Mars

Mars is the fourth planet in the solar system, named for the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color.

Physical characteristics

Mars has always fascinated people. Its red, fiery appearance was mysterious and intriguing. Mars has only a quarter the surface area of Earth and only 1/10th the mass (though because it lacks oceans the area of Mars' accessable dry land is approximately equal to that of the Earth's dry land). Mars has two small moons, Phobos and Deimos, both small and oddly shaped, possibly captured asteroids. Mars has polar ice caps that contain frozen water and carbon dioxide. An extinct volcano, Olympus Mons, is, at 25 km, the tallest mountain in the solar system. Mars' atmosphere is very thin, the surface air pressure is only 7.5 millibars compared to an average 1013 millibars on Earth. The atmosphere on Mars is 95% carbon dioxide, 3% nitrogen, 1.6% argon, with only a trace of oxygen and water.

Mars has an important place in human imagination due to the old belief that life existed on Mars. This was supposed because of observations of linear features on the surface that appeared artificial and seasonal changes in the brightness of some areas that were thought to be caused by vegetation growth. This gave rise to many stories concerning Martians. The linear features are now know to be non-existent or in some cases, ancient dry watercourses. The color changes have been ascribed to dust storms. Recently analysis of meteorites thought to have come from Mars show some features that may be fossils of single celled organisms.

http://meta.wikipedia.com/upload/marsglobe1-thumb.jpg

Global mosaic of Mars. Visible in the center of this mosaic is the largest known chasm in the solar system, Valles Marineris. To the left of the image are the volcanoes of the Tharsis bulge. click here for full-sized image

Mars Facts:

equatorial diameter: 4,212.28 miles (6,794 kilometers)
mass: 6.4191×10²³ kg (0.11 of the Earth)
mean relative density: 3.95
surface gravity: 0.38
surface area relative to Earth: 0.28 (144 million km²)
farthest distance from the Sun: 154,900,000 miles (249,200,000 kilometers)
closest approach to earth approx.: 48,700,000 miles (78,390,000 kilometers)
orbital period: 687 earth days
rotational period: 24hrs. 37mins.
low temperature: -305 F (-187 C)
satellites : 2, Phobos (from Greek Fear) and Deimos (from Greek Panic)

Mars's moons

Phobos
- Orbital radius: 9378 km (note: measured from the center of Mars)
- Diameter: 22.2 km (27 x 21.6 x 18.8)
- Mass: 1.08×10¹⁶kg
- Orbital period: 0.31910 days (7.66 hours)
- Rotational period: 0.31910 days (7.66 hours)
- Density: 2.0 g/cm³
- Orbital inclination: 1.0°
Deimos
- Orbital radius: 23,400 km
- Mass: 2×10¹⁵ kg
- Rotational period: 30.35 hours
- Orbital period: 30.35 hours
- Dimensions: 10 km X 12 km X 16 km

Both Phobos and Deimos are tidally locked with Mars, always pointing the same face towards it. Since Phobos orbits around Mars faster than the planet itself rotates, tidal forces are slowly but steadily decreasing its orbital radius. At some point in the future Phobos will impact on Mars' surface. Deimos, on the other hand, is far enough away that its orbit is being slowly boosted instead.

The exploration of Mars

Many robotic probes have been sent from Earth to Mars, with a few spectacular successes and a notably high failure rate. Some of the failures can be ascribed to technical incompetance, but enough others have failed for no apparent reason for researchers to half-jokingly speak of an Earth-Mars "Bermuda Triangle" or of a Great Galactic Ghoul which subsists on a diet of Mars probes.

Two Soviet flyby probes were launched towards Mars in October 1960 but failed to reach Earth orbit. In 1962, three more Soviet probes failed -- two remaining in Earth orbit and one losing communication with Earth en route to Mars. In 1964, there was another failed attempt to reach Mars.

Between 1962 and 1973, NASA's Jet Propulsion Laboratory designed and built 10 spacecraft named Mariner to explore the inner solar system. These spacecraft were designed to visit the planets Venus, Mars and Mercury for the first time. They would then return to Mars for additional close observations. The Mariners, relatively small robotic explorers, were launched on Atlas rockets. Each weighed less than half a ton.

Mariner 3 and Mariner 4 were identical spacecraft designed to carry out the first flybys of Mars. Mariner 3 was launched on November 5, 1964, but the shroud encasing the spacecraft atop its rocket failed to open properly. Mariner 3 failed to reach Mars. Three weeks later, on November 28, 1964, Mariner 4 was launched successfully on an eight-month voyage to the red planet.

Mariner 4 flew past Mars on July 14, 1965, providing the first close-up photographs of another planet. The pictures, played back from a small tape recorder over a long period, showed lunar-type impact craters. Some of them seemed touched with frost in the chill Martian evening.

In the 1970s the Viking probes orbited and landed on Mars, returning the first color pictures and extensive new scientific information. The Soviet probes of the Mars probe program attempted a number of landings several years before Viking, but were not nearly as successful.

Next came Mars Global Surveyor. This mission was the first successful one to the red planet in two decades when it launched November 7, 1996, and entered orbit on September 12, 1997. After a year and a half trimming its orbit from a looping ellipse to a circular track around the planet, the spacecraft began its primary mapping mission in March 1999. It has observed the planet from a low-altitude, nearly polar orbit over the course of one complete Martian year, the equivalent of nearly two Earth years. Mars Global Surveyor recently completed its primary mission on January 31, 2001, and is now in an extended mission phase.

The mission has studied the entire Martian surface, atmosphere, and interior, and has returned more data about the red planet than all other Mars missions combined. This valuable data is archived at http://wufs.wustl.edu/missions/mgs/mola/ .

Among key science findings so far, Global Surveyor has taken pictures of gullies and debris flow features that suggest there may be current sources of liquid water, similar to an aquifer, at or near the surface of the planet. Magnetometer readings show that the planet's magnetic field is not globally generated in the planet's core, but is localized in particular areas of the crust. New temperature data and closeup images of the Martian moon Phobos show its surface is composed of powdery material at least 1 meter (3 feet) thick, caused by millions of years of meteoroid impacts. Data from the spacecraft's laser altimeter have given scientists their first 3-D views of Mars' north polar ice cap.

Several other recent probes from the United States and Russia have failed upon arrival at Mars.

The International Astronomical Union's Working Group for Planetary System Nomeclature is responsible for naming Martian surface features.

Many people, from Werner Von Braun on, have long advocated a manned mission to Mars as the next logical step for a manned space program. As well as the undeniable romanticism of human exploration, such advocates believe that the amount of scientific work able to be performed in a human mission would be far superior than that possible with robotic explorers, thus making the large cost of a manned mission justifiable. With present technology, Mars Direct, forcefully advocated by Robert Zubrin of the Mars Society, is believed by many as the most practical and affordable plan for a manned Mars mission.

Longer term, some scientists believe Mars top be a good candidate for terraforming and human colonization, though other prominent skeptics (such as Robert Park) hotly dispute its practicality.

Recent findings by the Mars Odyssey probe's gamma ray spectrometer and neutron spectrometer have determined that there are vast deposits of water ice in the upper three meters of Mars' soil within 60° lattitude of the south pole. Similar quantities of ice are expected to be present in the north polar region as well, but measurements will not be made until later in 2002.

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This image was acquired at the Viking Lander 1 site with camera number 1. The large rock just left of center is about 2 meters wide. This rock was named "Big Joe" by the Viking scientists. The top of the rock is covered with red soil. Those portions of the rock not covered are similar in color to basaltic rocks on Earth. Therefore, this may be a fragment of a lava flow that was ejected by an impact crater. click here for full-sized image