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Mars is the next planet out from the Sun after Earth, and the outermost of the four rocky planets. It is a dry, cold world with a landscape marked by deep canyons and towering volcanoes. Mars is about half the size of Earth, and like Earth it has polar ice caps and seasons, and it spins around in a little over 24 hours. |
Kasei Vallis |
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| Features such as Kasei Vallis bear witness to the presence of large amounts of fast-flowing water 3-4 billion years ago. This outflow channel, a few hundred miles wide, was probably formed by catastrophic flooding and glacial activity. |
Olympus Mons |
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| This is an overhead view of the summit of Olympus Mons. At 15 miles high, it is the biggest volcano in the solar system. |
Red Planet |
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| Much of Mars is rocky, sandy, and dusty, and large areas of its terrain resemble a rock-strewn desert. It is often referred to as the Red Planet, with its coloring coming from iron oxide (rust) in the rocks and soil. |
The God of War |
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In ancient Rome, Mars was initially a god of fertility and agriculture, but later he also became the God of War. As such, he was widely worshipped, for battles and war are important components of life as the city-state expanded its empire. It is likely that the fourth planet from the Sun became associated with this war like god because of its red color - the color of blood. Military commanders took part in ceremonies to Mars before setting out for work, and soldiers believe that the god, together with a female companion, appeared on the battlefields. The importance of the God was also boosted by the legend that Mars, the God of War, was the father of the twins Romulus and Remus, who were the mythical founders of Rome. |
The Canals of Mars |
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Mars is normally so far away that even through a large telescope it appears just a tiny featureless red.. Fortunately, every two years or so, there is an opportunity to observe the planet close up when it is relatively close to Earth at opposition. This occurs when Earth, in its yearly circuit around the Sun, catches up with the slower-moving Mars, placing it exactly on the opposite side of Earth to the Sun. As Mars has a somewhat elongated path around the Sun, on some of those occasions it is closer to Earth and brighter, and hence the opposition is regarded as more favorable. A most favourable opposition took place in August 2003, while the next similar one will be in July 2018. A number of astronomers observed Mars during the favorable opposition of 1877. Among them was the Italian astronomer Giovanni Schiaparelli, who thought he saw dark lines criss-crossing the planet. In publications, Schiaparelli described the lines as "canali," which in English means "channels." Of course the inevitable happened and "canali" was mistranslated as "canals," a word meaning waterway, but with the implication that they are artificial and constructed by intelligent creatures. |
Atmosphere |
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The atmosphere of Mars is so thin that average atmospheric pressure on the surface is less than one-hundredth of that on Earth. The composition is unsuitable for humans as it is mainly carbon dioxide with small amounts of oxygen and argon, as well as traces of oxygen and water vapor. Despite the thinness of the atmosphere, strong winds can blow that, on occasion, and cause major dust storms covering the whole planet. Mars is also much cooler than Earth, since its orbit around the Sun is 50% further away, and hence receives less than half of the amount of solar energy. However, the planet's path around the Sun is somewhat elongated, so there are large variations in the solar energy it receives. Surface temperatures can vary from -207 degrees fahrenheit at the poles during the winter, to a pleasant 81 degrees fahrenheit on a summer's day. During oppositions, North and South polar caps are easily visible on the disk of the planet through a telescope. These visible polar caps are largely solid carbon dioxide or dry ice. When it is summer at one of the poles, the dry ice turns into gas and shoots into the atmosphere in jets with speeds of around 100 mph, leaving behind a layer of water ice. In winter, the process reverses and a layer of solid carbon dioxide is again deposited to cover the pole. |
The Surface |
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| Mars has a surface that is generally desert-like with everything covered by red dust. Due to past impacts, numerous craters of various sizes dot the surface. Surprisingly, there are major differences between the southern and northern hemispheres. The southern hemisphere is much more heavily cratered than the northern and is higher by about 3 miles. Scientists consider that the heavily cratered Southern Highlands are very ancient. They do not fully understand the differences between the two hemispheres, but most consider that, in the north, younger material has buried an ancient surface similar to that in the south. |
The Largest Crater |
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Hellas Planitia is a giant impact crater in the southern hemisphere of Mars. It is over 1,250 miles across and is 6 miles deep as measured from its rim. Scientists consider that it was created by an impact during the early days of the Solar System when huge numbers of large rocks were moving around the Solar System and bumping into Earth, the Moon, and other bodies. Much material was thrown up by the impact and piled up to form a very wide elevated rim around the crater. The giant crater is large enough to be seen from Earth during opposition's. It was Giovanni Schiaparelli of canals fame who named it Hellas - meaning Greece - on his 1877 map of Mars. Through a telescope, observers can easily mistake Hellas Planitia for the South Pole of the planet, as it appears white in contrast with its surroundings and can be fairly bright. |
