1.10.3 Star Fleet Planetary Classification Scheme
What is observed when looking at these planets is the tops of clouds high in their atmospheres. The composition of Jupiter’s atmosphere is about 90% hydrogen, 10% helium (by mass, 75/25%) with traces of methane, water, ammonia and "rock", compared with the details given on Neptune above. Jupiter's atmospheric gases are very close to the composition of the primordial solar nebula from which the entire solar system was formed. Saturn has a similar composition, but Uranus and Neptune have much less hydrogen and helium.
Jupiter is believed to have three cloud layers in its atmosphere. At the top are clouds of ammonia ice; beneath that ammonium-hydrogen sulphide crystals; and in the lowest layer, water ice and perhaps liquid water. The origins of the colourful features such as the Great red Spot are uncertain, but scientists believe that they are caused by plumes of warmer gases that rise up from deep in the planet's interior. The plumes' colours are probably caused by their chemical content. Although the amount of carbon, for example, in the Jovian atmosphere is very small, carbon readily combines with hydrogen and trace amounts of oxygen to form a variety of gases such as carbon monoxide, methane, and other organic compounds. The orange and brown colours in Jupiter's clouds may be attributable to the presence of organic compounds, or sulphur and phosphorus and are low in water. The expectation was that Jupiter's atmosphere would contain about twice the amount of oxygen (combined with the abundant hydrogen to make water) as the Sun. The Sun has more recently been found to be far wetter than believed. The Galileo Probe that penetrated Jupiter's atmosphere in December 1995 found only a fraction of the water expected. Further analysis of the probe data has turned up additional surprises. Wind speed at the surface was clocked at 150 m/sec; at the lower depths the speed did not fall off but actually increased to 200 m/sec. Lightning at Jupiter was observed to be less frequent than on Earth. (The American Institute of Physics Bulletin of Physics News Number 272 May 23, 1996 by Phillip F. Schewe and Ben Stein). Jupiter is not the only planet with such high velocity winds and the other gas planets have similar velocity currents which are confined in wide bands of latitude. The winds blow in opposite directions in adjacent bands. Slight chemical and temperature differences between these bands are responsible for the colours that dominate the planet's appearance. The light coloured bands are called zones; the dark ones belts. The data from the Galileo probe indicate that the winds are even faster than expected (more than 400 mph) and extend down into as far as the probe was able to observe; they may extend down thousands of kilometres into the interior. Jupiter's atmosphere was also found to be quite turbulent. This indicates that Jupiter's winds are driven in large part by its internal heat rather than from solar input as on Earth. The colours correlate with the cloud's altitude: blue lowest, followed by browns and whites, with reds highest. Sometimes we see the lower layers through holes in the upper ones. Atmospheres are discussed in more detail below (physics of planetary atmospheres)
Jupiter radiates more energy into space than it receives from the Sun. The interior of Jupiter is hot: the core is probably about 20,000 K. The heat is generated by the Kelvin-Helmholtz mechanism, the slow gravitational compression of the planet. (This interior heat probably causes convection deep within Jupiter's liquid layers and is probably responsible for the complex motions we see in the cloud tops. Saturn and Neptune are similar to Jupiter in this respect, but oddly, Uranus is not. Jupiter's diameter is about as large as a gaseous planet can be. If more material were to be added, it would be compressed by gravity such that the overall radius would increase only slightly. A star can be larger only because of its internal (nuclear) heat source. (But Jupiter would have to be at least 80 times more massive to become a star.) Jupiter has a huge magnetic field, much stronger than Earth's. Its magnetosphere extends more than 650 million km, though not spherically.
Jupiter has faint rings like Saturn's, and were only discovered when two of the Voyager 1 scientists insisted that after travelling 1 billion km the space probe should attempt to look in the direction for the possibility of ring structures or ring arcs. Though the general consensus of opinion was against there being any such matter around Jupiter Voyager 1 succeeded in detecting rings. Unlike Saturn's, Jupiter's rings are dark (albedo about .05). They are most likely composed of very small grains of rocky material. Particles in Jupiter's rings are unlikely to remain there for long, due to atmospheric and magnetic drag. Therefore, if the rings are permanent features, they must be continuously resupplied. The small satellites Metis and Adrastea which orbit within the rings, are the obvious candidate sources.
Class Y planets are probably best associated with the Jovian Moon Io. It is likely that the main source of danger in the Class Y environment is the radiation, referred to as thermionic. though we cannot be certain about the specifics of this radiation we can compare this with the radiation on Io. Io itsef has a plasma torus where the ejecta from the surface are ionised by the Jovian magnetosphere. In addition to this Io is in a position whereby it is swept by the Jovian magnetic field once every 10 hours.
