Towards the end of the "Expanding Earth Video" topic the subject was raised of whether Mars has also expanded and what could that mean for the possibility of finding evidence of past or present life on Mars. Because many people might be interested in this topic, yet might not have read the previous discussion, I thought it would be good to open a topic on Mars specifically. For those people, I should at least give a few arguments on why some think the Earth has expanded:

(1) It was realized by Hilgenberg, Carey and others that the continents can form a completely interlocking cover over the whole globe if the early radius of the Earth was 50-60 per cent of the present radius. Such perfect matching of continents is unlikely to have arisen by chance. Some proponents of the theory favour slow expansion (since the Earth was formed), others fast expansion (since about 200-300 million years ago) and others a combination of the two.

(2) While evidence for seafloor spreading is definite and measurable, the compensating process of subduction in the plate tectonics theory is largely conjectural. There is no 'smoking gun' of subduction.

(3) The sea floor is in all places not older than 200 million years or so. If sea floors were continually being formed for billions of years, as suggested in the plate tectonics theory, and if older sea floors were to disappear by subduction, one would expect to find here and there relics of older sea floors billions of years old. These have not been found. (This general observation tends to support the fast expansion theory of Carey and others).

(4) If the ocean basins formed relatively late in Earth's evolution through expansion, and if the amount of water on the Earth has stayed roughly constant, then the continents would gradually have become more and more exposed over time as water drained into the ocean basins. Fossil evidence supports this general trend.

(5) The expanding earth theory explains why the continents are very even in thickness. Plate tectonics has no explanation for this.

Many other points were mentioned in the previous thread, both for and against the expanding Earth theory. There is also a vast literature on the subject.

There is some pretty suggestive evidence that Mars like Earth has expanded. For some basic facts on Mars see http://scienceworld.wolfram.com/astronomy/Mars.html
The southern half of Mars is the ancient "highlands" region, raised about 1-4 km above the mean level of the planet. The northern half is the much younger "lowlands". The highlands show much more cratering than the lowlands, which is consistent with the lowlands being relatively newer crust analogous to Earth's ocean crust. Except for the absence of liquid water the configuration is not unlike the continent-ocean pattern of the Earth. There is even a likely spreading centre in the lowlands region in the Tharsis ridge, as well as canyons which could stand in for Earth's ocean trenches. I don't know if there are 'shelves' analogous to the continental shelves on Earth, or if the 'coastlines' fit together on Mars like they do on Earth.

Mars could be an interesting 'lab' to prove the reality of subduction, since the absence of ocean water there makes observations in some ways easier. (Of course, plate tectonics supporters will take the absence of subduction on Mars as evidence that Mars does not have plate tectonics!)

Many recent reports have dealt with evidence of rainfall on early Mars. In the June 6 issue of Science there is a story "Running Water Eroded a Frigid Early Mars" by Richard Kerr, stating that computer simulations of rain falling on Mars' surface seem to produce patterns of runoff similar to what is actually seen. Some additional links on this topic were given at the end of the Expanding Earth Video thread. See also

http://www.collegian.psu.edu/archive...ihealth-03.asp

http://northonline.sccd.ctc.edu/jmasura/earlymars.htm

Could a warm early Mars be connected to Mars expansion? As with the Earth it would be nice to know what caused its expansion. One possible cause of expansion is a secular decrease in G. Suppose that 4 billion years ago the radius of Mars was only 60 per cent of its present value, or 2,038 km. Suppose that G at that time was about 1.4 times the present value. Assuming that there was no increase in the mass of Mars (= 6.4 x 10^23 kg), Mars' surface gravity 4 billion years ago would have been

g = GM/R^2 = 14.4 m/sec^2 .

This is even greater than Earth's present surface gravity of 9.8 m/sec^2.

As discussed earlier, the solar luminosity (SL) would also have been greater if G was greater. A hotter Sun could have made rain on Mars a possibility. The problem is that in Dirac's decreasing G hypothesis, for instance, the increase in SL seems to be too great. Yet this could be offset somewhat if SL were reduced according to present solar models. (These models suggest that the luminosity of the early Sun was 30 per cent less than today, and so the existence of other evidence indicative of a warmer Earth back then leads to the 'faint young Sun paradox')

Finally, it is also reasonable to suppose that Mars at least started off with an atmosphere. If the Earth's atmosphere arose secondarily (e.g., by comets), then Mars would also have received these same gases. Whatever atmosphere Mars had could have easily been retained when Mars was smaller, due to its higher surface gravity . Taken together, the evidence for rainfall on early Mars could be considered as consistent with a decreasing G scenario.

The possibility for life evolving on ancient Mars is then considerably bolstered in decreasing G scenarios, since all the necessary elements would have been there: atmosphere, liquid water, ample sunlight, plus reduced compounds emitted volcanically. Either chemoautotrophic or photoautotrophic models might be entertained. Even in expanding Mars scenarios with expansion occurring at constant G and constant mass, the surface gravity would have been greater at earlier stages and this alone could have been significant for life.

Some of the points I mention were thoroughly debated in the EE Video topic. I raise them again not to antagonize anyone, but merely to introduce the topic to Mars researchers and hopefully to widen the debate.