Moons of Mars |
Phobos
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| Phobos is the larger and innermost of the two, the other being Deimos. Both moons were discovered in 1877 by American astronomer Asaph Hall. Phobos is a small, irregularly shaped object with a mean radius of 11 km (7 miles), and is seven times more massive than Deimos, Mars's outer moon. Phobos is named after the Greek god Phobos, a son of Ares (Mars) and Aphrodite (Venus) which was the personification of Horror. |
Deimos
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| Deimos is the smaller and outer of the two natural satellites of the planet Mars with a mean radius of 6.2 km (3.9 mi), the other being Phobos. Deimos takes 30.3 hours to orbit Mars. The name Deimos is pronounced /'da?m?s/ DY-m?s, or sometimes /'di?m?s/ DEE-m?s or like the Greek Δε?μος. In Greek mythology, Deimos was the twin brother of Phobos and personified terror. |
Mars Statistics |
| Discovered | Known from antiquity |
| Average distance from the Sun | 142 million miles (228 million km) 1.52 AU |
| Equatorial diameter | 4,222 miles (6,794 km) |
| Axial tilt | 25.19° |
| Axial rotation period (sidereal) | 24.62 hours (prograde) |
| Orbital period (in Earth days) | 686.93 days |
| Mass (Earth=1) | 0.11 |
| Volume (Earth=1) | 0.15 |
| Surface gravity (Earth=1) | 0.38 |
| Average density (water=1) | 3.93 |
| Surface atmospheric pressure (Earth=1) | 0.007 |
| Escape velocity | 3 miles/s (5 km/s) |
| Orbital eccentricity | 0.09 |
| Highest suface temperature | 80°F (27°C) |
| Lowest surface temperature | -207°F (-133°C) |
| Sunlight strength | 36-52% of Earth's |
| Albedo (reflectivity) | 15% |
| Number of satellites | 2 |
Mars Timeline |
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1609 Galileo Galilei (1564 - 1643), often called the "father of modern astronomy," makes the first telescopic observations of Mars and goes on to make notes of the different phases of the planet. He uses telescopes he makes himself, with approximately 32x magnification. |
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1619 Kepler publishes his 3rd Law of Planetary Motion, in which he makes notes of Mars's movement through the universe. |
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1659 Huygens estimates the size of Mars and arrives at an approximate 24-hour rotational period. |
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1666 Gian Cassini, the famous italian-born astronomer, observes the polar cap on Mars. He also calculates and measures the length of the Martian day to be 24 hours and 40 minutes. |
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1671 Gian Cassini measures the distance from Earth to Mars. |
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1672 Huygens observes a white spot on the South Pole of Mars. |
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1698 Huygens publishes Cosmotheoros, a book about whether or not there is life on Mars. |
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1704 Giacomo Filippo Maraldi (the nephew of the famous astronomer Gian Cassini) observes white spots on the North and South poles of Mars. In 1719, he suggests that the white spots could be ice caps on the polar regions. |
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1781 Sir William Herschel discovers that the inclination of Mars's axis of rotation is approximately 24°. |
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1784 Sir William Herschel observes the seasonal changes on the polar caps of Mars and raises the possibility that they might be composed of snow and ice - just as Maraldi had done some 80 years earlier. |
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1894 Lowell Observatory is established in the USA for the sole purpose of studying Mars. |
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1905 C.O. Lampland of the Lowell Observatory takes a photograph of Mars that shows 38 canals. |
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1953 On the initiative of the Lowell Observatory, an international Mars committee is organized to coordinate continuous observation of Mars during the favorable opposition of 1954. |
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1962 NASA builds a series of spacecraft to explore the inner Solar System, including Mars, Venus, and Mercury. As a result, Mariner 4 sends first close-up pictures of Mars during its flyby. |
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1971 Mariner 9 becomes the first satellite orbiting Mars for almost a year. |
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1976 Viking 1 and 2 land on Mars after first imaging the surface to enable landing spots to be selected. These are the first landings of spacecraft on another planet. They both return images of the entire planet in what was then high resolution. |
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1997 Mars Global Surveyor begins orbiting Mars. Mars Pathfinder also lands on Mars and begins to send back excellent data. |
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2004 NASA successfully lands Mars twin rovers, Spirit and Opportunity, on Mars, watched by millions on live television feeds back on Earth. The rovers were seen to roll off their landing gear and begin exploration. |
Where to? |
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