I am sure it is the heat trapped in the Earth's interior that made plate movement possible. As the crust cooled, the internal heat could not escape easily and it created the convection cells of the plate tectonics phenomena.

Dear Dr. Yuksel,

In essence, it is the Earth positioning within our solar system that counts. By and large the composition of the various planets is a function of their proximity to our sun. The composition of Earth underwent a differentiation on a larger scale into core, mantle and crust. Crustal plates could only come into existence and motion as this differentiation process has crossed a certain threshold in chemical and physical differentiation when solid and mobile components existed side-by-side or above each other, respectively, and were driven by physical gradients such as heat. Therefore the global tectonics of plate motion becomes more and more obscure going back into the Earth´s history. Will these differentiation processes and the built-up of gradients once upon a time slow down or come to a halt we might not lose our position in the solar system but might take an outward appearance which comes closer to what we know from neighboring planets where these geodynamic phenomena cannot be observed as described from Earth and made by you centerpiece of this thread.

H.G.Dill

The growth rate of the Moon, Mars, Venus, Earth, Neptune, Uranus, Saturn, and Jupiter can be approximated by taking the Base = 1.003 453 602, and raise it to the age of the Individual Planets. That is 1.003 453 602 ^ ( N X 186.6 +66 )

Here are the exponents:

Moon 22 X 186.6 + 66 Million Years

Mars 23 X 186.6 + 66 Million Years

Venus and Earth 24 X 186.6 + 66 Million Years

Neptune and Uranus 26 X 186.6 + 66 Million Years

Saturn and Jupiter 27 X 186.6 + 66 million Years

The results are in meters, so divide by 1,000 to get the radius in Kilometers.

The method generally over estimates the rocky planets, and under estimates the gas giants. Notice 25 is missing. It was probably the asteroid planet before it was obliterated by a collision. Maximum growth occurs when the Solar system passes thru the Crux Arm of the Milky Way Galaxy. The 186.6 is due to the difference in the rotational directions between the MW Galaxy, and the Solar System. The Galaxy rotates in 230 million years, but counter rotation makes us close the gap, and reduce the time of cycles to 186.6 million years. Note Primary extinction events are about 186.6 million years apart.

For your original question, the Earth is just the right size now to show the consequences of that growth in the last 180 million years. Note that Mars is just entering the more rapid growth phase, and the Gas Giants have evolved past the thin atmosphere stages into the increasing atmospheric thickness phases.

If you are Math inclined, raise and lower the Base Number to see how large exponents change the growth rate of planets, especially when they become very big planets.

MWC

I do not completely agree with Harald, with which I often are in concordance. It is not a matter of distance from the Sun. The energy we receive from our star is incredibly high (about 98.000 TW at sea level) much higher than the heat released from the Earth (around 44 TW). The photons of the Sun are essential for the developing of life and mantaining liquid water, but they have no influence on the deep interior dynamics of the Earth.

All the other rocky planets of our system are chemically and mineralogically stratified, with an iron-rich core and silicatic mantle and even lighter crust. Nearly all of them are (or have been) geologically active, with the presence of volcanoes (e.s., Olympus Mons in Mars) and with evidences of faults, rifts and mountain chains. Subsidence is common in the other rocky planets too, but Earth is the only planet charactherized by subduction. The presence of subduction is strictly related to the presence of liquid water, because this compound allowed partial melting of basaltic lithologies at relatively low temperatures, production of granitic s.l. magmas. These evolved melts led to the development of the first continent nuclei. These infant nuclei had (and have) very different rheological behaviour with respect of basaltic oceanic crust, much denster and thinner. However, the presence of liquid water is not sufficient to generate plate tectonics. Indeed, liquid water was present on Mars and Mercury too, but those planets never saw a real plate tectonics.

Worth nothing, subduction is essential for life and for mantaining liquid water on a planet. See what has happened to Mars. On that planet there was liquid water. It reacted with atmospheric CO2 to produce carbonic acid (H2O + CO2 = H2CO3). The dissociation of this acid led to the availability of anionic groups CO3^2-. These reacted with Ca^2+ ions dissolved in Martian water to produce carbonates. In this way, all the atmospheric CO2 was neutralized in the form of carbonates, freezing the planet (whose average temperature is -63 °C).