Other Classes and the Adaptability of Federation Facilities to Alternative Atmospheric Classes
The starbase Deep Space 9 is designed to allow many different races accommodation onboard. To facilitate this process the station has variable environmental capabilities within the occupants quarters. All rooms are equipped to handle class M environments with provisions for 25% of quarters to support class H, K and L environments. The transient facilities, those reserved for peoples passing through but not intending to stay abroad for any length of time, include 3% class B, N and C environments. We have no way of knowing if the atmospheric designations exactly match the planetary classifications but in the light of the details for Class M it would seem likely. Nominal Starfleet Class M ship operations as noted in Starfleet Standard 102.19 differ slightly from the actual class M environment used aboard the station. Deep Space Nine being designed to support Bajoran nationals and thus replicating the surface conditions of the planet as accurately as possible. Bajoran atmospheric values are kept maintained at 25 Celsius, 45% relative humidity, with a pressure of 99.7 kilopascals as opposed to SFRA standard 102.19 which maintains ships at 26 Celsius, 45% relative humidity with pressures of 10 kilopascals. The actual composition of the atmospheric gases is 77% nitrogen, 21% oxygen and 2% trace gases, mostly argon, helium and xenon. The Galaxy Class USS Enterprise NCC 1701 D, could support Classes H, K and L in 10% of its quarters with 2% equipped to handle N and N(2) conditions. It was possible using the facilities of a starbase to equip the vessel with ship wide Class H, K or L conditions.
The mention of Atmospheric classes B, N and C (see previous paragraph) suggests, logically, that there are at least three classes not listed here. No information is given about these classes but one might very well assume that they differ significantly from standard Class M given the small number of quarters capable of housing them. As life is linked to the development of an atmosphere these worlds might represent planets where evolution has developed significantly differently to Earth. They may even represents planets where biologically life does not exist and compounds other than carbon based life dominate. Starfleet has on a number of occasions encountered silicon based life and this may represent evolution within one or more of the environments.
Samuel T. Cogley cited the Fundamental Declarations of the Martian Colonies, along with the Bible, the Code of Hammurabi, and the Constitution of the United States of America as a historic milestone in the evolution of legal systems that protect the rights of the individual. Many of the Starfleet's ships were constructed and developed at the Utopia Planetia Ship Building facility. This was the birth place of USS Enterprise, the flag ship of the fleet.
| Gas | Proportions |
| Carbon dioxide | 95.32% |
| Nitrogen | 2.7% |
| Argon | 1.6% |
| Oxygen | 0.03% |
| Carbon monoxide | 0.07% |
| Water vapour | .03% |
| Neon | 2.5 ppm |
| Krypton | 0.3 ppm |
| Xenon | 0.08 ppm |
| Ozone | 0.03 ppm |
"Genesis is life from lifelessness." Carol Marcus 2284.
A project developed during 2280's by Carol Marcus and her son David Marcus but prematurely concluded in 2285. The project was designed to allow the recreation of planet surfaces, atmospheres and biospheres to Class M, habitable environments. Stage 1 of the testing was completed in a laboratory with Stage 2 being carried out less than 12 months later in the underground caverns of a lifeless planetoid Regula 1, a rock classed as a D type planet. The Genesis Proposal to the Federation showed a computer simulation. of the proposed Genesis Effect. The device would be deployed by a torpedo, presumably deployed from a starship's weapons system. Upon impact the device re-arranged matter on a subatomic level. It seemed the planet's mantle, core and even most crustal formation was left intact. The surface and any biosphere (should the device inadvertently be detonated on a habited planet) would be reformed in preference of the new matrix. Molecular matter was reorganized at subatmoic scale in favour of a life generating matter of equal mass. USS Reliant was assigned to be at the disposal of the Regula One observatory science crew. Reliant was scheduled to find an uninhabited planetoid for Genesis testing and report back three months later. Unfortunately, Reliant was captured at Ceti Alpha V and the testing was interrupted and subsequently prematurely detonated by the 20 century war criminal Kahn Noonian Singh.
The premature detonation of the genesis device in the Mutara Nebula seemed to condense the nebula gases into not only a planet but a stellar body as well. The Genesis Wave accelerated the development of the world and probably accounted for the fact that no pre-main sequence events were seen in the newly formed star. The planet aged rapidly due to the use of proto-matter in the Genesis matrix. This was against the consensus of opinion of the late 23rd century that maintained it was extremely hazardous.
