Some Unanswered Questions from the Lunar Rocks

In the previous post I hinted that some of what we found from our study of moon rocks raises issues of self-consistency when viewed in terms of the standard paradigm. To summarize the relevant points of that paradigm, the argument goes that the dust in the accretion disk that was left behind after the star formed accreted into Mars-sized bodies that we shall call embryos, and these moved around in highly elliptical orbits and eventually collided to form planets. While these were all mixed up – simulations suggest what made Earth included bodies from outside Mars’ current orbit, and closer to the star than Mercury’s current orbit. These collisions were extraordinarily violent, and the Earth formed from a cloud of silicate vapours that condensed to a ball of boiling silicates at a little under 3000 degrees C. Metallic iron boils at 2862 degrees C, so it was effectively refluxing, and under these conditions it would extract elements such as tungsten and gold that dissolve in iron and take them with it to the core. About sixty million years after Earth formed, one remaining embryo struck Earth, a huge amount of silicates were sent into space, and the Moon condensed from this. The core of this embryo was supposedly iron, and it migrated into the Earth to join our core, leaving the Moon a ball of silicate vapour that had originated from Earth and condensed from something like 10,000 degrees C. You may now see a minor problem for Earth: if this iron took out all the gold, tungsten, etc, how come we can find it? One possibility is the metals formed chemical compounds. That is unlikely because at those temperatures elements that form only moderate-strength chemical bonds would not survive, and since gold is remarkably unreactive, that explanation won’t work. Another problem is that the Moon has very little water and no nitrogen. This easily explained through their being lost to space from the silicate vapours, but where did the Earth get its volatiles? And if the Moon did condense from such high temperatures, the last silicate to condense would be fayalite, but that was not included in the Apollo rocks, or if it were, nothing was made of that. This alone is not necessarily indicative, though, because fayalite is denser than the other olivines, and if there were liquid silicates for long enough it would presumably sink.

The standard paradigm invokes what is called “the late veneer”; after everything was over, Earth got bombarded with carbonaceous asteroids, which contain water, nitrogen, and some of these otherwise awkward metals. It is now that we enter one of the less endearing aspects of modern science: everything tends to be compartmentalised, and the little sub-disciplines all adhere to the paradigm and add small findings that support their view, even if they do not do so particularly well, and there is a reluctance to look at the overall picture. The net result is that while many of the findings can be made to seemingly provide answers to their isolated problems, there is an overall problem with self-consistency. Further, clues that the fundamental proposition might be wrong are carefully shelved.

The first problem was noted at the beginning of the century: the isotope ratios of metals like osmium from such chondrites are different from our osmium. There are various hand-waving argument to the extent that it could just manage if it were mixed with enough of our mantle, but leaving whether the maths are right aside, nobody seems to have noticed the only reason we are postulating this late veneer is that originally the iron stripped all the osmium from the mantle. You cannot dilute A with B if B is not there. There are a number of other reasons, one of which is the nitrogen of such chondrites has more 15N than our nitrogen. Another is to get the amounts of material here we need a huge amount of carbonaceous asteroids, but they have to come through the ordinary asteroids without perturbing them. That takes some believing.

But there is worse. All the rocks found by the Apollo program have none of the required materials and none of the asteroidal isotope signatures. The argument seems to be, they “bounced off” the Moon. But the Moon also has some fairly ferocious craters, so why did the impactors that caused them not bounce off? Let’s suppose they did bounce off, but they did not bounce off the Earth (because the only reason we argue for this is that we need them, so it is said, to account for our supply of certain metals). Now the isotope ratios of the oxygen atoms on the Moon have a value, and that value is constant over rocks that come from deep within the Moon, thanks to volcanism, and for the rocks from the highlands, so that is a lunar value. How can that be the same as Earth’s if Earth subsequently got heavily bombarded with asteroids that we know have different values? My answer, in my ebook “Planetary Formation and Biogenesis” is simple: there were no embryo impacts in forming Earth therefore the iron vapours did not extract out the heavy elements, and there were no significant number asteroid impacts. Almost everything came here when Earth accreted, and while there have been impacts, they made a trivial contribution to Earth’s supply of matter.