The CO2 neutralization in the form of carbonates happens to our planet too, but in our case we are lucky because, during subduction, a substantial amount of carbonates is dissociated at mantle depths to CaO and CO2. The vapour phase enters the structure of mantle wedge mineral assemblages and then is transferred to the melt phase, returning in the Earth's atmosphere to re-create the greenhouse effect.

About half of the heat flow of the Earth is related to the presence of radioactive elements 232Th, 40K, 235U and 238U, but these elements are present in the other rocky planets too, so they cannot be considered a peculiarity of the Earth.

In order to have a planet (or a moon) with plate tectonics it is necessary it is geologically active (with a hot core), it has a rigid lid (not too thin nor too thick), a softer (more plastic) mantle beneath the lid, a cold lid denser than hot stuff (i.e., a icy lid does not work), and a sufficiently high Reynolds number. Below I report a statement from Stern et al. (2018, Geosci. Front., 9, 103-119): "stresses associated with mantle convection must exceed the strength of the lithosphere sufficiently to allow plate rupture but not so much stronger that the plate breaks up into drips or so that the bottom of the lithosphere separates from the top of the lithosphere (delaminates; Gerya et al., 2015). These conditions are sufficiently restrictive that plate tectonics currently operates only on Earth, and mantle convection in most terrestrial planets and moons is probably in a stagnant lid regime, where the entire lithosphere of the planet is a single, globe-encircling plate."

What made plate tectonics a dominant process only on Earth?

I do not know how to reply to this question. By sure plate tectonics developed on Earth only.

How did the planet cool down before plate tectonics?

Nobody knows when plate tectonics started, with estimates ranging from 4 to 2 Ga. The Earths started cooling also without plate tectonics. The two concepts (cooling with development of a first peridotitic assemblage, then producing basaltic rocks, and plate tectonics) are not directly related.

Was the Earth's crust formed during the early stages of its evolution or is it the result of a gradual distillation of the mantle that continues today along with crustal recycling?

The first Earth's crust was basaltic and formed as consequence of peridotite partial melting. The first peridotites appeared on Earth's surface few tens to hundreds Myr after its formation, likely during Adean Eon. Then, the density increase led to their sinking in the magma ocean, allowing their partial melting to form the first veneers of basaltic crust, contemporaneously with the formation of the first oceans. In any case the process of continue and irreversible chemical stratification of upper mantle is continuing.

Is the crust still growing or does its recycling compensate for crust formation at mid-ocean ridges and other volcanic areas?

Crust is continuosly growing. Oceanic crust is formed along oceanic ridges and continental crust is formed at subduction settings. Each gram of matter produced along MOR is recycled in a age range from 10 to 250 Myr in subduction zones.

Cheers,

michele

P.S. I invite you to read "A story of the Earth" by Robert Hazen and "Earth: evolution of a habitable world" by Jonathan Lunine.

Earth is the largest of all the terrestrial - Rocky Planets, and it formed just a little Earlier than Venus so it is just a little bigger in Radius, and Mass. Formation and growth can be approximated by the cyclicity of extinction events which is also the cyclicity of planetary growth events. These growth event occur when the Solar system travels through the Crux Arm of the Milky Way Galaxy on a long nearly longitudinal passage thru that arm. The Growth, and extinction events occur on average every 186.6 million years. The Sun, and every planet was " born" or formed for lack of a better term at a whole number interval of 186.6 million years ago, and since the last one was 66.043 million years ago, the ratio is 66.043 / 186.6 = 0.353928188. I am going to round this to 0.354. So every planet, Moon, object, Gas Giant, and Star in our solar system has an age of N X 186.6 + 66 Ma.

What is important here is IF the planets all remained as rocky planets, how big would they be, especially if they did not inflate into Gas Enveloped Planets we call gas giants, or catch on fire, and start burning hydrogen into helium. Note the last five have all undergone volume inflation so their actual radius is far larger than the number I will show here. This evident in their low average density.

