Thursday, October 11, 2007

The real facts about Mars

Mars (Greek: Ares) is the God of War. The planet perhaps got this name due to its red color; Mars is at times referred to as the Red Planet. The name of the month March obtains from Mars.

Mars has been recognized since prehistoric times. Certainly, it has been broadly studied with ground-based observatories. But even very large telescopes find Mars a hard target, it's just too small. It is still a favorite of science fiction writers as the best place in the Solar System (other than Earth!) for human habitation. But the illustrious "canals" "seen" by Lowell and others were, regrettably, just as fantasy as Barsoomian princesses.

Mars' orbit is considerably elliptical. One result of this is a temperature variation of concerning 30 C at the sub solar point between aphelion and perihelion. This has a most important influence on Mars' climate. While the average temperature on Mars is about 218 K (-55 C, -67 F), and in summer, Martian surface temperatures range broadly from as little as 140 K (-133 C, -207 F) at the winter pole to roughly 300 K (27 C, 80 F) on the day side.

There is dreadfully clear evidence of erosion in many places on Mars together with large floods and small river systems. At some time in the past there was evidently some sort of fluid on the surface. Liquid water is the clear fluid but other possibilities exist. There possibly will have been large lakes or even oceans; the proof for which was strengthened by some extremely nice images of layered terrain taken by Mars Global Surveyor and the mineral logy results from MER Opportunity. Most of these points to wet episodes that occurred only for a short time and very long ago; the age of the erosion channels are estimated at about almost 4 billion years. However, images from Mars Express released in early on 2005 show what appears to be an ice-covered sea that was liquid very recently (maybe 5 million years ago). Confirmation of this interpretation would be an extremely big deal indeed!

Mars has a very thin atmosphere composed more often than not of the tiny amount of remaining carbon dioxide (95.3%) plus nitrogen (2.7%), argon (1.6%) and traces of oxygen (0.15%) and water (0.03%). The average pressure on the surface of Mars is simply about 7 millibars (below 1% of Earth's), but it varies to a great extent with altitude from almost 9 millibars in the deepest basins to about 1 millibar at the top of Olympus Mons. But it is thick enough to support very strong winds and measureless dust storms that on occasion engulf the entire planet for months. Mars' thin atmosphere produces a greenhouse consequence but it is only enough to lift up the surface temperature by 5 degrees (K); much less than what we observe on Venus and Earth.

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