Some Data and Concepts About Mars

Seasons Water

Life Dust Storms and Dust Devils

Seasons

As Mars, just like at Earth, seasons are due to the planet's axis tilt. On the other hand, Mars orbit's larger eccentricity is playing a role too. Mars' axis is tilted by 25.19°, that is barely more than Earth's. Hence northern and southern hemisphere are alternately tilted toward the Sun. Sun rays either graze or hit vertically the surface, defining winter and summer. Mars' orbit eccentricity is more accentuated than Earth's however and seasonal changes are sharper on Mars than on Earth. When Mars is at its perihelion (nearest to the Sun) it is 128,400,000 miles (1.36 AU) from the Sun, as at its aphelion (farthest from Sun) distance is 154,900,000 miles (1.64 AU). Like on Earth, northern summers are taking place at the aphelion as northern winters at the perihelion. From this, Southern summers are warmer. Like at Earth, seasons are termed solstices (summer and winter) and vernal and autumnal equinoxes (spring and fall). Mars has two polar caps which form and shrink according to the seasons. Due to difference in revolutions (Mars orbits in 687 days, Earth in 365), seasons are longer than Earth's by nearly an average of 100 per cent more. Spring is 93 days on Earth, 171 on Mars, Summer, 94 and 199, Autumn 89 and 171, Winter 89 and 146. There is a larger disparity between martian summer and winter due to the eccentricity of the orbit too. Seasons on Mars also induce carbon dioxide (CO2), which is the main component of martian atmosphere, to freeze into polar caps during winter and to vaporize during summer. When the southern polar cap thaws, it's liberating more CO2 than the northern one due to the warmer southern summers. This is leading to variations in Mars' atmospheric pressure as more gas is liberated at this period. Clouds exist at Mars, although less numerous than at the Earth. Dust clouds appear low in the atmosphere, as water clouds from near the surface up to about 12 miles (20 kilometers). Carbon dioxide clouds are seen at very high altitudes

Water

As far as question of water is concerned, one school deems Mars always was a warm, dusty, and dry planet, with a thin and cold atmosphere which did not retain liquid water. Hence martian water stayed frozen in martian soil for billions years. Another school sticks to a more conventional vision, one of a planet scoured by floods of waters and even having had an ocean in its northern part. Hence a dynamic and hydrologically active Mars all along its history.

A stunning view: frost as seen by Viking 2 in 1979 at Utopia Planitia. Although frost is no more than one-thousandth of an inch, it leaves dust and water on the terrain when evaporating. Another cycle of water? picture courtesy NASA "Mars for Press"

Observations made at Mars are showing river-shaped channels at Mars surface. But it seems that Mars quickly lost its atmosphere to the point of making the planet rapidly dry. Further, no limestone deposits -which would be a strong evidence of interaction between large amounts of water and atmosphere- have been found and olivine is abundant -that is a rock which does not last in the presence of water. Some explanations have been brought about such conflicting data. Water-shaped features would have been carved at an epoch dating back to what is called the "heavy bombardment period", when solar system formation leftovers heavily pondered newly formed planets. At Mars such impacts would have melt the underlying water-ice, sending it along with heated rocky material into the atmosphere. At such moments, Mars got warmer, more water-ice was vaporized, and a water-charged atmosphere triggered heavy localized rains. Each such period was followed by a back to a dry period. On the other hand, other processes may contribute to create watery related-looking relief features, such as volcanism, orbital and axis tilt variations (as they accentuate seasonal phenomenons), or even erosion by a mix of carbon dioxyn snow, dust, sand, and dry ice avalanching on carbon dioyin cushions. At last, some residual geological water-related processes are at work at Mars anyway, and are still nowaday. Most of Martian water is found about 18 inches deep as regions of long-lived hydrothermal activity exist where Martian magma is interacting with buried water-ice. This is generating possible limited water flows along million years, which would have yielded those gullies seen at some crater's edges

