has grown by leaps and bounds. In Fourth Planet from the Sun, Fantasy & Science Fiction editor Gordon van Gelder reprints numerous stories which show the evolution of our knowledge of Mars and its use in fiction over the last half century. If there is one author whose name is more associated with Mars than Edgar Rice Burroughs, it would have to be Ray Bradbury, whose series of fables set on Mars were collected as The Martian Chronicles in 1958. Van Gelder has selected Bradbury's story "The Wilderness" to open this anthology.

Not set on Mars, this is a story about preparations for a journey to the red planet, which makes it clear that Mars, in this case, is a stand-in for the opening of the American West. Other stories included, particularly those of the earlier writers like Leigh Brackett and Roger Zelazny, present a Mars with a rich and diverse culture, modeled more on the pulp fantasies of Burroughs or A. Merritt than on the scientific evidence of conditions of Mars. These escapist tales use Mars as the same sort of lost world as the pulp authors wrote about the strange regions of the Earth. The stories, which date from the late 70s after the Viking landers began to send back details on actual conditions on Mars, demonstrate an understanding and acceptance of the realities of the planet's surface conditions. Even as authors began to base their stories on the aerology of Mars, they refused to completely abandon the idea that Mars could be the home of aliens, as shown by the Martians of Jerry Oltion's "The Great Martian Pyramid Hoax." The stories included in Fourth Planet from the Sun show the possibilities a single venue, however varied, can provide for stories.

While many of the earlier tales could have been set anywhere, since the scientific basis for their setting is non-existent, the latter tales show how science fiction can fully take advantage of the scientific discoveries to create a living breathing world on which to base stories not only of adventure, but also of philosophy. Solar System Planets: Order of the 8 (or 9) Planets Solar System Planets: Order of the 8 (or 9) Planets By Robert Roy Britt | January 22, 2016 12:35pm ET MORE The planets of the solar system as depicted by a NASA computer illustration. Orbits and sizes are not shown to scale. Credit: NASA Ever since the discovery of Pluto in 1930, kids grew up learning about the nine planets of our solar system. That all changed starting in the late 1990s, when astronomers began to argue about whether Pluto was a planet. In a highly controversial decision , the International Astronomical Union ultimately decided in 2006 to call Pluto a “dwarf planet,” reducing the list of “real planets” in our solar system to eight.

However, astronomers are now hunting for another planet in our solar system, a true ninth planet , after evidence of its existence was unveiled on Jan. 20, 2016. The so-called "Planet Nine," as scientists are calling it, is about 10 times the mass of Earth and 5,000 times the mass of Pluto. [ Solar System Pictures: A Photo Tour ] If you insist on including Pluto , then that world would come after Neptune on the list; Pluto is truly way out there, and on a wildly tilted, elliptical orbit (two of the several reasons it got demoted). Interestingly, Pluto used to be the eighth planet, actually. More on that below. Terrestrial planets The inner four worlds are called “ terrestrial planets ,” because, like Earth, their surfaces are all rocky. Pluto, too, has a solid surface (and a very frozen one) but has never been grouped with the four terrestrials.

Jovian planets The four large outer worlds — Jupiter, Saturn, Uranus, and Neptune — are known as the “Jovian planets” (meaning “Jupiter-like”) because they are all huge compared to the terrestrial planets, and because they are gaseous in nature rather than having rocky surfaces (though some or all of them may have solid cores, astronomers say). According to NASA , "two of the outer planets beyond the orbit of Mars — Jupiter and Saturn — are known as gas giants; the more distant Uranus and Neptune are called ice giants." This is because, while the first two are dominated by gas, while the last two have more ice. All four contain mostly hydrogen and helium. Dwarf planets The IAU definition of a full-fledged planet goes like this: A body that circles the sun without being some other object's satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has "cleared its neighborhood" of most other orbiting bodies. Yeah, that’s a mouthful.

