- kcLv 51 十年前最愛解答
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.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 a year on Mars. Three Mars orbiters (Mars Global Surveyor, 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).
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.
- 匿名1 十年前
Mars is the fouth planet in the solar system
- nonenoneLv 41 十年前
Mars is the fourth planet from the Sun. The planet is named after Mars, the Roman god of war. Mars is also known as “The Red Planet” due to its reddish appearance as seen from Earth. The prefix areo-, from the Greek god of war, Ares, refers to Mars in the same way geo- refers to Earth.
Mars has two moons, Phobos and Deimos, which are small and oddly shaped. These may be captured asteroids similar to 5261 Eureka, a Mars Trojan asteroid. Mars can be seen from Earth with the naked eye. Its apparent magnitude reaches −2.9, a brightness surpassed only by Venus, the Moon, and the Sun. For much of the year, Jupiter may appear brighter to the naked eye than Mars.
Until the first flyby of Mars by Mariner 4 in 1965, it was hoped, both within and outside scientific circles, especially in the popular media and literary circles, that Mars had ample liquid water. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, and long dark striations that could perhaps even be irrigation channels of liquid water.
These straight line features were shown not to exist and explained as optical illusions. Still, of all the planets in our solar system other than Earth, Mars is the most likely to harbor liquid water, and perhaps life. Mars' rotational period and seasonal cycles are also similar to those of the Earth. It has the highest mountain in the solar system, Olympus Mons, the largest canyon in the solar system, Valles Marineris, and polar ice caps. Geological evidence suggests that Mars previously had large-scale water coverage, while observations also indicate small geyser-like water flows in recent years.
Mars is currently host to four orbiting spacecraft: Mars Global Surveyor (non-functional), Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. This is more than any planet except Earth. It is also home to the two Mars Exploration Rovers (Spirit and Opportunity). Recent evidence from NASA's Mars Global Surveyor, shows evidence that southern polar "ice" cap has been receding.
The red/orange appearance of Mars' surface is caused by iron(III) oxide (rust).