Terraforming
Terraforming involves any large scale attempt to allow human(oid) life to survive on a previously uninhabitated world. This process either involved the use of bio-domes (see Mars/Lunar). Other more ambitious projects involve the complete restructuring of the atmosphere. Due to the implications that any terraforming would have on already existing life forms, the Federation employs very strict rules to protect indigenous life. Professor Gideon Seyetik was a renowned scientist having terraformed the planets New Halana and Blue Horizon the later being a particularly beautiful world.
It is believed that the planets formed via the aggregation of material from a nebula surrounding the protostar around 4600 million years ago. It has been theorised that the accretionary period took place while the nebula was very hot in excess of 1500° c. The planetessimal would begin to contract and the cloud’s heat would rise. Recent work suggests that this period of solar system formation could only occur in the presence of a nearby large X-ray gamma ray burst. Brian McBreen and Lorraine Hanlon of University College Dublin suggest that all the chondrules in the solar system formed within a matter of minutes when intense X-rays hit the gas and dust circling the primordial sun. (New Scientist 11 September 1999). However, oxygen isotope studies by some geochemists believe in a cold accretion theory where the cloud never reached temperatures in excess of 20 –30 K. The minor impacts of the said primordial material in the collapsing planet cloud created a frictional heat flow that that caused fractionation of the primordial elements into layers of dense and lighter material. This caused the heavier elements such as the irons and nickels to literally sink into the cloud forming the dense metallic core by gravitational attraction. This falling of matter towards the center of mass caused the release of potential energy. The released energy caused the surrounding material to heat up and maintain the molten core. Over time the material would differentiate further forming a distinct crustal and mantle region surrounding the core.
Once the core had solidified tectonic stresses would cause eruptions of magma and gasses on to the surface. This period is known as degassing and during this time the atmosphere would become rich in gasses that had been trapped in the crust. This would create a high CO2 content with small amounts of N2, SO2, H2O and Ar.
The first material to condense would be the refractory elements such as the platinum metals and the oxides of Ca, Al, Ti appearing as solids at around 1600 ° c. Regardless of the method the main accretionary phase was probably finished after 100 million years. Then for 700 million years ago until 3.8 Ga ago there was intense bombardment as the residual planetessimals were pulled towards the larger already solidifying bodies. This is inferred from cratering on the Earth’s moon. Unlike Mercury who was probably impacted vapourising large parts of its silicate material leaving a disproportionately large core and Earth that was possibly impacted to split to form the moon. Venus is not known to have suffered cataclysmic impacts.
After condensation the small planetoids would undergo many stages of small collision and fracturing. Close to the sun where the terrestrial planets were formed, there would be several collisions that might free material. At different distances the actual chemical composition would alter. The mass left after the early condensation might be cleared by the initial instability of the T Tauri type star, but much of it may be left as asteroidal matter. The presence of asteroid orbiting one another has been documented with the discovery of the twins Idra and Dactyl and more recently scientists at the Southwest Research Institute in Colorado have reported the discovery of another moon orbiting an asteroid. Most significantly this discovery was made not by spacecraft flying past the asteroid, but by a ground-based telescope. With a diameter of 210 km, Eugenia is one of the largest asteroids. It was first seen in 1857. Detailed observations of this rock suggest that it rotates every 5.7 hours. Using a large telescope on Mauna Kea in Hawaii, the astronomers noticed a small spec of light close to Eugenia. It was about a hundred times fainter than the asteroid. Observations indicate that the tiny companion is in a near-circular orbit around the asteroid with a period of about 4.7 days. Its orbit is inclined to the line-of-sight by about 45 degrees. (New Scientist March 31 1999)
(Moore 1995)
Geological Constraints on Planetary Class
As we have very few inner planets to study we base much of today's planetary geology on the development of the three main terrestrial planets Venus, Earth and Mars. The inner most planet, Mercury remains poorly and incompletely mapped, due to imaging by the three Mariner 10 flybys alone. The change around the Archaean in the development of earth where the planet's oxygen levels began to deviate from the other worlds is considered crucial to the development of life. Later terrestrialization in the Siluro-Devonian shown in rocks from North America (New York) and England (Shropshire), represent the most significant deviation from other planets and the stabilsation of the atmospheric gases. An atmosphere is the gaseous envelope encompassing a body, planet or large satellite, many more aspects of atmospheres are explored in the atmospheres section below. The term atmosphere is derived from atmos, "vapour" spaira "sphere". Atmospheric exploration began at the close of the nineteenth century. In 1904, L.P. Teisserenc de Bort in France published the results of 581 free balloon ascents. He measured temperature and pressure in the atmosphere height of 14 kilometres. Radio transmitters allowed explorations to 40 km in the next few years. (Brittanica). Since then, high altitude planes and remote sensing data have probed all of our atmosphere and even the atmospheres of the other planets in our solar system. In 1686 Hadley described a single convective cell to describe the motion of energy from the equator to the poles however, this was modified in 1735 by Hadley himself then in 1856 by Ferrel and later in 1941 by Rossby. Their work is summarised in a model known as the tricellular model. The circulation is related to the spin of the Earth and the temperature gradient and this will be explored in the following experiments. (Chamberlin J.W. and Donals M.Hunten 1987).