The problem for Pluto, besides its small size and offbeat orbit, is that it shares its space with lots of other objects in the Kuiper Belt , beyond Neptune. Still, the demotion of Pluto remains controversial . The IAU planet definition puts other small, round worlds in the dwarf planet category, including the Kuiper Belt objects Eris , Haumea , and Makemake . Also now a dwarf planet is Ceres , a round object in the Asteroid Belt between Mars and Jupiter. Ceres was actually considered a planet when discovered in 1801 and then later deemed to be an asteroid. Some astronomers like to consider Ceres as a 10th planet (not to be confused with Nibiru or Planet X ), but that line of thinking opens up the possibility of there being 13 planets, with more bound to be discovered. The planets Below is a brief overview of the eight primary planets in our solar system , in order from the inner solar system outward: Mercury The closest planet to the sun, Mercury is only a bit larger than Earth's moon.

Its day side is scorched by the sun and can reach 840 degrees Fahrenheit (450 Celsius), but on the night side, temperatures drop to hundreds of degrees below freezing. Mercury has virtually no atmosphere to absorb meteor impacts, so its surface is pockmarked with craters, just like the moon. Over its four-year mission, NASA's MESSENGER spacecraft has revealed views of the planet that have challenged astronomers' expectations. Discovery: Known to the ancients and visible to the naked eye Named for: Messenger of the Roman gods Diameter: 3,031 miles (4,878 km) Orbit: 88 Earth days Venus' southern hemisphere, as seen in the ultraviolet. Credit: ESA Venus The second planet from the sun, Venus is terribly hot, even hotter than Mercury. The atmosphere is toxic. The pressure at the surface would crush and kill you. Scientists describe Venus’ situation as a runaway greenhouse effect. Its size and structure are similar to Earth, Venus' thick, toxic atmosphere traps heat in a runaway "greenhouse effect." Oddly, Venus spins slowly in the opposite direction of most planets. The Greeks believed Venus was two different objects — one in the morning sky and another in the evening.

Because it is often brighter than any other object in the sky — except for the sun and moon — Venus has generated many UFO reports. Discovery: Known to the ancients and visible to the naked eye Named for: Roman goddess of love and beauty Diameter: 7,521 miles (12,104 km) Orbit: 225 Earth days An image of the Earth taken by the Russian weather satellite Elektro-L No.1. Credit: NTsOMZ Earth The third planet from the sun, Earth is a waterworld, with two-thirds of the planet covered by ocean. It’s the only world known to harbor life. Earth’s atmosphere is rich in life-sustaining nitrogen and oxygen. Earth's surface rotates about its axis at 1,532 feet per second (467 meters per second) — slightly more than 1,000 mph (1,600 kph) — at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second).

Diameter: 7,926 miles (12,760 km) Orbit: 365.24 days Day: 23 hours, 56 minutes Related: Mars researchers are focusing both Earth-based and planet orbiting sensors to better understand sources of methane on the red planet. Image Credit: Space Telescope Science Institute Mars The fourth planet from the sun, is a cold, dusty place. The dust, an iron oxide, gives the planet its reddish cast. Mars shares similarities with Earth: It is rocky, has mountains and valleys, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms. It snows on Mars. And Mars harbors water ice. Scientists think it was once wet and warm, though today it’s cold and desert-like. Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time. Scientists think ancient Mars would have had the conditions to support life, and there is hope that signs of past life — possibly even present biology — may exist on the Red Planet.

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of war Diameter: 4,217 miles (6,787 km) Orbit: 687 Earth days Day: Just more than one Earth day (24 hours, 37 minutes) Related: Close-up of Jupiter's Great Red Spot as seen by a Voyager spacecraft. Credit: NASA/JPL-Caltech Jupiter The fifth planet from the sun, Jupiter is huge and is the most massive planet in our solar system. It’s a mostly gaseous world, mostly hydrogen and helium. Its swirling clouds are colorful due to different types of trace gases. A big feature is the Great Red Spot, a giant storm which has raged for hundreds of years. Jupiter has a strong magnetic field, and with dozens of moons, it looks a bit like a miniature solar system.

Discovery: Known to the ancients and visible to the naked eye Named for: Ruler of the Roman gods Diameter: 86,881 miles (139,822 km) Orbit: 11.9 Earth years The shadow of Saturn's moon Mimas dips onto the planet's rings and straddles the Cassini Division in this natural color image taken as Saturn approaches its August 2009 equinox. Credit: NASA/JPL/Space Science Institute Saturn The sixth planet from the sun is known most for its rings . When Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing — a symbol with one large circle and two smaller ones — in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings. The rings are made of ice and rock. Scientists are not yet sure how they formed. The gaseous planet is mostly hydrogen and helium. It has numerous moons .

