The largest craters or impact basins on Mars may be buried beneath the northern smooth plains.

In the southern hemisphere, the bombardment history typical of all the inner planets is recorded by a few large basins, such as Argyre.

The ring of mountains surrounding the basin probably rises 5 kilometers above the basin floor.

A large dark area. The Elysium volcano, a yellow area north of Cerberus, has several channels radiating from its flanks.

The geological structures of Cydonia has replaced the canals as object of controversy. They are several small mesa with sloping

sides located at the northeast of the Cydonia Mensae. They stand amid the plains looking like islands that resisted water erosion,

view from certain angles they look like artificial constructions and have received evocative names like the Face, the Pyramid,

the Forteress, the Channel.

In Greek mythology, Deimos is one of the sons of Ares (Mars) and Aphrodite (Venus); "deimos" is Greek for "panic".

Diameter: 12.6 km (15 x 12.2 x 11)

An impact crater in the southern hemisphere over 6 km deep and 2000 km in diameter.

An important depression nearby Kasei Canyon system, one of the lowest place on Mars

The largest mountain in the Solar System rising 21 km ( 69,000 ft.) above the surrounding plain. Its base is more

than 600 km in diameter and is rimmed by a cliff 6 km (20,000 ft) high.

Olympus Mons is an extinct volcano and the largest known volcano in the solar system. Atop this implausible mountain is

the equally stupendous caldera composed of nested craters 80 km across and 3 km deep.

The slopes below the summit are made up predominantly of lava flows. The lava which poured out of Olympus Mons

was very fluid and spread readily down the shallow gradients, accumilating to form the main body of the mountain.

Around the base of Olympus Mons is a roughly circular ring of cliffs which were clearly produced by erosion.

However, basalt flows do not erode in this fashion. Thus the outer portions of Olympus Mons must be composed of some other material. The most likely material is compacted ash, and if this interpretation is correct the ash was probably transported the vast distances involved within a cloud of hot gas. The erosion agent would have been wind.

In Greek mythology, Phobos is one of the sons of Ares (Mars) and Aphrodite (Venus). "Phobos" is Greek for "fear" (the root of "phobia").

Phobos is the larger and innermost of Mars' two moons. Phobos is closer to its primary than any other moon in the solar system, less than 6000 km above the surface of Mars.

Orbit: 9378 km from the center of Mars

Diameter: 22.2 km (27 x 21.6 x 18.8)

Mass: 1.08e16 kg

Phobos is doomed, because its orbit is below synchronous altitude tidal forces are lowering its orbit. In about 50 million years it will crash onto the surface of Mars or break up into a ring.

One of the most Earth like features of Mars are its polar ice caps, which are believed to be made of frozen carbon dioxide (dry ice) sublimating from the atmosphere lying over water ice. They constitute an important natural reserve of water which could prove fundamental to future settlement of the planet.

Winters in the southern hemisphere are both longer and colder than winters in the northern hemisphere. Because of that, the south polar cap is larger than the Northern polar cap and it does not recede totally during the southern summer, while the northern cap is completely vaporized onto the atmosphere.

The polar regions present seasonal variations and unique laminated deposits which are a testimony to the climatic history of the planet. Since the density of craters in this regions is very low, they are believed to be the youngest surfaces on the planet.

The north pole is surrounded by a system of dunes and the south pole is believed to lie over an impact basin of 850 km across.

A huge bulge on the Martian surface that is about 4000 km across and 10 km high.

Valles Marineris is a system of canyons located just south of the Martian equator. The system is about 4000 km long. The central individual troughs, generally 50 to 100 km wide, merge into a depression as much as 600 km wide.

In places the canyon floor reaches a depth of 10 km, 6 times deeper than the Grand Canyon. The geologic history of the central canyon system is complex: first the surface collapsed into a few deep depressions that later became filled with layered material, as lake deposits.

Then graben forming faults cut across some of the older troughs thus widening existing troughs, breaching barriers between troughs, and forming additional ones. At that time the interior deposits were locally bent and tilted, and perhaps water, if still present, spilled out and flowed toward the outflow channels.

Huge landslides fell into the voids created by the new grabens. Wind-drifted material, mostly dark in color, apparently still moves along the canyon floor and locally forms conspicuous dunes.

Other bacteria, for example thermophilic bacteria, prefer scalding hot temperature and thrive within hot springs, both on land and on the ocean floor. However, their metabolic optima are usually very close to their upper temperature limit - a few degrees above and they are killed.

The range of tolerable temperatures for multicellular organisms is much more restricted. Plants and most animals fall under this category. Many plants not specifically adapted to cold and suffer fatal frost damage by one night's exposure to 0 degree Celsius. In general, productive photosynthesis requires temperatures of >0 degrees Celsius and preferably >10 degrees c.