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The Apollo Program – More Memories from Fifty Years Ago.

As most will know, it is fifty years ago since the first Moon landing. I was doing a post-doc in Australia at the time, and instead of doing any work that morning, when the word got around on that fateful day we all downed tools and headed to anyone with a TV set. The Parkes radio telescope had allowed what they received to be live-streamed to Australian TV stations. This was genuine reality TV. Leaving aside the set picture resolution, we were seeing what Houston was seeing, at exactly the same time. There was the Moon, in brilliant grey, and we could watch the terrain get better defined as the lander approached, then at some point it seemed as if the on-board computer crashed. (As computers go, it was primitive. A few years later I purchased a handheld calculator that would leave that computer for dead in processing power.) Anyway, Armstrong took control, and there was real tension amongst the viewers in that room because we all knew if anything else went wrong, those guys would be dead. There was no possible rescue. The ground got closer, Armstrong could not fix on a landing site, the fuel supply was getting lower, then, with little choice because of the fuel, the ground got closer faster, the velocity dropped, and to everyone’s relief the Eagle landed and stayed upright. Armstrong was clearly an excellent pilot with excellent nerves. Fortunately, the lander’s legs did not drop into a hole, and as far as we could tell, Armstrong chose a good site. Light relief somewhat later in the day to watch them bounce around on the lunar surface. (I think they were ordered to take a 4-hour rest. Why they hadn’t rested before trying to land I don’t know. I don’t know about you, but if I had just successfully landed on the Moon, and would be there for not very long, a four-hour rest would not seem desirable.)

In some ways that was one of America’s finest moments. The average person probably has no idea how much difficult engineering went into that, and how everything had to go right. This was followed up by six further successful landings, and the ill-fated Apollo 13, which nevertheless was a triumph in a different way in that despite a near-catastrophic situation, the astronauts returned to Earth.

According to the NASA website, the objectives of the Apollo program were:

• Establishing the technology to meet other national interests in space.
• Achieving preeminence in space for the United States.
• Carrying out a program of scientific exploration of the Moon.
• Developing human capability to work in the lunar environment.

The first two appear to have been met, but obviously there is an element of opinion there. It is debatable that the last one achieved much because there has been no effort to return to the Moon or to use it in any way, although that may well change now. Charles Duke turns 84 this year and he still claims the title of “youngest person to walk on the Moon”.

So how successful was the scientific program? In some ways, remarkably, yet in others there is a surprising reluctance to notice the significance of what was found. The astronauts brought back a large amount of lunar rocks, but there were some difficulties here in that until Apollo 17, the samples were collected by astronauts with no particular geological training. Apollo 17 changed that, but it was still one site, albeit with a remarkably varied geological variety. Of course, they did their best and selected for variety, but we do not know what was overlooked.

Perhaps the most fundamental discovery was that the isotopes from lunar rocks are essentially equivalent to earth rocks, and that means they came from the same place. To put this in context, the ratio of isotopes of oxygen, 16O/17O/18O varies in bodies seemingly according to distance from the star, although this cannot easily be represented as a function. The usual interpretation is that the Moon was formed when a small planet, maybe up to the size of Mars, called Theia crashed into Earth and sent a deluge of matter into space at a temperature well over ten thousand degrees Centigrade, and some of this eventually aggregated into the Moon. Mathematical modelling has some success at showing how this happened, but I for one am far from convinced. One of the big advantages of this scenario is that it shows why the Moon has no significant water, no atmosphere, and never had any, apart from some water and other volatiles frozen in deep craters at the South Pole that almost certainly arrived from comets and condensed there thanks to the cold. As an aside, you will often read that the lunar gravity is too weak to hold air. That is not exactly true; it cannot hold it indefinitely, but if it started with carbon dioxide proportional in mass, or even better in cross-sectional area, to what Earth has, it would still have an atmosphere.