More About the Subsurface Structure and Ice Polar Layers at Mars!
New observations from NASA's Mars Reconnaissance Orbiter working in orbit At Mars indicate that the crust and upper mantle -or lithosphere- of Mars are stiffer and colder than previously thought. The thicker the lithosphere, the more gradually the temperatures increase, leading to that any aquifer below is now due to be found lower than thought. The discovery was made using the Shallow Radar instrument on the spacecraft, providing for views of the interior of Mars. The observations support too the idea that the north polar ice cap is geologically active and relatively young, at about 4 million years, with ice layers stretching up to 600 miles (1,000 kilometers) as previous studies had revealed that the thickness, in some places might reach 2,3 miles (3,7 km) -should such a material of ice melting, it would soak Mars under a water layer of 33 ft (11 meters). In-depth study of those layers also reveal four zones of finely spaced layers of ice and dust separated by thick layers of nearly pure ice, as such a pattern hints to cycles of climate change on Mars on a time scale of roughly one million years, caused by variations in the tilt of the planet's rotational axis and in the eccentricity of its orbit around the sun. The icy past of Mars too is linked to impact events

A Lot of Water at Mars in the Ancient Times!
Results of observation in 2008 are showing that there really was a lot of water flowing at Mars, during what is called the 'Noachian' period of Mars geological history -4.6 billion to 3.8 billion years ago that is. Large amounts of clay matching that period have been observed at the Red Planet

Some other data have been collected about water at Mars. There are evidences that deep underground Martian rocks are more water-rich than similar rocks at Earth. During Mars formation, melted magma, which contained important amounts of dissolved water (at least 3 percent) under great pression, had this water trapped when it cooled down. Most recent Mars Odyssey data are pointing too at Mars just coming out of an ice age. Hence underground water-ice would part into a deep, ice-rich layer -mark of the ice age, a middle layer with ice mixed to soil -that is the mark of a warmer era, and a dry soil layer topping both, as a result of dust left by as water ice vaporized

Life

As far as life on Mars is concerned, 1976 Viking missions, which were specifically designed for such a search, did not find any evidence of life. Mars would be self-sterilizing due to ultraviolet radiations, soil extreme dryness, and soil oxidizing mechanisms. It is thought however that life might have appeared or still exist at places protected against those martian defects such as in ice-water rich polar regions (where life similar to which seen in Antarctica might be found) or in undergroung regions of hydrothermal activity. One of the more intriguing fact is obviously ancient traces of life which were found on a martian rock having travelled as a meteorit down to Earth)

Dust Storms and Dust Devils

Martian storms whatever their size are sun-powered. Sun is heating the atmosphere, this in turn stirring up martian dust. When Mars approaches its perihelion (its nearest to the Sun, at southern summers) there is a larger potential for dust storms. Mars receives then 20 per cent more of sun energy than usual. Largest storms occur one to two months after perihelion. A lesser peak is already seen when the planet nears perihelion. Two places are known to be the birthplaces for dust storms: Hellas, and Thaumasia (region around Solis Lacus), as Lybia -east of Syrtis Major- is too. Dust storms, usually, are of the regional type, which means they usually concern a part of the martian disk only. Some may reach up to one-fourth of the planet's diameter however. Dust storms may sometimes turn into major and global dust storms, which are shrouding the entire planet for weeks

Martian dust devils are these spiraling columns of dust which are traversing the landscape where they are occurring. Dust devils at Mars are considerably larger than at Earth. They may reach 500 m wide and several thousand meter high as their terrestrial counterparts are about 10-100 m wide only (with winds circling the warm air column at about 20-60 mph (32-96 kph). Martian dust devils are an important erosion factor. They are transporting large quantities of dust. Dark (or light) track patterns are commonly found in many Mars regions and are changing from season to season. Dust devils at Earth are featuring large electric fields in excess of 4,000 volts/meter or more, and magnetic fields. It is still unsure, but likely that Martian dust devils have these same characteristics. for more about Martian dust devils, see this page about the hazards they might cause to surface expedition