ភពអង្គារ

ភពអង្គារ
Mars  

Mars as seen by the Hubble Space Telescope
Designations
Pronunciation	/ˈmɑrz/
Adjective	Martian
លក្ខណៈទូទៅនៃគន្លងគោចរ
Epoch J2000
Aphelion	249,209,300 km 1.665 861 AU
Perihelion	206,669,000 km 1.381 497 AU
Semi-major axis	227,939,100 km 1.523 679 AU
Eccentricity	0.093 315
Orbital period	686.971 day 1.8808 Julian years 668.5991 sols
Synodic period	779.96 day 2.135 Julian years
Average orbital speed	24.077 km/s
Inclination	1.850° to ecliptic 5.65° to Sun's equator 1.67° to invariable plane
Longitude of ascending node	49.562°
Argument of perihelion	286.537°
Satellites	2
លក្ខណៈទូទៅនៃសណ្ឋានខាងក្រៅ
Equatorial radius	3,396.2 ± 0.1 km 0.533 Earths
Polar radius	3,376.2 ± 0.1 km 0.531 Earths
Flattening	0.005 89 ± 0.000 15
ផ្ទៃដី	144,798,500 km² 0.284 Earths
មាឌ	1.6318×10១១ km³ 0.151 Earths
ម៉ាស់	6.4185×10២៣ kg 0.107 Earths
Mean density	3.934 g/cm³
Equatorial surface gravity	3.69 m/s² 0.376 g
Escape velocity	5.027 km/s
Sidereal rotation period	1.025 957 day 24.622 96 h
Equatorial rotation velocity	868.22 km/h (241.17 m/s)
Axial tilt	25.19°
North pole right ascension	21 h 10 min 44 s 317.681 43°
North pole declination	52.886 50°
Albedo	0.15 (geometric) or 0.25 (bond)
សីតុណ្ហភាពផ្ទៃខាងក្រៅ    Kelvin    Celsius	min mean max 186 K 227 K 268 K −87 °C −46 °C −5 °C
Apparent magnitude	+1.8 to −2.91
Angular diameter	3.5—25.1"
បរិយាកាស
សម្ពាធផ្ទៃខាងក្រៅ	0.6–1.0 kPa
Composition	95.72% Carbon dioxide 2.7% Nitrogen 1.6% Argon 0.2% Oxygen 0.07% Carbon monoxide 0.03% Water vapor 0.01% Nitric oxide 2.5 ppm Neon 300 ppb Krypton 130 ppb Formaldehyde 80 ppb Xenon 30 ppb Ozone 10 ppb Methane

Mars is the fourth planet from the Sun in the Solar System. Mars is named after the mythological Roman god of war because it is a red planet, which signifies the colour of blood.

Appearance

Surface with rocks everywhere photographed by Mars Pathfinder

Mars has two very small moons, called Phobos and Deimos. The planet Mars is made of rock. The ground there is red because of iron oxide (rust) in the rocks and dust. The planet has a small carbon dioxide atmosphere. The temperatures on Mars are colder than on Earth, because it is farther away from the Sun. There is some ice at the north and south poles of Mars, and also frozen carbon dioxide. Mars does not have any water on the surface now, except at the poles, but most scientists think it used to have water.

The average thickness of the planet's crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi). Earth's crust, on average 40 km (25 mi), is three times smaller than Mars’ crust based on the sizes of the two planets if they are made equal.

History of Mars

Mars has been known since the old times. The Greeks named this planet Ares, after their god of war. The Romans named the planet Mars, after their God.

Some of the first attempts at making a map of Mars were done by Giovanni Schiaparelli. What he saw through his telescope confused him. He saw what he called canali, which he thought were ditches dug for water to pass through. Because of this, people thought that there were other animals and life on Mars, possibly even aliens. Today, we know there cannot be any such aliens. This is because the crafts sent to Mars have found no trace of alien life, and what could have been bacteria were formed at temperatures too high for life to exist. What Giovanni actually saw were the scratches on his telescope lense. This may sound completely absurd but this is really what happened; he spent his whole life studying the marks on his telescope thinking they were alien made water streams.

Life, climate and atmosphere of Mars

Life on Mars?