Sun : 31.354 X 186.6 = 5850.6564 Ma

1.003 453 602 ^ 5850.6564 = 575,659,736.4 meter radius use 575,660 Km

696,700 / 575,660 = 1.208525866. The Sun only has 20.85 % radial inflation as it is a burning gas ball that is loosing mass . It has been loosing mass for at least the last 2.905 Galactic Rotational Cycles up to the last 3.054 Galactic Rotational Cycles when it got bigger than Jupiter, Ignited, and melted all the Ice that covered the Oceans on Earth. about 625 million years ago. Note that all the larger life forms on Earth have occurred on Earth since the Sun ignited and started warming up the Earth's surface so larger life forms could come up out of the deep oceans, and occupy the land, and later the air.

I will skip 30.354, 29.354, and 28.354 as there are no remaining planets that formed from this galactic rotational time period.

Jupiter, and Saturn : 27.354 X 186.6 = 5104.2564 Ma

1.003 453 602 ^ 5104.2564 = 43,912,072.79 meters radius, use 43,912 Km

Jupiter is actually 69911, and Saturn is actually 58232 km radius. Note that Jupiter got an early growth start time, or started bigger, and Saturn got a latter start time, or it started smaller. If it is start time, Jupiter was about 27,000 years earlier, and Saturn about 27,000 years later. These two have the biggest time spread , they are the oldest pair, the largest pair, the greatest difference in density, and radius so you can only guess that they might have had similar radial inflations at the same time periods. One should be less than 31 % radial gas thickness, and the other more than 31 % radial gas inflation. I put Jupiter at a

rocky planet radius of 48,126 + km radius, and Saturn at a mere 40,089 + km radius. Both as rocky planets only.

Uranus and Neptune are somewhat closer together at 23,428 km, and 22,744 km both as rocky planets only. Uranus is a bit early, and Neptune is a bit late in the formation time of 26.354 X 186.6.

There is no remaining planet for 25.354, but Earth and Venus straddle the cycle at

24.354 X 186.6.

Mars is at 23.354 X 186.6 , and it formed early as it is a little bit too big.

Moon is at 22.354 X 186.6, and it formed late as it is a little bit too small.

You can get the actual planet radius from NASA, and by using 1.003 453 602 ^ age in millions of years, you can get the radius in meters. If you take natural logs of both sides of the equation, you can get the actual age of each planet by solving

N X Ln ( 1.003 454 602 ) = Ln ( Radius in Meters ). N will be a whole number plus or minus 0.1447. N + gives a bigger radius, and a longer age. N - gives a smaller radius ,and a shorter age. At last count there are only just less than 300 Planets and Moons to check to see ( 287 ?? ).

Does any one want to check and compare to see if all of them lie around the

N.354 X 186.6 Ma time sequence cyclicity ?

This might be useful: Chapter Plate Tectonics

if you look for the current understanding regarding the following questions:

• How do the plates move across the surface of a spherical planet?
• Where does the Earth’s surface deform?
• What is the extent of the plates? Do they have a clearly defined base?
• How does plate tectonics operate on human timescales? Can we feel and see plate motions?
• How have the various plates moved across Earth’s surface? When did the Atlantic open up?
• Are the oceanic plates a part of something bigger?
• How do the plates interact with the mantle?
• What drives the plates; what slows them?
• Are there different styles of mantle convection? Is plate tectonics unique?
• How does the plate-mantle system impact our surface environment? What volatiles enter the mantle?
• How and when did plate tectonics start? Did it ever truly “start”?
• How does ocean-plate tectonics remain active? How are new subduction zones formed?
• Is Earth’s tectonic evolution unique?
• How can we communicate better about plates and the mantle?

“Thank you so much for your kind rearrangments and helpful commets. This feedbacks are the best one I've had ever in other sites."

From my recent calculations, there were two planets that were of similar size and mass that tried to occupy the same orbit between Mars and Jupiter. There was a rear end collision, and both planets were partially destroyed, when they were far younger and smaller than they are now. The planets closest to the collision at the asteroid belt benefited the most by being allowed to grow larger. Planets farther away benefited less. I suspect that the Late Heavy Bombardment of planets could have come from this collision.

Any way too calculate the growth rates you need to know the length of 1.0 NET Galactic Rotational Cycle = 186.6 Million years. Every cycle ends in N.354, and the large end of the sequence is 31.354 GRC for the Sun and the age is thus 186.6 X 31.354 = 5850.6564 Ma. The Radius in meters is about 695,700,000 meters.