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of agriculture Diameter: 74,900 miles (120,500 km) Orbit: 29.5 Earth years Day: About 10.5 Earth hours Related: Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which the planet is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory Uranus The seventh planet from the sun, Uranus is an oddball. It’s the only giant planet whose equator is nearly at right angles to its orbit — it basically orbits on its side. Astronomers think the planet collided with some other planet-size object long ago, causing the tilt. The tilt causes extreme seasons that last 20-plus years, and the sun beats down on one pole or the other for 84 Earth-years. Uranus is about the same size as Neptune. Methane in the atmosphere gives Uranus its blue-green tint. It has numerous moons and faint rings.

Discovery: 1781 by William Herschel (was thought previously to be a star) Named for: Personification of heaven in ancient myth Diameter: 31,763 miles (51,120 km) Orbit: 84 Earth years Neptune’s winds travel at more than 1,500 mph, and are the fastest planetary winds in the solar system. Credit: NASA/JPL Neptune The eighth planet from the sun, Neptune is known for strong winds — sometimes faster than the speed of sound. Neptune is far out and cold. The planet is more than 30 times as far from the sun as Earth. It has a rocky core. Neptune was the first planet to be predicted to exist by using math, before it was detected. Irregularities in the orbit of Uranus led French astronomer Alexis Bouvard to suggest some other might be exerting a gravitational tug. German astronomer Johann Galle used calculations to help find Neptune in a telescope. Neptune is about 17 times as massive as Earth. Discovery: 1846 Pluto and its moons orbit the sun near the edge of our solar system.

Learn all about Pluto's weirdly eccentric orbit, four moons and more in this Space.com infographic . Credit: SPACE.com/Karl Tate Pluto (Dwarf Planet) Once the ninth planet from the sun, Pluto is unlike other planets in many respects. It is smaller than Earth's moon. Its orbit carries it inside the orbit of Neptune and then way out beyond that orbit. From 1979 until early 1999, Pluto had actually been the eighth planet from the sun. Then, on Feb. 11, 1999, it crossed Neptune's path and once again became the solar system's most distant planet — until it was demoted to dwarf planet status. Pluto will stay beyond Neptune for 228 years. Pluto’s orbit is tilted to the main plane of the solar system — where the other planets orbit — by 17.1 degrees. It’s a cold, rocky world with only a very ephemeral atmosphere. NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015.

[Related: New Horizons' Pluto Flyby: Latest News, Images and Video ] Discovery: 1930 by Clyde Tombaugh Named for: Roman god of the underworld, Hades Diameter: 1,430 miles (2,301 km) Orbit: 248 Earth years NASA Solar System Exploration: Dwarf Planets Planet Nine Planet Nine orbits the sun at a distance that is 20 times farther out than the orbit of Neptune. (The orbit of Neptune is 2.7 billion miles from the sun at its closest point.) The strange world's orbit is about 600 times farther from the sun than the Earth's orbit is from the star. Scientists have not actually seen Planet Nine directly . Its existence was inferred by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy objects left over from the birth of the sun and planets. Planet Mars - The Solar System on Sea and Sky Mars Reconnaissance Orbiter view of Victoria Crater on Mars (NASA/JPL/University of Arizona) God of War With the Terran system well behind us, we next encounter a beautiful, bright red world.

This is the planet Mars, and it is the fourth planet from the Sun. It was named after the Roman god of war because its color reminded observers of a bloody Roman battlefield. Early astronomers believed they could see faint, dark lines crossing the surface of the planet. Some believed these to be artificially built canals. This gave rise to some of the early speculation of intelligent life on Mars. These lines were later found to be an optical illusion. Later unmanned missions to the planet found no evidence of the so-called canals. Still, there is perhaps no other body in the Solar System that has intrigued us more than Mars. To this very day, it is still one of the most likely candidates for extraterrestrial life. In fact, meteorites recently discovered in Antarctica are believed to have originated from the red planet. These ancient Martian rocks may contain fossils of tiny bacteria. If this turns out to be true, it will be the first evidence that life evolved on other planets besides Earth. Viking lander image the Martian surface showing water ice frost (NASA/JPL) Opportunity rover image of Cape St. Vincent in Victoria Crater (NASA/JPL/Cornell) The Red Planet The bright red color of Mars has earned it the name of red planet.