Whereas the Earth followed the development above towards a stable oxygen rich atmosphere Venus went along a very different path. This is probably due to its inability to shield light elements from the solar radiation. Though the planet has a gravitational field comparable to the Earth, in this case 8.8 ms-1 and therefore unlike smaller planets and planetoids the lighter elements are held in equilibrium by gravity.
The speed at which a gas molecule moves is proportional to (T/M)1/2, where T is absolute temperature and M is molecular mass.
The uppermost layers of the present atmosphere are still very hot and might have been much hotter early in the Earth's history. At temperatures below 2,000 kelvins (K), however, molecules of any compound with a molecular weight greater than about 10 will have an average velocity of less than 11.3 kilometres per second. On this basis, it was long thought that the earliest atmosphere of the Earth must have been a mixture of the primordial gases with molecular weights greater than 10. Hydrogen and helium, with molecular weights of 2 and 4, should have been able to escape. Because hydrogen is the most abundant element in the solar system, it is thought that the most abundant forms of the other volatile elements were their compounds with hydrogen. If so, methane, ammonia, and water vapour, together with the noble gas neon, would have been the most abundant volatiles with molecular weights greater than 10 and, thus, the major constituents of the Earth's primordial atmosphere. The atmospheres of the four giant outer planets (Jupiter, Saturn, Uranus, and Neptune) are rich in such components, as well as in molecular hydrogen and, presumably, helium, which those more massive and colder bodies were apparently able to retain. (Britannica). However, Venus possess a very slow rotational period, that is approximately 243.01 days. This means that the planet was unable to initialise a self perpetuating dynamo effect via the movement of metals in the core, like we observe on Earth. This is what Mariner 2 proved when it failed to detect a magnetic field. As is the case today, when the probe scanned the planet for a magnetic field the planet in the distant past lacked a field as well. This meant that as cosmic rays and supersonic solar winds hit the atmosphere they were not deflected as they are on earth. As the rays hit the atmosphere they were decelerated by the atoms in the upper Exosphere and Mesosphere and in turn the winds ionised these particles. This created a bow shock wave around the planet. The lighter elements such as Hydrogen were stripped of their electron shells and removed from the atmosphere. This left the planet with a hydrogen deficit. Some hydrogen was left in the crust and some that had combined with heavy elements like sulphurs to form the low lying acids remained. However, the free hydrogen was vaporised and therefore the heavier elements such as oxygen recombined with other elements to form molecules such as CO2 and SO2 and various nitrogen compounds.
The lack of hydrogen meant the oxygen did not combine to form water. Without water there were no oceans and no algae’s or bacteria to recycle the carbons or convert them via photosynthesis. Instead the carbon in the atmosphere continued to heat the planet via a greenhouse effect, causing carbon in the rocks to be stripped into the planets atmosphere. At this point short wave radiation from the sun that passed unhindered through the cloud layers struck the floor and was reradiate as longer wave infra-red radiation. This could not pass through the cloud layers and was trapped on the surface. This effect in the early history led to positive feed back of the heat and further increased the greenhouse effect. The presence of CO2 in the atmosphere was first noted by Walter Adams and Theodore Dunham at the Mt. Wilson Observatory. Their spectral analysis showed that there were high concentrations of CO2 however at the time they could not accurately gage how much was present. Current estimates state that the CO2 content is as high as 96% with almost 3.5% N and trace amounts of other gases. In the lower atmosphere sulphuric acid forms, but due to the pressure it does not fall as rain and instead hangs like a sheet of particles in the lower atmosphere. This coupled with the 90 bar atmosphere and 750 Kelvin temperatures makes Venus a very inhospitable planet.
