Mars atmosphere
[ mars atmosphere.doc ]
If we are looking today on Mars we can notice that its atmosphere is absolutely transparently and very thin. We don't see any clouds of water vapor. Clouds that are found on the planet surface are made mainly from carbon dioxide and dust.
Rys1.
Convection streams, existing in Mars atmosphere are too weak to create perturbations of the weather. Dust storms, which can be very long, are blocking observations of the martian surface, were made under assembly of interaction of the vertically convection streams in atmosphere and the interaction of the Coriolis force on the mass concentrated in the cloud. Taking into nocnsideration that the medium atmosphere temperature is low, circa -65oC, the maximal volume size of the dust moved up in the cloud also is limited. The dust is of the order of few microns. The small gravity of the planet causes that the duststorms are longre in time that their cousins on Earth. Turning of the clouds also provide moving of the weather perturbations over large regions on Mars.
Rys2.
But the superior question is: why Mars has this weakened atmosphere ?
To get an answer we have to get back to the most critical moments of Mars history. The collisions which large cosmic bodies.
Those collisions have made radical changes on Mars surface. In this time were made gigantic impact craters Argrye and Hellas, the huge volcanic caldera Alba Patera was moved up, vulcans from the Tharis massive and Olympus Mons have been activated. Moreover, the gigantic rift valley Valles Marineris was created.
Impacts have had also an influence on the internal structure of the planet. Nucleus, probably primary considerably cooled, was heated again thus providing off the heat which has been made under a friction with body(ies) that have penetrated Mars interior. Perhaps it was the cause of the destruction of original planet's magnetic dipole, and in long time this supporting heat in martian interior, self-contained its activity but with small intensity. That could have worsened conditions to the point that the planet was unable to hold a dense heat atmosphere.
Mars has almost three times smaller gravity force than Earth, its surface (an ideal sphere) is several times smaller than earth's surface. So, considering all events we have to keep in mind its dimensions.
The question of Red Planet atmosphere touches many aspects. We don't know the original composition of Mars atmosphere. Supposing, that its history of creation is similar to earth's history, we should use some simplifications and generalizations. It's not the strategy of using the shortest way, we just lack informations. We dont have any reliable point of view on martian history before impact(s) with critical body(ies).
Rys 3.
All terrain features we can see today on Mars have traces of this impact.
Is the present Mars atmosphere a result of this impact ?
Yes, without any doubt.
What could happened with a origin atmosphere ?
Looking for an answer for this question we have to see the Mars history from two points of view.
Geologically, that get us an answer for the impact(-s) which created the present state - impact with a critical body and have made changes of planets nucleus. That take effect of changing magnetical, gravitional and thermodynamic conditions afecting the dense atmosphere [1].
Second point of view, that is a test estimation of phenomena's which could have happened in Mars atmosphere during and just after the impact(-s).
The phenomenon scale is similar only to the effects of the famous Yucatan impact that caused the dinosaur extinction 65 mln years ago..
Mars have this "bad luck", that he has been and still is to small. Its gravity is three times smaller than the Earth's and the body he has been hit by was without any doubt much larger than the asteroid that have hit Yucatan..
Red Planets atmosphere inthe time of impact was completely troubled, probably strongly heated, extend its volume, considerably over a stability magnetically-gravitionally-thermodynamic equilibrium. Hard to imagine impacts waves of dust and gases surrounded Red Planet many times. Under collisions they created special zones of fronts, where directions of the pressures were directed in each way, and only one direction, to space, allowed escape of for the energy. That could made a specially traces those impacts on Mars surface. Zones of condense matter with strongly changed physical and chemical properties.
It is sure that the impact have rapidly vaporized tons of rocks, both original Mars rocks and the impact body, and moved up a lot of matter (dust).
Those gases in first time have been strongly heated (in this time they could be totally ionized), perhaps had been brought into open space, where, under fast cooling they could made gas clouds. However due to strong interaction of the solar wind and lack of strong planet magnetic field that could partially imprison them, they had moved outside present Mars orbit around the Sun.
Dusts were brought into space, as a result of big energy provided by the impact. It is difficult to say how much mass had moved up and vaporized during the impact. Therefore an assessment what part were dusts is difficult. However, there is one possibility to find an answer for this question.
Where ?
On the Martian moons, Phobos and Deimos.
Rys 4. Phobos
Rys 5. Deimos
We don't know exactly how long they are staying on Martian orbit, but we can suppose that they stay there enough time to gravitionally absorb those rest part of gases and dusts moved up during the impact, and which hadn't escaped into interplanetary space.
Last successfully landing NEAR probe on Eros asteroid suggest that it is technically possible to make a landing on objects with little gravity.
Non concerned with technically details, we can find reasons for this kind of mission.
1. Analysis of the chemical fractional composition of both moons. Phobos and Deimos have very small albedo. Covered by strong break-up dust have visibility as ideally black bodies. Black dust, which have covered them could have in the past a heat treatment from the thermal energy that have been emitted in time of Mars impact with critical body.
2. Verification of the physical and mechanical properties of the cover layer and core drilling to taking geological samples. If original moon material have been made in other conditions than its cover layer, cover layer and core samples will be very different.
3. Near orbiting around the moons to check potential anomalies of gravity and magnetic field. If those moons, especially Phobos, were staying on Mars orbits in time of impact with w critical body, thermal and radio emission of impact could made a structure changing of undersurface layer of moons. Especially magnetical and electrical conductivity. That depends on what was their position during the impact.
What kind of connection there is between Mars and its atmosphere ?
If those moons have been on Mars orbits in time of the impact with critical body, the absorbed dust could have imprisoned, structurally and chemically, particles of the origin planets atmosphere, which had heated by impact energy could surrounded Phobos.
Besides, investigations of the absorbed gases could close an answer for questions: what kind of space body was a critical body (asteroid or comet), what it have had of composition made, how big was roughly impact energy (massive elements could vaporized and ionized only in strictly described conditions of pressure and temperature) etc.
Source materials:
- Lewandowski K. Anomalie magnetyczne a geologia Marsa. http://chapters.marssociety.org/polska/anomalie.html
- http://www.gly.bris.ac.uk/www/teach/virtrips/nineplanets/phobos.html
- http://www.gly.bris.ac.uk/www/teach/virtrips/nineplanets/deimos.html
- Gilbert M.G. at all. Mars z bliska, National Geographic Maps for National Geographic Magazine 2/2001, edycja polska.
- NASA www.nasa.gov