One of the biggest disadvantages of this scenario is where did Theia come from? The models show that if the collision, which happened about 60 million years after the Earth formed, occurred from Theia having a velocity much above the escape velocity from Earth, the Moon cannot form. It gets the escape velocity from falling down the Earth’s gravitational field, but if it started far enough further out that would have permitted Theia to have lasted 60 million years, then its velocity would be increased by falling down the solar gravitational field, and that would be enhanced by the eccentricity of its trajectory (needed to collide). Then there is the question of why are the isotopes the same as on Earth when the models show that most of the Moon came from Theia. There has been one neat alternative: Theia accreted at the Earth-Sun fourth or fifth Lagrange point, which gives it indefinite stability as long as it is small. That Theia might have grown just too big to stay there explains why it took so long and starting at the same radial distance as Earth explains why the isotope ratios are the same.

So why did the missions stop? In part, the cost, but that is not a primary reason because most of the costs were already paid: the rockets had already been manufactured, the infrastructure was there and the astronauts had been trained. In my opinion, it was two-fold. First, the public no longer cared, and second, as far as science was concerned, all the easy stuff had been done. They had brought back rocks, and they had done some other experiments. There was nothing further to do that was original. This program had been a politically inspired race, the race was run, let’s find something more exciting. That eventually led to the shuttle program, which was supposed to be cheap but ended up being hideously expensive. There were also the deep space probes, and they were remarkably successful.

So overall? In my opinion, the Apollo program was an incredible technological program, bearing in mind from where it started. It established the US as firmly the leading scientific and engineering centre on Earth, at least at the time. Also, it got where it did because of a huge budget dedicated to one task. As for the science, more on that later.

The Electric Vehicle as a Solution to the Greenhouse Problem

Further to the discussion on climate change, in New Zealand now the argument is that we must reduce our greenhouse emissions by converting our vehicle fleet to electric vehicles. So, what about the world? Let us look at the details. Currently, there are estimated to be 1.2 billion vehicles on the roads, and by 2035 there will be two billion, assuming current trends continue. However, let us forget about such trends, and look at what it would take to switch 1.2 billion electric vehicles to electric. Obviously, at the price of them, that is not going to happen overnight, but how feasible is this in the long run?

For a scoping analysis, we need numbers, and the following is a “back of the envelope” type analysis. This is designed not to give answers, but at least to visualise the size of the problem. To start, we have to assume a battery size per vehicle, so I am going to assume each vehicle will have an 85 kWh battery assembly. A number of vehicles now have more than this, but equally many have less. However, for initial “back of the envelope” scoping, details are ignored. For the current purposes I shall assume an 85 kWh battery assembly and focus n the batteries.

First, we need a graphite anode, which, from web-provided data will require approximately 40 million t of graphite. Since Turkey alone has reserves of about 90 million t, strictly speaking, graphite is not a problem, although from a chemical point of view, what might be called graphite is not necessarily suitable. However, if there are impurities, they can be cleaned up. So far, not a limiting factor.

Next, each battery assembly will use about 6 kg of lithium, and using the best figures from Tesla, at least 17 kg of cobalt. This does not look too serious until we get to multiplying by 1.2 billion, which gets us to 7.2 million tonne of lithium, and 20.4 million t of cobalt. World production of lithium is 43,000 t/a, while that of cobalt is 110,000 t/a, and most of the cobalt goes to other uses already known. So overnight conversion is not possible. The world reserves of lithium are about 16 million t, so there is enough lithium, although since most of the reserves are not actually in production, presumably due to the difficulty in purifying the materials, we can assume a significant price increase would be required. Worse, the known reserves for cobalt are 7,100,000 so it is not possible to power these vehicles with our current “best battery technology”. There are alternatives, such as manganese based cathode additives, but with current technology they only have about 2/3 the power density and they can only last for about half the number of power cycles, so maybe this is not an answer.

Then comes the problem of how to power these vehicles. Let us suppose they use about ¼ of their energy on high-use days and they recharge for the next day. That requires about 24 billion kWhr of electricity generated that day for this purpose. World electricity production is currently a little over 21,000 TWh, Up to a point, that indicates “no problem”, except that over 1/3 of that came from coal, while gas and oil burning added to coal brought the fossil fuels contribution up to 2/3 of world energy production, and coal burning was the fastest growing contribution to energy demand. Also, of course, this is additional electricity we need. Global energy demand rose by 900 TWh in 2018. (Electricity statistics from the International Energy Agency.) So switching to electric vehicles will increase coal burning, which increases the emission of greenhouse gases, counter to the very problem you are trying to solve. Obviously, electricity supply is not a problem for transport, but it clearly overwhelms transport in contributing to the greenhouse gas problem. Germany closing its nuclear power stations is not a useful contribution to the problem.