Zimmerman 1995, Gill 1996
Mantle Plumes.
Tectonic activity on the terrestrial worlds is caused by the inability of a planet to radiate its energy from a hot core to space. The planet's cooling cycle causes instabilities in the mantle that drive tectonics. Earth is probably the only planet in the solar system where this is still apparent. Mars having cooled down below this level many millions of years ago. Though the discussion is still taking place, we will assume that the material beneath Venus is still convecting albeit very slowly. The evidence for convection being laid-out above and seems the only way of explaining the Venusian tectonics. There is however very little if any volatile fluid such as water to cause the material to cross the theoretical solidus line and begin melting as shown on the diagram below.
The process of mantle plumes rising is what happens on the Earth and is the reason why hotspots such as those below Hawaii can convect to the surface when the ambient athenospheric temperature is far lower than the temperature required to cause peridertite to melt. On Venus the mechanism suggested for mantle melting is that of decompression melting as opposed to melting via the addition of volatiles. As material moves towards the core the pressure exerted on it increases and so the internal crystal structure is condensed causing internal friction and heating. The material therefore becomes hotter. However the confining pressures are so great that under normal conditions the rock could never melt. That is that, though the rock temperature increases it never does so fast enough to outpace the pressures keeping the rock solid. The interior of Venus, however, is not static and though the viscous waterless mantle means that plume movement is very slow they do occur. This means that the pressure-heated material can be uplifted by other plumes. The specific heat capacity of the dense igneous material is such that even when it is uplifted to areas of lower temperature it retains the high temperatures obtained through the pressure at the lower depths. This means uplifted material crosses the solidus and becomes more plastic and therefore more buoyant. This forms the mantle plumes. Theories suggest these plumes beneath Venus may be as much as 150 – 300 ° c hotter than surrounding athenospheric material.
Gill 1996
Volcanically alone, Venus is very interesting given that it has more volcanoes than any other planet in the solar system. Over 1600 major volcanoes or volcanic features are known, and there are many more smaller volcanoes. Large volcanic edifices on Venus are concentrated primarily in the equatorial regions typically associated with regional topographic rises. The Venus rises have diameters on the order of 1000km similar to terrestrial hotspot diameters and may be related to mantle upwellings beneath Venus’ surface. Most volcanoes exhibit shield style volcanism but the planet exhibits no known long, linear volcano chains and it is argued that there are no clear subduction zones. Most studies suggest volcanism to be regional and much less organised than the discrete Earth regions. Such lavas would not initially suggest the presence of plate tectonics as they are known on Earth but may reflect a combination of several effects. First, due to the high air pressure, Venusian lavas need much higher gas contents than Earth lavas to erupt explosively. Second, the main gas driving lava explosions on Earth is water, which is in very short supply on Venus. The behaviour of gases in the lavas of Venusian eruptions is more geochemistry based than the mapping project proposed but it would be interesting to find work on degassing in high pressure high temperature environments to see how traditionally viscous material behaved
The Magellan data revealed two to three hundred large, round to oval shaped
features with a distinct ring of faults or ridges. The radius of these features
ranged from less than one hundred to greater than one thousand kilometres with
the most common displaying a diameter of two hundred to two hundred and fifty
kilometres. Coronae were first observed on images from the Soviet Venera 15 and
16 probes and the classic model of their formation is derived from Squyres et
al. 1992. These tectono-volcanic features often have a flat, raised or
down-dropped centre and an outer moat-like trough. Lava plains and small shields
are found in both the centres and the moats, and pancake domes are very common
as well. These are the features named coronas and theory holds that they are
formed over small mantle plumes. Rising magmas and heat lift the surface. These
plumes also feed local eruptions, but they are too small for a long string of
eruptions. Thus, the uplifted surface is not fully buried, and a complex mix of
faults and lavas is formed. With later cooling, the uplift then sinks to yield
the down-dropped centres seen in the oldest coronas.
There are superficially similar structures to the above discussed coronas on
Venus. Arachnoid is a designation for a smaller but similar round tectonic
feature. Like coronas, they have a round ring of faults or ridges, other than
the size difference Arachnoids are strictly defined by the presence of external
sets of radial ridges. The rings range from about 50 km to 200 km in size, with
the outer ridges running out another 200 to 400 km. Over 250 arachnoids have
been mapped, and they tend to cluster near both coronas and other arachnoids.
Also, like the coronas, arachnoids are rarely found in the lowest plains.