This unique color is caused by the chemistry of its surface. Mars does have a thin atmosphere, which helps cause iron compounds to oxidize. It is this iron oxide in the rocks and sand that gives the planet it reddish-brown color. It could very appropriately be called the "rusty" planet. We have learned a great deal about Mars in the last few decades. Several unmanned space missions have been sent to explore the red planet. Several Mariner spacecraft orbited the planet in the mid and late 1960's. In 1975, two Viking spacecraft landed on the surface, sending back the first color pictures of this alien world. Recently, the Mars Pathfinder mission visited the planet. A small roving vehicle known as the Sojourner Rover explored the surface sending back the sharpest pictures to date. Scientists continue to be fascinated with Mars because of its similarities to Earth. Some have even suggested that we may be able to colonize the planet in the not too distant future. If the planet does turn out to be completely lifeless, it may be a candidate for a process known as terraforming. This process would involve using various chemical and biological means to make the planet warmer and the atmosphere more hospitable for human life.

Mars Pathfinder image of the Martian surface. The two mountains in the distance are known as the Twin Peaks and are believed to be about 100 feet (30 meters) tall and are about a kilometer (3300 feet) in the distance. (NASA/JPL) Features of Mars Mars is a small, rocky world about half the size of Earth. As small as it is, however, it is a planet of extremes. Mars is the home of the largest known volcano in the Solar System. Olympus Mons is an extinct volcanic crater that rises 15 miles above the Martian surface. That is over twice the height of the tallest mountain on Earth, Mt. Everest. It is a scar so large it can be seen from Earth. Another gigantic feature of the red planet is Valles Marinares. This is the Martian equivalent of the Grand Canyon. This one is much bigger, however. Valles Marinares stretches 3000 miles (4829 km) along the surface of Mars and is 435 miles (700 km) wide at its widest point. If this canyon existed on Earth, it would stretch across the continental United States from coast to coast!

During the Martian winters, the poles of the planet are covered with large sheets of water ice. Several features that resemble riverbeds suggest that there may have been running water on Mars at one time. The thin atmosphere of Mars is composed mainly of carbon dioxide. Winds of up to 300 miles per hour whip up enormous dust storms that constantly erode and reshape the surface of the planet. With an average surface temperature of 60 degrees below zero, it may not seem very hospitable. But with its thin atmosphere and abundance of water, Mars remains the most likely candidate for life anywhere in the Solar System. A future manned mission to the planet is in the works. Only then will we be able to tell if the red planet is really a dead planet. Fantasy and Science Fiction - Fourth Planet from the Sun $17.95 | Trade Paperback | 304 Pages United States and U.S. possessions Canada and elsewhere FOURTH PLANET FROM THE SUN Tales of Mars from The Magazine of Fantasy & Science Fiction Edited by Gordon Van Gelder In the minds of readers and writers of science fiction and fantasy since H. G. Wells's War of the Worlds, Mars has been the hottest of topics.

The fourth planet from the sun is the confirmed obsession of millions of Earthlings, and it is not a fixation that will go away. Perhaps noting the tens of millions of hits on the NASA websites during the recent exploration of Mars, President Bush has declared a manned visit to the red planet the next great goal of the space program. The widespread passionate preoccupation with Mars, combined with the masterful storytelling of the legendary writers in this volume, will seize the imaginations of readers of any generation From the soul-searching poetry of Ray Bradbury's prose to the weirdly paranoid and baroque visions of Philip K. Dick, World Fantasy Award-winning editor Gordon Van Gelder offers some of the greatest science fiction writing on the red planet in Fourth Planet from the Sun. Paper copies, signed by the Editor, are available by either choosing the PayPal button or by using your credit card on our secure server . Table of Contents Mars (Ares), Fourth Planet from the Sun | Wyzant Resources Source Like a badge of blood in the sky, the Red Planet has long stood for the gods of war. Mars' symbol is seen below.