[(1) It was realized by Hilgenberg, Carey and others that the continents can form a completely interlocking cover over the whole globe if the early radius of the Earth was 50-60 per cent of the present radius]

Umm what does Australia lock into?

2) While evidence for seafloor spreading is definite and measurable, the compensating process of subduction in the plate tectonics theory is largely conjectural. There is no 'smoking gun' of subduction.
]

I'm sure the people of such wonderfull places as New Zealand and Chile would feel safer in their homes, by your rebuttal.

There is no doubt early Mars had an atmosphere. But you can not have you cake and eat it by saying Mars expansion caused the air to thin. Why are we not seeing the same phenomena on Earth. Atmospheric pressure has not changed in the five hundred years since it was first measured.

Your falling sea level argument wont hold water either. In no place on Earth is there evidence of exposed ocean floor. Only shallow sea area, such as central Australia are exposed.

Consenus about Mars is the planet has actually slightly shrunk since formation. With the exception of the Thalis bulge - home of the great volcanoes - most of the major valleys have been created by the planets crust wrinkling as time went on.

Tectonic activity never got started on Mars. Olympus Mons and other sites show this without question.

If all planet expand, why doesn't Venus show signs of expansion? Mercury? Why wouldn't the terrestial planets be the same size, if they are the same age? I'm not sure if Venus is considered one but Mars is a geologically dead planet. There isn't much activity going on what so ever.

You are likely referring to the positions of the continents at the start of the video in the Expanding Earth Video topic. As was discussed in that topic, the positions which appear there are at odds with most representations in the expanding Earth theory (e.g., Vogel, Carey).

I suggest we are seeing the same phenomenon on Earth. However, it may not be that a short period of 500 years would be able to display the effect. In 'fast expansion' models, major expansion did not start until about 200-250 million years ago, and it may have subsequently occurred in phases. These phases may have been linked to the mass extinction events. At the same time, observed seafloor spreading indicates that some expansion is going on now, so we should be able to see a drop in pressure at some point, if our instruments were sharp enough to pick up this tiny effect. In the long run we expanding Earth (EE) models predict global cooling, due to a thinning atmosphere, rather than global warming.

I'm not following you here. What I meant was that the continents were mostly water covered prior to the first major expansion and have been gradually exposed more and more in subsequent expansions. EE does not predict exposed ocean floors.

I suggest this idea is not supported by the evidence discussed at the top.

I think Venus does show it. Most of Venus has been resurfaced with magma, just as most of the Earth has been. The planets need not have started at the same size, and expansion may have been proportional to the initial sizes (at least according to decreasing G theories). Of course the gas planets will not show evidence of expansion in their surface features, even if they have expanded.

The statement that Mars is geologically dead puzzles me. Can we say for sure there is no 'seafloor' spreading along the Tharsis ridge, for instance?

There's a weak magnetic field, indicating that there there is no movement of the piping hot magma in the mantle. I believe this also indicates that the iron core has stopped rotating. Mars is pretty dead, but the thin atmosphere keeps the surface active.

Also, with the "Expanding Earth" theory...

The Earth gains 300 tons of matter per day from meteoroids disintigrating in the atmosphere.

Also, the planets formed through the gathering of matter around stronger gravitational points. The gravity of the planet would shape the form to be spheroid, like the planets are today. Wouldn't Expanding Earth have troubles growing since there is a lot of gravity holding the matter to the center of the sphere?

Umm, no. Most of Earth has not been resurfaced with Magma. Most of the Earth's surface is sedimentary and metamorphic rocks. It is quite unlike the surface of Venus. The recent geologic histories of both planets are very different (hard to say what the early geologic history of Venus was like, as the evidence has been removed).

Yes, we can say that is true. Certainly true today, probably true in the distant past.

The large canyon complex originating near the Tharsus bulge has some curious features, and the origin of it is debated. There was some thought that perhaps it was a failed rift zone. Certainly it is related in some way to the bulge and to the magma plume(s) under the bulge, but exactly how is not determined.

The reason Venus' surface has been resurfaced is due to the atmospheric pressure. The atmosphere is a planet-covering pressure cooker. It heats up the crust until it becomes magma, and then cools down later on. The atmosphere is why Venus is hotter than Mercury.

Could you provide references please? I knew about the 'repaving' of Venus' surface but have not heard of the theory involving the atmosphere heating the crust. Thanks.

I might have been wrong about the atmosphere...

Discovering the Universe, 6th Edition. Comings, N & Kaufmann III, W. 2003

Venus' crust is about 300 km thick (Earth's, by comparison, is 65 km thick).

Incorrect statement on my part about the atmosphere heating up the crust. The radioactive elements heat the insulated crust to the point where it melts, and then the pent-up heat escapes and the process starts again.

Inference on my part that the atmosphere plays a part in it. It's still a pressure cooker, as probes and lander have unfortunately found out.

My bad ops:

No problem. The radioactive/internal heat melting the surface was a theory I was familiar with, I thought the involvement of the atmosphere was a new and recent theory that I hadn't heard about. I'll still see if I can find the book but I'm not hopeful - I don't live in a place with very big libraries.