The Base is 1.003 486 087 . To find a Stars, Planets or Moons Base, you need to know the number of Net Galactic Rotational Cycles, and its Radius in meters.

Take the base raised to the Age to get the Radius. By taking Natural Logs of both sides of the equation, you can solve for the base.

5850.6564 X Ln ( Base ) = Ln ( 695,700,000 ). When you get this ratio you need to raise it to e^x to get a number greater than 1.0.

All of the bases will begin with 1.003 xxx xxx, and all fall within the range of

1.003 545 028 for Jupiter, and 1.003 216 283 for Mimas, with an age of 3798.0564 Ma. This is 20.354 X 186.6.

There are 33 calculations to do. Get your radius from NASA but remember to change to meters from kilometers for the Radius, not the diameter.

First the Star and Planets

31.354 Sun

30.354, 29.354, and 28.354 No Planets.

27.354 Jupiter, and Saturn

26.354 Uranus, and Neptune

25.354 Asteroid 2, and Asteroid 1, destroyed in a collision.

24.354 Earth, and Venus

23.354 Mars and Mercury

Then the Moons

23.354 Ganamede, Titan, Mercury, Calisto

22.354 Io, Luna, Europa, Triton

22.354 Titania, Rhea, Oberon, Iapetus

21.354 Umbriel, Ariel, Dione, Tethys

20.354 Enceladus, Miranda, Mimas

The rest are smaller, and mostly not spherical.

The Exponent is the Age ( elapsed time in Million of years ).

The result is the Radius in METERS from NASA

The base will be between 1.003 486 087 Sun, and 1.003 216 283.

The base for the Sun is less than the Base for Jupiter, and Saturn, but,

the Sun looses a small portion of its mass to energy conversion, so it is lesser in size than if it had not become a fusion reactor.

Note the time to DOUBLE any Radius falls between 199.1788.

million years for the Sun, and 215.8583 million years for Mimas Smaller Planets formed later, and they grow slightly slower than bigger planets that formed and started growing in earlier Net Galactic Rotational Cycles ( GRC's ).

At this point you had better light up and say WHAT ? It is worse than that.

We have less than 120 million years to the next growth spurt. The Goldilocks Zone will move past Earth at or before that time, and, Mars is not ready for Habitation yet. It needs a big E-M field, it needs water, O2, CO2, Nitrogen, rainfall, an atmosphere, and a big Moon, and we have less than 100 million years to make all this happen, and we have to move nearly every species from Earth to Mars.

Oh, and by the way, every species will evolve to be bigger on Mars in its lower gravity, so we might want to leave behind all the ones that are really big now, and have lots of sharp teeth, claws, and a bad attitude. For example when Earth was around Mars size or larger, it had Crocodiles that were 45 feet long, now they only grow to about 19 feet long. Remember Earth is only 186.6 million years ahead of Mars in development, but it now has 1.88 times the radius. Dinosaurs reached their maximum Volume about 176 million years ago. So we might want to take only kit foxes, Margues, and Oscelots with us, and small rabbits. No really big animals.

I am not going to do all the calculations for you. There are only 33 to do.

Those with Computer abilities can whip out all the bases, exponents, radius, and times to double in one to two hours. The bases for time to double are all between 1.85, and 1.903. A base raised to N.354 = 2.0 Use Natural Logs to solve these equations. Ln ( 2.0 ) = 0.693 147 18.

So Plate Tectonics has evolved on Earth as it is the Largest Planet remaining of the original 10, now 8, planets that has not evolved into a Gas Giant YET !

An important concept is that there are very large Rocky Planets Inside all 4 of the Gas Giants making them Large Gas Enveloped Planets. When you change the definition of a planets Radius FROM center to the surface, TO, center to the top of the Atmosphere, the Volume goes way up, but the Density goes way down.

For Jupiter the Radius Ballooned to 131 + %, so the Volume ballooned to 2.48 + times what it would be if we kept the original definition. The trouble is we do not have a sufficiently long enough dip stick to measure the thickness of Jupiter's Atmosphere, and we may never have a good method.

MWC

The Earth has always been growing Crust, at each and every Galactic Rotational Cycle. The Thickest Crust is Under the Continents as it is the oldest Crust, and has has the greatest number of growth cycles of materials deposited on top of it.