It seems natural that the Greeks named the fourth planet after Ares, since it shines with a red color, resembling blood, which is appropriate for the god of War. The Romans identified their god of War, Mars, with the Greek Ares; now we know the planet as Mars. Mars was the Roman war god; his shield and spear form the planets symbol. He was also a god of agriculture before becoming associated with Ares. Whereas Ares often received a bad name because "war" implied explicit violence, Mars represented securing peace of a nation through war. Therefore, he was more highly revered amongst the Romans than Ares was amongst the Greeks. In the poems of Homer, there are such epithets as these applied to Ares: scourge of mortals, piercer of shields, the bloodstained one. The Romans were well-known as a warlike people; therefore, it is not strange that Mars became their patron god. They built temples for him and honored him by many celebrations during the year.

One of the most famous parts of the city of Rome was called the Field of Mars (Campus Martius), and it was here that the army was reviewed and the spoils of war dedicated after the return of the armies from some successful campaign. The word martial, pertaining to war, came from Mars, the god of War. He was one of the most important of the Roman gods and an entire month of the year was dedicated to him. We still call the third month of the year, March, in his honor.The month was so named because Mars, the patron god of the Romans, was a war-god, and spring campaigns usually began about that time. The Roman year once began with March before it became January. Scientific facts about Mars: It wasnt until 1877 that the planet Mars was found to have any satellites; but, in that year, the American astronomer Asaph Hall discovered two of them. They were very small, being only five or ten miles in diameter, but they were satellites. Hall named them Phobos and Deimos so that in the heavens, as in the myths and in reality, war is accompanied by fear and terror.

Mars characteristic color is primarily due to the high content of oxidized iron in its surface layers. The surface is covered with fine dust that is often whipped up into dust storms by winds blowing at up to 200 mph (325 km/h). Water must have flowed on Mars at some time. The evidence comes from photos of the Valles Marineris taken by the Viking 1 orbiter (launched in 1975 and reaching Mars on July 20, 1976). The Valles Marineris is a system of canyons and cracks of geological origin in the surface of the planet. Some of them show signs of water erosion, with clearly marked tributaries and winding, dried-up riverbeds. No one is certain when the water was there, but it is assumed to have been many millions of years ago. Sign up for free to access more Greek gods resources like . Wyzant Resources features blogs, videos, lessons, and more about Greek gods and over 250 other subjects. Stop struggling and start learning today with thousands of free resources! Mars - Educational facts and history of the planet Mars.

Mars Mars is the fourth planet from the Sun and the seventh largest: Planet Profile mass : 6.4219e23 kg History of Mars Mars (Greek: Ares ) is the god of War. The planet probably got this name due to its red color; Mars is sometimes referred to as the Red Planet. (An interesting side note: the Roman god Mars was a god of agriculture before becoming associated with the Greek Ares; those in favor of colonizing and terraforming Mars may prefer this symbolism.) The name of the month March derives from Mars. Mars has been known since prehistoric times. Of course, it has been extensively studied with ground-based observatories . But even very large telescopes find Mars a difficult target, it's just too small. It is still a favorite of science fiction writers as the most favorable place in the Solar System (other than Earth!) for human habitation. But the famous "canals" "seen" by Lowell and others were, unfortunately, just as imaginary as Barsoomian princesses. The first spacecraft to visit Mars was Mariner 4 in 1965.

Several others followed including Mars 2 , the first spacecraft to land on Mars and the two Viking landers in 1976. Ending a long 20 year hiatus, Mars Pathfinder landed successfully on Mars on 1997 July 4. In 2004 the Mars Expedition Rovers "Spirit" and "Opportunity" landed on Mars sending back geologic data and many pictures; they are still operating after more than three years on Mars. In 2008, Phoenix landed in the northern plains to search for water. Three Mars orbiters ( Mars Reconnaissance Orbiter , Mars Odyssey , and Mars Express ) are also currently in operation. Mars' orbit is significantly elliptical. One result of this is a temperature variation of about 30 C at the subsolar point between aphelion and perihelion. This has a major influence on Mars' climate .