It's a college textbook. Try a college bookstore. I could also send you a copy of the segment, if you'd like.

Perhaps Mars expanded in the past but the expansion then stopped, at least for now. I have the rough figure that Mars is half "lowlands" and half "highlands". If we equate the lowlands with Earth-like ocean basins and the highlands with continents, then Mars has not expanded to the same relative degree as the Earth has. On Earth the continents now form only 1/4 of the surface, indicating Earth has doubled in radius. The radius of Mars has increased only by a factor of 2^1/2 or 1.41. If so maybe Mars smaller size has something to do with the lesser expansion, or maybe its core.

Okay, I give up. You obviously have no idea what you are talking about, or any real understanding of geology. I better speak to some caver friends of mine, because with all this expansion going on, Jules Verne was right. The centre of the Earth is hollow. Will post photos when we get back.

Funny I used to think Creationist were a little odd....but

I'm a little bit fuzzy on the whole thing, myself. How can the Earth expand unless it creates matter? The amount of matter that collects from spacedust is a tiny fraction of an amount of the Earth's mass.

You suggest that the Earth started expanding after the planets formed and cooled down? How is this mass created? The Earth doesn't have any processes of which I'm aware of that allows it to grow. You'd have to have a hollow planet expand like a balloon. The Earth would have a much lower density is had been expanding than it does now.

It's like Johnny Cochcran and the Wookie defense!

The expanding Earth theory might seem odd, but that's mainly because it is not taught much in high school or university. But I can assure you it is a respectable theory that actually was a forerunner to plate tectonics. There was a period in the 60's where plate tectonics and EE vied for standing. Tuzo Wilson, one of the fathers of plate tectonics, actually supported EE for a while, and wrote on this in Nature. Expanding Earth theories fell by the wayside mostly because there was no clear cause of expansion. Plate tectonics (PT) also had no obvious cause, but because it did call for a change in size of the Earth it just became more acceptable. Scientifically, the evidence still supports EE. It's just not taught in school that way!

Before you discard EE completely, try reading Carey's books "The Expanding Earth" or "Theories of the Earth and Universe". Another good book is Pascual Jordan's "The Expanding Earth". Jordan favoured Dirac's idea that expansion is caused by a secular decrease in the gravitational constant G. There are also a lot of websites on EE now. Just punch in "expanding earth" in Google. The thread Expanding Earth Video also gives a sort of introduction, albeit a somewhat chaotic one.

The possible causes of EE can be briefly summed up as:

(1) expansion due to decreasing G (Dirac theory), which causes planets to elastically rebound and expand.

(2) expansion at constant mass and G, due to some sort of phase change in the core or mantle.

(3) expansion with increase of mass. This was favoured by Carey and some others. The question of course is where did the mass come from?

(4) expansion as a sort of scaled down version of the postulated universal expansion.

The proponents of expansion can't come to an agreement as to what the cause was, and so their case has not gathered much strength. But the absence of a proven mechanism for expansion does not mean that the reality of expansion has been negated. Expansion happened.

The point you made earlier about the thinning of atmospheres on expanding planets reminded me that if Mars was expanding at constant G and constant mass, it might still have been warmer in its early days due to its thicker atmosphere alone. The concentrations of greenhouse gases would have all been greater. It might thus not be critical here to postulate declining G to account for rain on early Mars.

When I mentioned that the Earth has also been resurfaced with magma, I was referring to the new ocean crust formed from basaltic magma extruded along oceanic spreading centres. You are right, though. The Earth has for the most part not been resurfaced, but rather new surface has been added.

My underlying assumption is that planetary expansion can have different forms in different cases. On the Earth it appears to be associated mainly with seafloor spreading, but basalt flooding (e.g., Siberian traps) may also have played a role. On Mars it also seems to have been mostly a process analogous to seafloor spreading. On Venus, it might have occurred through basaltic flooding. As you say, basaltic flooding removes traces of the earlier history, and so we lose some of the possible evidence of expansion on Venus (that we seem to have on Mars and Earth).

Earth has a rift zone that is over 60,000 KM long. Neither Mars nor Venus have anything like that. So, no, Mars has nothing like sea floor spreading.

If you are saying that Earth's rift zone is due to the expansion of the Earth, then you have to explain the lack on other planets. Which you still have not done, except for hand waving at the resurfacing of Venus.

Of course, you also have to explain the subduction zones of Earth, and volcanoes on the subduction zones. Which Earth has, and which Mars lacks. The Martian volcanoes all appear to be associated with plumes, with the exception of some small ones on faults around the Hellas basin, which appear to be associated with the large impact.

On Earth, there are quite distinct types of volcanoes. The rift volcanoes all produce lava that is almost exactly 50% silica. The subduction volcanoes produce lava that is up to 75% (IIRC) silica.

Expanding planets is not an accepted theory because it does not fit with what we observe. For it to displace current accepted theories, it would have to:

1. Explain observations and measurements better than the current theories.
2. Make testable predictions. Cartoons of Earth expanding is not a testable prediction.

Way back in the previous thread I tried to get you to define a prediction that the expanding planet theory makes so we can test it. Do you have one?