The Oceanic Crust is the Thinnest Crust as it is the Youngest Crust, mostly less than 180 million years old, but some smaller areas ( originally equatorial ) were up to 280 million years old. A globe of Mars and a Globe of the Earth side by side will be helpful. They are only 186.6 million years apart, but both have plates, both had deep equatorial canyons, but Mars Continents moved to the South Pole of Mars, while Earth's Continents mostly moved to the North Pole of Earth.

Now here is the thing that most Plate Tectonics Lovers will Hate.

Subduction is an Illusion created by the differential vertical motions of Continental Crust when compared to Oceanic Crust. The material ( basalt ) to feed the growing surface crust must come from somewhere as the Earth grows bigger. It moves out from under the Continents to feed the Earth's Oceanic Crustal Spreading centers ( global spreading rifts ). It was called Isostatic Equilibrium.

I Have renamed it Isodynamic Equilibrium, as it the byproduct of the dynamic movement of liquid, or plastic Basalt from locations of higher vertical pressures to locations of lower vertical pressures. The Bending moment at the edge of continents creates fractures that are prone to release magma as basaltic lava flows, or if mixed with water and gas, explosive by products are produced, with ash, pumice, lahars, pyroclastic flows, etc. In short, the movement of basalt is always trying to reach a vertical pressure equilibrium, but the growth of Earth is always preventing it ever reaching an equilibrium. The result is the Earth will always have Volcanoes, and always have spreading ridges, and basalt will always flow from locations of higher pressure to locations of lower pressure. Note that the Illusion of Subduction occurs only around the biggest Ocean perimeter, and the Indian Ocean. It does not occur around the Atlantic, Africa, or Antarctica. The faster rate of growth of the Pacific Ocean compels the rapid movement of material out from under the perimeter of the Pacific's Continents. In the western North America, the lateral expansion of continents creates the Basin and Range, where fractured strips of land roll over and spread apart thus increasing the surface area of Western Mexico, US, and Canada. A wave passes Eastward under the continents, as the Basalt moves westward out from under the continents. The same wave forms as cars move out from a stopped condition at a traffic light. The wave moves in the opposite direction as the flow of traffic. By volume, the material under the Crust is about 85 % Basaltic, and 15 % lighter Granitic materials. The Lighter Granitic Materials tended to form the Continents first, and the denser Basaltic materials are now forming the floor of the Oceans.

MWC

A reply to Michael Clark:

New and original ideas always are very welcome. I would say that they are essential for a pure and real scientific growth. However I cannot accept sentences saying that "plate tectonics is an illusion". This is particularly true if the sentence is not associated to any quantitative approach, but only generic and unconstrained statements.

It seems that Michael ignores the basic principles of tectonics, structural geology, seismology, tomography, geochemistry, paleontology and igneous/metamorphic petrology.

Mars has no plate tectonics and it has never had it. Earth is the only planet in the Solar system with this characteristic. The plate movement is not equivalent to plate tectonics, a concept that requires subduction as the main process of crustal recycling. As I have already written in my previous comment, subduction is the essential process allowing life to develop and persist, because it recycles back carbon (in the form of carbonates) to be emitted again in the form of CO2 from arc volcanoes.

Earth does not grow bigger. There is no expanding Earth. This is pseudoscience, not science. Michael: do you know how melts are produced beneath oceanic ridges? Do you have idea of the basic principles governing thermodynamics and the styles of approaching to partial melts? Do terms like adiabatic decompression melting sound familiar to you? Do you know what is the influences of volatiles (H2O and CO2, in particular) in modifying the mantle solidi (solidi = plural of solidus, where the solidus is the temperature at which a multi-component system such as the mantle starts melting)? Do you know the differences between absolute temperature and homologous temperature? Do you have any idea of the chemical composition and the differences of magmas emplaced along oceanic ridges, in mid-plate tectonic settings or above subduction systems? Have you ever read anything on isotopic ratios of Sr-Nd-Pb-Hf-Os systems? Do you know what is the ultimate origin of volcanism on the Earth and other rocky planets of the Solar system? Have you ever read any book or scientific article dealing with Adean Earth or the beginning of the Solar system? It seems to me that the reply to all my queries is always "no".