While the average temperature on Mars is about 218 K (-55 C, -67 F), Martian surface temperatures range widely from as little as 140 K (-133 C, -207 F) at the winter pole to almost 300 K (27 C, 80 F) on the day side during summer. Though Mars is much smaller than Earth, its surface area is about the same as the land surface area of Earth. Mars has some of the most highly varied and interesting terrain of any of the terrestrial planets, some of it quite spectacular: Olympus Mons: the largest mountain in the Solar System rising 24 km (78,000 ft.) above the surrounding plain. Its base is more than 500 km in diameter and is rimmed by a cliff 6 km (20,000 ft) high. Tharsis: a huge bulge on the Martian surface that is about 4000 km across and 10 km high.

Valles Marineris: a system of canyons 4000 km long and from 2 to 7 km deep (top of page); Hellas Planitia: an impact crater in the southern hemisphere over 6 km deep and 2000 km in diameter. Much of the Martian surface is very old and cratered, but there are also much younger rift valleys, ridges, hills and plains. (None of this is visible in any detail with a telescope, even the Hubble Space Telescope; all this information comes from the spacecraft that we've sent to Mars.) The southern hemisphere of Mars is predominantly ancient cratered highlands somewhat similar to the Moon . In contrast, most of the northern hemisphere consists of plains which are much younger, lower in elevation and have a much more complex history. An abrupt elevation change of several kilometers seems to occur at the boundary. The reasons for this global dichotomy and abrupt boundary are unknown (some speculate that they are due to a very large impact shortly after Mars' accretion). Mars Global Surveyor has produced a nice 3D map of Mars that clearly shows these features. The interior of Mars is known only by inference from data about the surface and the bulk statistics of the planet.

The most likely scenario is a dense core about 1700 km in radius, a molten rocky mantle somewhat denser than the Earth's and a thin crust. Data from Mars Global Surveyor indicates that Mars' crust is about 80 km thick in the southern hemisphere but only about 35 km thick in the north. Mars' relatively low density compared to the other terrestrial planets indicates that its core probably contains a relatively large fraction of sulfur in addition to iron (iron and iron sulfide). Like Mercury and the Moon, Mars appears to lack active plate tectonics at present; there is no evidence of recent horizontal motion of the surface such as the folded mountains so common on Earth . With no lateral plate motion, hot-spots under the crust stay in a fixed position relative to the surface. This, along with the lower surface gravity, may account for the Tharis bulge and its enormous volcanoes. There is no evidence of current volcanic activity. However, data from Mars Global Surveyor indicates that Mars very likely did have tectonic activity sometime in the past. There is very clear evidence of erosion in many places on Mars including large floods and small river systems.

At some time in the past there was clearly some sort of fluid on the surface. Liquid water is the obvious fluid but other possibilities exist. There may have been large lakes or even oceans; the evidence for which was strenghtened by some very nice images of layered terrain taken by Mars Global Surveyor and the mineralology results from MER Opportunity. Most of these point to wet episodes that occurred only briefly and very long ago; the age of the erosion channels is estimated at about nearly 4 billion years. However, images from Mars Express released in early 2005 show what appears to be a frozen sea that was liquid very recently (maybe 5 million years ago). Confirmation of this interpretation would be a very big deal indeed! (Valles Marineris was NOT created by running water. It was formed by the stretching and cracking of the crust associated with the creation of the Tharsis bulge.) Early in its history, Mars was much more like Earth. As with Earth almost all of its carbon dioxide was used up to form carbonate rocks. But lacking the Earth's plate tectonics , Mars is unable to recycle any of this carbon dioxide back into its atmosphere and so cannot sustain a significant greenhouse effect .