The optimum range for germination of most seeds and growth of most plants is 10-40 degrees c.

Thus, while microorganisms can survive and reproduce successfully in extreme environments, plants cannot. These temperatures ranges are very similar to those tolerable by animal life, which is hardly surprising since plants are the basis of the food chain.

Homo Sapiens have shown a particular ability to cope with temperature variations and are thus found in more varied locales than any other animal species. This is, of course, because of one of our earliest technological inventions- clothing.

At high temperatures, the relative humidity of the air becomes an equally important factor; above human body temperature (37ºC) evaporative heat loss via perspiration must take on the entire burden of thermostasis and this cannot occur if the air is already saturated with water vapor (100% relative humidity).

As temperature increases, relative humidity must be reduced and the time of exposure lessened to avoid hyperthermia. For instance, people can just about withstand 50% for 24 hours, but any longer than this would require lowering the temperatures, humidity, or both.

Humans cannot exist remote from the ecosystems that provide life support. Taking this into account, a mean average temperature range of 0-30ºC seems reasonable for sustainable human habitability, so long as most extreme of seasonal variations do not take daily average temperatures much in excess of 40ºC or far below -10ºC.

The key environmental problem with Mars is not that it is so cold, but that the air is so thin. It has been said already that the average atmospheric pressure at the zero datum is less than 1% that of Earth.

The Martian atmosphere is very tenuous. The average surface pressure on the surface of Mars is of about 8 millibars, the equivalent of an altitude of 30,000 m above sea level on Earth.

Again because of the very low atmospheric pressure, liquid water, essential to the development of any life form, is not stable on the surface. Combined with the low Martian temperatures, water would freeze instantly.

Because of extremely low pressure, although the amount of water is very small in the Martian atmosphere, it is always close to saturation. Formation of clouds and fogs is a very common feature in the Martian atmosphere.

A unique phenomenon on Mars is that 30% of the atmosphere condenses each Martian winter on the winter pole; which are thus mostly made of frozen carbon dioxide, although scientists strongly suspect that water ice is lying underneath the dry ice.

This creates an area of extremely low pressure that determines general patterns of wind circulation from areas of relatively high pressure at the equator towards the winter pole.

The general trend is that warm air rises over the summer hemisphere and circulates towards the winter hemisphere. Circulation is further complicated by the global dust storms which can arise again due to low pressure that allows suspension of dust and other particulate materials.

Because of the absence of the moderating effect of the oceans, the surface is very responsive to temperature gradients. Diurnal temperature variations of 70° were measured as well as peak temperature gradients of 20° per minute in the morning.

However, the isotopic composition of the atmosphere, especially the inert gases, constitutes evidence to the fact that in the early days of the planet the atmosphere was substantially different to the one that can be measured now by spacecraft. Nitrogen, oxygen and carbon could escape the Martian atmosphere in a very slow process.

The isotopes of these elements to escape would naturally be the lighter ones and consequently, the relative abundance of the isotopes of each element would shift towards the heavier isotopes at surface level. Measurements of the current relative abundance of the heavier and lighter isotopes of those elements can yield very interesting information about the planet's past.

There is expected to be a wide range of atmospheric pressure consistent with habitability; the total barometer pressure consisting of tolerable partial pressures of essential constituents, such as nitrogen, oxygen, carbon dioxide and water vapor. This is especially so for microorganisms with their extraordinary adaptability and metabolic variety.

For example, bacteria have demonstrated the ability to tolerate and metabolize gaseous compound that would be dangerous to higher organisms such as hydrogen, ammonia, methane, and hydrogen sulfide. For a sustainable bacterial ecology, nitrogen fixation will be required and it has been estimated that the organisms responsible could carry out this process at pN2 between 1-10 mbar, much less than the 790 mbar in the Earth's present atmosphere.

The minimum total atmospheric pressure that might be consistent with bacterial habitability would be made up from water vapor in equilibrium with an average planetary temperature of ~0ºC (~6 mbar) plus essential amounts of N2, O2, and CO2.

More salubrious conditions are needed by higher plants which are complex aerobic organisms that evolved in concert with animals. They are limited in their function by both pCO2 for photosynthesis and pO2 for respiration-the necessity for the latter is sometimes overlooked as it is easy to assume that since plants evolve O2 as they grow, they are never limited by oxygen deficiency.

Humans from all civilizations have been watching Mars for hundred of years and have translate their fears and questions about the red planet into their cosmology and myths; in general they associate Mars with fire, blood, war and danger. You will find here under, some of the myths and Gods related to Mars in Earth's history...