Michael: Researchgate is a scientific community populated by researchers expert in different disciplines. Your approach is rather dogmatic (in the religious sense) and a real scientist cannot interact or even discuss with a person like you. Of course you can continue to believe that subduction is an illusion, but remember that this will remain a personal thought that will never become a scientific truth unless it cannot explain geology in a better way as plate tectonics theory does.

Cheers,

michele

Unfortunately the Math seems to be working out too well for the Cyclical Growth of all the Planets, and the Moons for it not to be true. From the Marie Tharp Map, we know that the age of most of the Ocean Floors is only about 180 million Years.

Taking 0.996 558 284 ^ 180 we get a planet radius of 0.537 763 33907 R

0.537 763 33907 X 6372.4567 = 3426.0 Km when there were no Ocean Basins, and all of the Continents were together on all sides.

To test this you need a 12 inch globe ( Physical is Best ), a 6.5 Inch sphere, a cheese slicer and a block of modeling clay. I think a Number 4 Soccer Ball works well if I remember right. Copy the Continents from the globe and fit them together on the soccer ball. Pick a soccer ball that stays inflated. When you have done this, and you start to think about it............. it will change you view of the world.

Now Mars has a Radius of 3389.5 Km. Using Earth's numbers, the radius at 186.6 million years ago would be 0.996 558 284^ 186.6 = 0.525538449 R.

0.525538449 R X 6372.4567 = 3348.971 Km. Mars is 1.0121 X the Radius that it should be at 3389.5 Km. When I looked at all of the Planets, the 8 that remain,

the closer a planet is to the Asteroid belt, the larger it is when compared to what it ought to be. Jupiter really benefited by the destruction of the planet pair that collided at the asteroid belt as it is 131 % of what it should be. Saturn is 122%, Uranus is close to 110 %, and Neptune is around 106 %. The benefit falls off as the square of the distance from the Asteroid belt collision. The same is true in the Opposite direction. Mars benefited the Most, then Earth, and Moon, then Venus as it is smaller than Earth, and the smallest and farthest away from the collision was Mercury. I actually suspect that Mercury was one of the Collision partners, and the collision slowed its orbital velocity so much that it spiraled into the Sun to establish a new lower orbit. The other Partner, if any of it remained, would have been accelerated to a far higher orbit, or ejected from the Solar System all together. Mercury has an abnormally large core, and an abnormally thin Mantle. This tell me Mercury had a really bad time way back in its past, and suffered a Volume Reducing, slow Velocity Collision with another Very large Object. At a Radius of Only 2440 it is way too small to be a Primary Planet of the same age as Mars at 3389.5 Km. The Ratio is 1.38914 to 1. This ratio should be less than the Earth- Venus Ratio of 1.05275 to 1. Mercury should be around 3260 Km, not 2440 Km. The pair should fairly evenly bracket either side of 3349 plus and minus 2 % or less, But they don't.

Remember this system encompasses 11 Net Galactic Rotational Cycles, and

1 Star, 8 Planets, 2 Destroyed Planets, and 18 large Moons. I have not yet tackled the next groups of smaller younger irregular Moons. There is only around 250 to 260 more to tackle.

I started this process long before the time when things started to click together on March 31, 2000. I started Cave Exploration in 1965, when I was 15, and forced my way into association with University Types, and Physicists. I always wondered why Cave Explorers were dominated by Physicists and University Egg heads.

It all had to do with observations. I never could reconcile my personal observations of the Western US, Mexico, and Canada over the past 55 years with the concepts of Plate Tectonics. So In every System, the processes, the observations, and the explanations must form a complete interlocking network of cause and effects. These must include Insect Sizes, Dinosaur Sizes, Tree Sizes, Planet sizes, Planet Masses, Planet Densities, and Planet Surface Gravity, Thickness of the Atmosphere, Oceans atop continents, Limestone atop Continents, Atmospheric Pressures, temperatures, and Compositions, Elevation of the half pressure, Elevation of freezing at the Equator, and Elevation of freezing at the poles, thickness of the planets oceans, and how they changed with time, etc.

If your Observations and Hypothesis can not encompass, and explain all of the above simultaneously, then it must ,of necessity, not be correct.