Because Mars is the one of the closest planets to Earth in the Solar System, some people have wondered if there is any kind of life on Mars. Recently, scientists found an old meteorite that had landed near the Earth's South Pole and decided it had come from Mars. In the meteorite they found some very tiny little shapes in the rock which they think might be fossils made by living things. However, they were not sure if it was life or just the natural patterns of the rock. If it were the fossils of a living thing, it was probably some simple plant, and one hundred of them could fit across the width of a single hair.

It is also possible that there are also pieces of the earth on Mars. If a giant meteorite hit the Earth, the force would be strong enough to send pieces of the earth up to space. If a piece of Earth left the atmosphere, it would take along with it lots of cells and bacteria, which are living things.

Martian Rotation

Mars rotates in 24 hours, and 37 minutes. It rotates on a tilt, just like the Earth does, so it has four different seasons. However, these seasons are quite different from the seasons on Earth. Winter, spring, fall, and summer would all be freezing cold because it is always freezing on Mars. Mars is too far away from the sun to get enough energy from the sun's light, and the atmosphere is much too thin to keep the warmth inside. The usual temperature on Mars is usually about 81 degrees below zero, and in the summer, the temperature goes up about 32 degrees. Because it is so cold on Mars, carbon dioxide freezes in the winter and makes a lot of dry ice.

On earth, there is much liquid water, but people have not found any liquid water on Mars. Scientists think that all of the water on Mars is frozen. The summer in Mars is warm enough to get rid of the dry ice, but it is not warm enough to melt the ice that is made of water. Scientists think that the rest of the water on Mars is permanently frozen in the ground (permanently frozen ice is called permafrost, so there's a lot of permafrost in Mars!). However, Opportunity rover has found a rock formation on Mars which suggests that the rocks might have been in salt water once. The Spirit rover also found traces of a mineral called jarosite, which is made in liquid water. So there is some evidence that liquid water did, once, exist on Mars (this means that Mars must have been much warmer long ago).

Even though Mars is really cold, it's actually closer to the Earth's temperature than any other planet in the Solar System. This is the reason lots of people think of sending humans to Mars one day, and dream of building an artificial ecosystem that will protect people.

Martian Atmosphere

Mars has a very thin atmosphere with barely any oxygen (it is mostly carbon dioxide). Because there is an atmosphere, however thin it is, the sky does change colors when the sun rises and sets. The dust in the Martian atmosphere make the Martian sunsets have a rather blue color. Mars's atmosphere, of course, is too thin to protect Mars from meteors well, which is why the bottom half of Mars has so many craters. Some craters hit Mars with so much force a few pieces of Mars went flying into space - even into Earth! People have actually found rocks on Earth that have chemicals in them - chemicals that are like the ones in Martian rocks. These rocks also look like they fell really quickly through the atmosphere, so it is reasonable to think they came from Mars.

Martian Geography

Mars is home to the highest known mountain in the Solar System, Olympus Mons. Olympus Mons is about 17 miles (or 27 kilometers) high. This is more than three times the height of Earth's tallest mountain, Mount Everest.

Popular culture

Some famous stories were written about this idea. The writers used the name "Martians" for intelligent beings from Mars. In 1898 H. G. Wells wrote The War of the Worlds, a famous novel about Martians attacking the Earth. In 1938, Orson Welles broadcast a radio version of this story in the United States, and many people thought it was really happening and were very afraid. Beginning in 1912, Edgar Rice Burroughs wrote several novels about adventures on Mars.

Today

As of February 2011, scientists have not found life on Mars, either living now or extinct. Several space probes without people have gone to Mars to study it. Some have orbited (gone around) the planet, and some have landed on it. There are pictures of the surface of Mars that were sent back to Earth by some of these probes. Some people are interested in sending astronauts to visit Mars. This would be difficult. The astronauts would be in space for many years, and it could be very dangerous because of radiation from the sun.

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វិគីមេឌា Commons មានមេឌា​ដែលបានទាក់ទងនឹង:

Mars

• Mars at Space Wiki
• Mars at ESA/Hubble
• Mars Profile by NASA's Solar System Exploration
• Mars - About Space
• NASA's Mars fact sheet
• Mars Research News
• Planets - Mars A kid's guide to Mars.
• Mars
• Canals of Mars