Instead, most lie just above the lowland plains. Given that Arachnoids look like
coronas and are often form in close proximity and thus are believed to form in
much the same way, which is an important area for our work to concentrate upon. Arachnoids
are smaller than most coronas, however, and they tend to show fewer lava flows
the general explanation being they formed over smaller plumes or small
upwellings off a major mantle plume located elsewhere. However, the lack of lava
flows also suggests that there are more intrusions in arachnoids than in
coronas. Indeed, it has been suggested that the radial ridges may be large
dikes. In this case, these dikes could drain magmas away from the plume and
limit the eruption of lavas at the surface. Arachnoids often lie in faulted
plains, and their outer ridges tend to turn into regional patterns.
For phenomenon that show fewer signs of real volcanism than the coronas or
the arachnoids the term Nova has been assigned. Instead of extrusive volcanism
arachnoids show a pattern of faults and a broad, dome- like uplift. Some of
these faults seem to feed lava flows, but such flows are not common. About 50
Novas have been mapped, with sizes ranging from about 50 km to 300 km. Most are
between 150 and 200 km across, and thus are the same size as many of the
arachnoids. Although rare, novas tend to occur near large volcanoes or near
groups of coronas and arachnoids. They are seldom found alone or in the lowland
plains. Since the higher plains on Venus are thought to lie over mantle plumes,
this suggests that novas are linked to mantle melting in some way. Given their
size and shape, they may mark an early stage of uplift over small mantle plumes.
If this is true, then these novas may turn into arachnoids or coronas in a few
million years. Novas mostly occur next to large shields or major coronae chains.
Thus, they seem to be volcanic. They probably mark an early stage of uplift and
faulting that could later become a corona or a large shield volcano. If they are
the beginnings of coronas or arachnoids then logically it suggests comparatively
recent tectonic activity; their distribution would therefore allow us to
determine the level of heat loss through this form of tectonics today and in the
past. Novas are normally found in long chains and this might represent a form of
micro-tectonics. It is a determination of heat loss that would be of most
importance in a determination of Venusian tectonics.
As well as the tectono-volcanic structures the Venusian plains are modified
by extensive lava flows. The extent of the surface modification by these is
obviously in debate but many cover considerably large areas. The study of these
would allow a challenge to the theory of complete and catastrophic resurfacing
over a geologically short length of time. Mylitta Fluctus is one of the largest
of the flow fields on Venus measuring some 1000 km long by 460 km wide. It lies
on the southern edge of Lavinia Planitia, and drops some 2000 meters from south
to north. Studies show that the flows seem to have formed in 6 separate
eruptions, and most come from a single centre in the Southeast. This source is a
large shield volcano that was formed by the first eruption event. The later
eruptions then produced the longer flows of the main flow field. One interesting
implication that has been pointed out by workers on the data is that this
differs significantly from terrestrial flood basalts where long fissures effuse
lava. Mylitta Fluctus, instead, has a single non-migrating source suggesting
that it may be harder for lavas to reach the surface on Venus. Since the shield
lies on a major rift zone, faulting may have helped these lavas reach the
surface
Venus also demonstrates braided river style flows that meander and have
discernible island structures suggesting the continual flow of lava which
changed their path over time much like Earth’s rivers. There is also a belief
that lavas cut down into previous channels suggesting long term flows in a given
direction perhaps from multiple eruptions or extensive effusion from a single
source. The existence of long time eruptions and resurfacing would assist in the
challenging of the resurfacing paradigm. While Venus has volcanoes of all sizes,
it also shows a range of other volcanic features. The most common are the
lowland plains that cover about 80% of Venus. Looking similar to the lunar mare,
these plains built up from so many large eruptions that few lava flows can now
be seen. The description of these plains as the product of multiple volcanic
eruptions would bring doubt to the theory that Venus was resurfaced in a single
episode.
The structure of the planets has been determined via the study of moment of inertia. Moment of inertia describes the distribution of matter through a body. A homogenous body has a moment of inertia of 0.4 ma2 where m is the total mass and a is the planets radius. Venus’ moment of inertia is near 0.334 suggesting that there is more mass at the centre of the structure. We know from the coronae and gravity anomalies that the mantle is solid but deforms plastically to accommodate mantle upwellings but we are not aware of how deep the mantle is. It is considered to be very similar to the Earth’s having lost none of its silicate material in collisions as was the case with Mercury.