Now here is something for you to think about. The flying reptiles with the 40 foot wing spans could not flap their wings, they could not run, they could not launch,

but they had no trouble getting into the air, because they lived in a reduced surface gravity, and a slightly denser surface air pressure, as the air column was taller. When an on shore breeze came toward them after the air warmed up each morning, they just spread their wide leathery wings, and floated up off the ground, and started hunting fish again. At dusk when the wind died, they landed on the beach and walked to a more sheltered place for the Night. They weighed what an average human weighed but were several times the Volume.

MWC

Dear Colleagues:

Frequently, concepts and ideas become so well recognized that they take on the roles of paradigms, and challenging those paradigms can be difficult, even if they are flawed or incorrect in some way. Similarly, misconceptions can take root and become firmly entrenched, albeit rarely in the literature, and again are difficult to dislodge. Both situations are fundamentally unscientific.

Science makes advancement when established theories are shown to be incorrect or at least incomplete. To do that, we must let the data that we collect tell their stories. We should not impose models upon the data, but rather allow the data to yield those models that best represent those features that are necessary to fit the data, an approach often called “Occam’s inversion”. We also should not impose non-physical and unscientific limits on our interpretation models.

At many times, certain ideas or models take hold, and become so strongly held as being correct, that any data or suggestions that those ideas or models may be incorrect or incomplete in some way are dismissed by many. And yet science progresses by making mistakes, and by “proving” theories wrong or incomplete (cf. Popper, 1959; Kuhn, 1962).

The development of the theory of Plate Tectonics is one such example of the battle against strongly held views in opposition to continental drift and plate tectonics. Such strongly held ideas or models are sometimes called paradigms.

On the other hand: we know just a little in our Solar System, one of millions "solar-systems" in the Universe. Also, we know just a little about the Interior "rocket" Planets in our Solar System. Similarly, we know just "a little" about such planets, for instance, Mars. Maybe Mars the best.

On February 14, 1990, following a suggestion by Carl Sagan, the Voyager 1 Mission took a photo of the Earth from about 6.050 million kilometers away. The image inspired Sagan his book 'A Pale Blue Dot'. A new paradigm start.

My idea is try to call your attention that some examples of results that contradicted the prevailing views of the time. Some of those views persist today. Some of these ideas could be characterized as paradigms, such as the interpretation of plate tectonics.

What made plate tectonics a dominant process only on Earth? Are we sure?

Our ideas changes and our paradigm shift far away. Mars is an example.

Mars displays an amazing diversity of tectonic features: fold ridges (thrust faults) and troughs (graben) are abundant, strike-slip faults, also. The Martian tectonic features are concentrated around volcanic provinces and large impact basins. As technology and image resolution improve, smaller and smaller tectonic features can be observed, but the same general patterns are still evident.

After the MGS and following landmark´s missions, we think that it has one-plate but can be separated into three different geological districts: the northern lowlands, the southern highlands, and the Tharsis region. Although ancient seafloor spreading has been proposed as a possible origin for the crustal dichotomy (Sleep, 1994), there is no morphological or chronological evidence for plate tectonics at the dichotomy boundary (e.g., Frey, 2006; Pruis and Tanaka, 1995).

However, there is an interesting magnetic signature in the oldest portions of the southern highlands (Acuña et al., 2001). The alternating bands of strong/weak magnetic fields in the southern highlands are reminiscent of the alternating magnetic bands found in the ocean crust around Earth’s mid-ocean ridges and require that Mars once generated its own active global magnetic field. The location of the magnetic pattern requires that Mars’ dynamo stopped working within a few hundred million years of planetary formation (Acuña et al., 2001; Hartmann and Neukum, 2001), leaving behind no geologic signature of rifting associated with the magnetic stripes.

Our paradigms will surely track away when new missions reach Mars and other planets. May be our Earth is not alone a “Pale Blue Dot” floating in the Universe, maybe we are not alone and privileged to have a planet with Plate Tectonics.

I thank Serdar Yuksel for the original question, and the abundant material of the colleagues that share with us his knowledge and give us a great and new ideas.

Let me share this paper: "Assessment of the cooling capacity of plate tectonics and flood volcanism in the evolution of Earth, Mars and Venus" by van Thienen, Vlaar, and van den Berg in Physics of the Earth and Planetary Interiors 150 (2005) 287–315.

Mario E. Sigismondi