The surface of Mars is therefore much colder than the Earth would be at that distance from the Sun. Mars has a very thin atmosphere composed mostly of the tiny amount of remaining carbon dioxide (95.3%) plus nitrogen (2.7%), argon (1.6%) and traces of oxygen (0.15%) and water (0.03%). The average pressure on the surface of Mars is only about 7 millibars (less than 1% of Earth's), but it varies greatly with altitude from almost 9 millibars in the deepest basins to about 1 millibar at the top of Olympus Mons. But it is thick enough to support very strong winds and vast dust storms that on occasion engulf the entire planet for months. Mars' thin atmosphere produces a greenhouse effect but it is only enough to raise the surface temperature by 5 degrees (K); much less than what we see on Venus and Earth . Early telescopic observations revealed that Mars has permanent ice caps at both poles; they're visible even with a small telescope. We now know that they're composed of water ice and solid carbon dioxide ("dry ice"). The ice caps exhibit a layered structure with alternating layers of ice with varying concentrations of dark dust.

In the northern summer the carbon dioxide completely sublimes , leaving a residual layer of water ice. ESA's Mars Express has shown that a similar layer of water ice exists below the southern cap as well. The mechanism responsible for the layering is unknown but may be due to climatic changes related to long-term changes in the inclination of Mars' equator to the plane of its orbit. There may also be water ice hidden below the surface at lower latitudes. The seasonal changes in the extent of the polar caps changes the global atmospheric pressure by about 25% (as measured at the Viking lander sites). Recent observations with the Hubble Space Telescope have revealed that the conditions during the Viking missions may not have been typical. Mars' atmosphere now seems to be both colder and dryer than measured by the Viking landers ( more details from STScI). The Viking landers performed experiments to determine the existence of life on Mars. The results were somewhat ambiguous but most scientists now believe that they show no evidence for life on Mars (there is still some controversy, however). Optimists point out that only two tiny samples were measured and not from the most favorable locations. More experiments will be done by future missions to Mars.

A small number of meteorites (the SNC meteorites) are believed to have originated on Mars. On 1996 Aug 6, David McKay et al announced what they thought might be evidence of ancient Martian microorganisms in the meteorite ALH84001. Though there is still some controversy, the majority of the scientific community has not accepted this conclusion. If there is or was life on Mars, we still haven't found it. Large, but not global, weak magnetic fields exist in various regions of Mars. This unexpected finding was made by Mars Global Surveyor just days after it entered Mars orbit. They are probably remnants of an earlier global field that has since disappeared. This may have important implications for the structure of Mars' interior and for the past history of its atmosphere and hence for the possibility of ancient life. When it is in the night time sky, Mars is easily visible with the unaided eye. Mars is a difficult but rewarding target for an amateur telescope though only for the three or four months each martian year when it is closest to Earth. Its apparent size and brightness varies greatly according to its relative position to the Earth.

There are several Web sites that show the current position of Mars (and the other planets) in the sky. More detailed and customized charts can be created with a planetarium program . Mars' Satellites Mars has two tiny satellites which orbit very close to the martian surface: Distance Radius Mass Satellite (000 km) (km) (kg) Discoverer Date --------- -------- ------ ------- ---------- ---- Phobos 9 11 1.08e16 Hall 1877 Deimos 23 6 1.80e15 Hall 1877 ("Distance" is measured from the center of Mars). More about Mars, Deimos, and Phobos The Planets of the Solar System USOE Our solar system includes many different planets. In the drawing below, click your mouse on each planet to find its name and a short bit of information about that planet. Keep in mind that the following model of the solar system shows the correct order of the planets, but the sizes of the planets or their distances from each other are not drawn to scale. Notice the order of the planets. Make sure you view information for all the planets. Which planet is closest to the sun?

Which planet is the farthest away from the sun? A good way to remember the order of the planets is to memorize the following sentence. My Very Educated Mother Just Served Us Nine Pizzas. Do you get it? Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto! Now it is time for you to take The Planet Quiz. Click on your choice for the correct answer. Need a hint, or want more information? Click on the photo of the planet to the left of the question. Photos courtesy of NASA . 1. What is the fourth planet away from the sun? 2. What planet is closest to the sun? 3. What planet is the third as you move away from the sun? 4. What planet is the farthest away from the sun? 5. What is the seventh planet as you move away from the sun? 6. What planet is the fifth as you move away from the sun? 7. What planet is the eighth as you move away from the sun? 8. What is the second planet as you move away from the sun? 9. What planet is the sixth as you go away from the sun? Check your answers by highlighting the box at the right! 1.