Kasting, J.F.; Eggler, D.H.; Raeburn, S.P,
suggest that the current models of the early atmosphere
consisting mostly of CO2, N2, and H2O,
along with traces of H2 and CO are based on the
assumption that the redox state of the upper mantle has not
changed. This means that volcanic gas composition has remained
approximately constant with time. They argue that this assumption
is probably incorrect. The upper mantle was originally more
reduced than today, although not as reduced as the metal arrest
level, and has become progressively more oxidized as a
consequence of the release of reduced volcanic gases and the
subduction of hydrated, oxidized seafloor. Mantle redox evolution
is intimately linked to the oxidation state of the primitive
atmosphere.
The Physical Processes that Generate Motion in Planetary atmospheres
Atmospheric motions are the products of external forces. Said forces can be created by differential heating due to absorption of solar radiation, gravitational attraction of the sun and moon, or even other planets or celestial bodies, moment transfer or heating from the lower boundary. Atmospheres are also discussed in depth in the section above.
The development of an atmospheric circulation also depends on the rotation, the position of the spin axis relative to the ecliptic the structure and roughness of the lower boundary and the types and concentrations of gases in the atmosphere.
Bolle 1982 stated that an atmosphere could only be motionless with respect to the surface if all molecules are rotating with the same angular speed as the planet. This would effectively establish an equipotential surface. Unfortunately, if perturbations caused a molecule to leave the surface then it would find it would be deposited in an alien environment with differing angular momentums. This would mean the particles speed would be different to the ambient speeds and would begin to create turbulence as other molecules moved in to replace the first particles migration. The Coriolis Effect is greater with geographic latitude and is non-existent at the equator. The Coriolis Effect is responsible for the curving path of the atmosphere. It must be remembered that this is only an apparent force and even published papers refer to the effect as a force; this is strictly speaking incorrect.
The forces on the planet’s atmosphere can vary considerably especially given the range of spin axis inclination values from as low as 3° for Venus to 82.5° for Uranus. There is also the vast difference in rotational speeds from 10 hours for Jupiter to 243 days for Venus. (Bolle 1982)
The tilt of the spin axis on Earth sets up the seasons we observe on Earth. The seasons mean that when a given hemisphere is tilted to the Sun that hemisphere is warmer and therefore the pressure gradient between pole and mid latitude is less. Conversely in the summer the gradient is higher.
Both the atmospheres and oceans have undergone significant secular changes during the history of the Earth, with the atmosphere evolving from an early high CO2-rich, low-oxygen state, to its present day low-CO2, oxygen rich, state. However determining the composition of the early oceans and the major geochemical cycles and their relationship to the Archean atmosphere, are poorly constrained. Given the small amounts of preserved and most importantly unaltered Archean clastic and chemical sedimentary rocks makes the task increasingly difficult. Dawn Y. Sumner extensively studied Archean microbilites publishing papers in 1997.
Previous to this it is theorised that the initial life forms were formed in the ammonia sinks. Sunlight provides the energy required to drive chemical reactions that consume some gases, this is a photochemical reaction. Due to a rapid and efficient photochemical consumption of CH4 and NH3, a methane-ammonia atmosphere, for example, would have a maximum lifetime of about 1,000,000 years. This finding is of interest because it has been suggested that life originated from mixtures of organic compounds synthesized by nonbiological reactions starting from methane and ammonia. Recognition of the short atmospheric lifetimes of these materials poses grave difficulties for such a theory. Water, too, is not stable against sunlight that has not been filtered by overlying layers containing ozone or molecular oxygen, which very strongly absorb much of the Sun's ultraviolet radiation. Water molecules that rise above these layers are degraded to yield, among other products, hydrogen atoms, H. (Britannica)
The influence of microbial communities on the morphology and internal texture of stromatolites has been a hotly debated. Early Soviet workers documented temporal variations in stromatolite morphology and internal textures as representing the evolution of microbial communities through time (summarized in Semikhatov, 1976). In contrast, many western workers considered stromatolite morphology a function of depositional environment rather than the composition of microbial communities (e.g. Cloud, 1942; Logan, et al., 1964). More recently, focus has shifted from stromatolite morphology, which is now generally considered a complex function of both biological and environmental processes (e.g. Ginsburg, 1991; Buick, et al., 1981; Krumbein, 1983), to stromatolite microtextures. Widdel and Schink 1994 found bacteria that could oxidise iron in the absence of oxygen. Purple non-sulphur bacteria were found to form banded iron formations. However, near conclusive proof by Schopf in 1993 and later that oxygen was around from examination of micorbes means Widdel and Schink’s work is no longer required.
The biological processes of photosynthesis an later respiration mediate the carbon cycle and alter the balance of atmospheric gases.
photosynthesis
CO2 + 2H2A >>> CH20 + 2A (or A2) + H20
respiration
In these reactions, CH2O crudely
represents organic material, the biomass of bacteria, plants, or animals; and A
represents the "redox partner" for carbon (reduction + oxidation 
redox), the element from which electrons are taken during the biosynthesis of
organic material and which accepts electrons during respiratory processes. In
the present global environment, oxygen is the most prominent redox partner for
carbon (i.e., A = O in the above equation), but sulfur (S) also
can serve as a redox partner, and modified cycles based on other partners (e.g.,
hydrogen) are possible. Imbalances in the biologic carbon cycle can change the
composition of the atmosphere. For example, if O is the principal redox partner
and if photosynthesis exceeds respiration, the amounts of O2 will
increase. The carbon cycle can in this way serve as a source for O2.
The strength of this source is dependent on the degree of imbalance between
photosynthesis and respiration.
Banded Iron formations occur in Proterozoic rocks, ranging in age from 1.8 to 2.5 billion years old. They are composed of alternating layers of iron-rich material (commonly magnetite) and silica (chert). Each layer is relatively thin, varying in thickness from a millimeter or so up to several centimeters. The banded iron formations are among the most conclusive evidence for the reduced atmospheric Earth. They show that the primitive atmosphere had little or no free oxygen. In addition, Proterozoic rocks exposed at the surface had a high level of iron, which was released at the surface upon weathering. The surficial conditions lacked oxygen so the iron entered the ocean as iron ions. Though the earth was uninhabitated at the time the oceans contained primitive photosynthetic blue/green algae. This life was beginning to proliferate in the near surface waters after 2.5 billion years ago. The algae would produce O2 as a waste product of photosynthesis, the free oxygen would combine with the iron ions to form magnetite (Fe3O4), an iron oxide. This process cleansed the alages environment from the poisonous oxygen, the iron combined in the cherts removing the oxygen and leaving an hospitable carbon environment. The biomass would continue expand unchecked and eventually move beyond the capacity for the available iron to neutralize the waste O2. When this happened the oxygen content of the sea water would rise to toxic levels. The toxic build up would result in large-scale extinction of the algae population, and led to the accumulation of an iron poor layer of silica on the sea floor. As time passed and algae populations re-established themselves, a new iron-rich layer began to accumulate. The biomass would again proliferate beyond the capacity of the iron ions to clean up their waste products, and the cycle would repeat.
It is possible that smaller changes in the atmosphere are related to more cosmic influences. One possible linkage is the sun's influence over the local flux of galactic cosmic rays (GCR). When the solar magnetic field is at its strongest, fewer cosmic rays are able to penetrate to the inner solar system and Earth. And because the GCR are the biggest ionizer of air molecules in the lower atmosphere, they might play a role in processes like cloud formation. Henrik Svensmark, a physicist at the Danish Meteorological Institute, has studied the connection between GCR flux, solar activity, and climate on Earth. He finds that during the past 11-year solar cycle, Earth's cloud cover was more closely correlated with the GCR flux than with other solar activity parameters, such as solar radiance, the main energy emitted by the sun. Svensmark concludes that climate seems to be influenced by solar activity via the GCR- cloud connection. In other words, climate is partly affected by processes in deep space. (Physical Review Letters, 23 November 1998)
More Accurate Methods of Modeling Atmospheres.
In recent years computers have become powerful enough to model almost all the fluctuations in the atmosphere, even if they can not all be processed simultaneously. The largest weather-modelling facility is the European Centre for Medium-Range Weather Forecasting, located at Bracknell. Bracknell received its first computer in 1959 one year after the founding of Control Data Corporation by Seymour Cray. Today the Bracknell Meteorological Office uses a nine million-pound Cray T3E supercomputer with 696 processors. The T3E is currently the fastest Cray computer in production delivering 264 billion floating operations per second. The entire atmosphere is too large even for the T3E and a range of models are used to calculate weather systems but it is possible to construct rather realistic mathematical analogues, or models, of the atmosphere. In the simplest model, conditions at one level only are predicted. (PC Format November 1997).
More realistic descriptions of the atmosphere are possible using a larger number of levels simultaneously, and nine levels are incorporated in the most sophisticated model now being used. (Encarta 1997). This would be the way forwards as the horizontal and vertical gradients in Jupiter’s atmosphere and indeed our own could be modelled more effectively.