Mars 2. Mercury 3. Earth 4. Pluto 5. Uranus 6. Jupiter 7. Neptune 8. Venus 9. Saturn Fourth planet - definition of Fourth planet by The Free Dictionary Fourth planet - definition of Fourth planet by The Free Dictionary n. 1. Roman Mythology The god of war. 2. The fourth planet from the sun, having a sidereal period of revolution about the sun of 687 days at a mean distance of 227.9 million kilometers (141.6 million miles) and a mean diameter of approximately 6,794 kilometers (4,222 miles). [Middle English, from Latin Mārs.] Mars (mɑːz) n (Classical Myth & Legend) the Roman god of war, the father of Romulus and Remus. Greek counterpart: Ares Mars (mɑːz) n 1. (Astronomy) Also called: the Red Planet the fourth planet from the sun, having a reddish-orange surface with numerous dark patches and two white polar caps. It has a thin atmosphere, mainly carbon dioxide, and low surface temperatures.

Spacecraft encounters have revealed a history of volcanic activity and running surface water. The planet has two tiny satellites, Phobos and Deimos. Mean distance from sun: 228 million km; period of revolution around sun: 686.98 days; period of axial rotation: 24.6225 hours; diameter and mass: 53.2 and 10.7 per cent that of earth respectively 2. (Alchemy) the alchemical name for iron Mars n. 1. the ancient Roman god of war and agriculture, identified with the Greek god Ares. 2. the planet fourth in order from the sun, having a diameter of 4222 mi. (6794 km), a mean distance from the sun of 141.6 million mi. (227.9 million km), a period of revolution of 686.95 days, and two moons. [< Latin Mārs] Mars (märz) The fourth planet from the sun and the third smallest, with a diameter about half that of Earth. Mars has seasons similar to but much longer than Earth's. See Table at solar system . See Note at planet .

Mars Fourth planet from the Sun – F3 QIC: Chum Bucket The PAX: Chum Bucket PAX of 1 for this morning’s offering of The Punisher. No matter, it went down like this: Mosey to the sideyard for Seal Jacks x 20, Imperial Walkers x 20, Four Count Leg Kicks x 10 each side, Arm Lifts x 20 Jog around front for, along the width of the school gym, High Knees down and back x 2, Butt Kickers down and back x 2, Half sprint down and back x 2. Down and Bear Crawl down, Crab Walk back, Bunny Hop down, and Duck Walk back. Head to the bus loop for Curb Crawl variant. Bear Crawl across for 1 Incline Merkin, flip, and 1 Decline Merkin. Back across for 2 of each and continue until 5 of each completed. Jog around the bus loop around the back of the school for Jenny – 86 Alabama Prom Dates, 75 Merkins, 30 Step Behinds, and 9 Burpees followed by a quick loop around the trees and back.

Another round with 86 Leg Circles (like Box Cutters but circles), 75 Carolina Dry Docks, 30 Four Count Squats, and 9 Burpees. Stroll to the outdoor pavilion for Lindsays – 30 Dips and 10 Two Count Flutter Kicks then 25 and 15 and adjusting by 5 until 10 and 30 are done. Mosey around western perimeter of AO and back to the ShovelFlag. ‘Skin: What is the singular for PAX? Spoiler Alert- Some comparisons with The Martian – the novel and movie (collectively, the “story”). An astronaut is left for dead on Mars when a mission is cut short by a storm. The astronaut awakes to find his mission mates have left him behind and he needs to improvise to survive. OK, the only parallel is YHC was solo this morning.

The Punisher AO, in fact, offers the following advantages over Mars: 1) Oxygen – while scarce on Mars is plentiful at Linwood Holton Elementary; 2) Water – the “mission” this morning wasn’t long enough to require water, but last night’s rain left it all over the ground – again plentiful; and, 3) Proximity – the AO is about 20 minutes from anywhere in Richmond while a manned-mission to Mars takes years to arrive. After some discussions with several F3 brothers, we’ll keep The Punisher at 5:30 AM on Monday mornings with the expectation that the workout numbers will grow again in the Fall once vacations end.

Question: Which is the fourth planet from the Sun?
Answer: Mars