It is frequently argued that solar power is the way to collect the necessary transport electricity. According to Wikipedia, the most productive solar power plant is in China’s Tengger desert, which produces 1.547 GW from 43 square kilometers. If we assume that it can operate like this for 6 hrs per day, we have 9.3 Gwh/day. The Earth has plenty of area, however, the 110,000 square km required is a significant fraction. Further, most places do not have such a friendly desert close by. Many have proposed that solar panels of the roof of houses could store power through the day and charge the vehicle at night, but to do that we have just doubled the battery requirements, and these are strained already. The solar panels could feed the grid through the day and charge the vehicles through the night when peak power demand has fallen away, so that would solve part of the problem, but now the solar panels have to make sense in terms of generating electricity for general purposes. Note that if we develop fusion power, which would solve a lot of energy requirements, it is most unlikely a fusion power plant could have its energy output varied too much, which would mean they would have run continuously through the night. At this point, charging electric cars would greatly assist the use of fusion power.

To summarise the use of electricity to power road transport using independent vehicles, there would need to be a significant increase in electricity production, but it is still a modest fraction of what we already generate. The reason it is so significant to New Zealand is that much of New Zealand electricity is renewable anyway, thanks to the heavy investment in hydropower. Unfortunately, that does not count because it was all installed prior to 1990. Those who turned off coal plants to switch to gas that had suddenly became available around 1990 did well out of these protocols, while those who had to resort to thermal because the hydro was fully utilised did not. However, in general the real greenhouse problem lies with the much bigger thermal power station emissions, especially the coal-fired stations. The limits to growth of electric vehicles currently lie with battery technology, and for electric vehicles to make more than a modest contribution to the transport problems, we need a fundamentally different form of battery or fuel cell. However, to power them, we need to develop far more productive electricity generation that does emit greenhouse gases.

Finally, I have yet to mention the contribution of biofuels. I shall do that later, but if you want a deeper perspective than in my blogs, my ebook “Biofuels” is 99c this week at Smashwords, in all formats. (https://www.smashwords.com/books/view/454344.)  Three other fictional ebooks are also on discount. (Go to https://www.smashwords.com/profile/view/IanMiller)

Climate Change and the Oceans

It appears that people are finally seeing that climate change is real, although the depth of their realization leaves much to be desired. Thus German politicians are going to close down their nuclear reactors and presumably burn more carbon. Not exactly constructive. A number of US politicians simply deny it, as if to say that if you deny it often enough, it will go away. Here in New Zealand we have politicians who say, yes it is real, but what they are doing about it tends to be to encourage electric vehicles and bicycles, with a bit of tree planting. Good intentions, but perhaps the commitment is a little less than necessary, but still better than the heads in sand approach. So, consider the size of the problem: the Intergovernmental Panel on Climate Change has stated that to limit global warming to 1.5 degrees compared with pre-industrial levels could require the removal of 20 billion tonnes of CO2 from the atmosphere each year until 2100. That is a much bigger than average ask. However, planting trees is a start, and the good news is they keep working at it, year after year. So, what to do? In my opinion, there is no one big fix. The concept of beating climate change with a thousand cuts is more appropriate. Part of the problem is to persuade people to do something. They turn around and say, why me? Who pays?

As an example, it has been argued that in the US the application of biochar to soils could improve grain harvests by 4.87 – 6.4 %. The carbon tends to last for maybe hundreds of years, at least to some extent, so the argument goes that it will eventually pay for itself, but initially it is a cost. This works particularly well in acidic heavily weathered soils, where the yields are generally somewhat low because they do not hold nutrients well. This is also not exactly a single bullet solution, since with good uptake, it would sequester and offset about 0.5% of US emissions.

There was an article in a recent edition of Nature that summarised marine geoengineering. Rather pickily, they stated that none of the proposals have been rigorously tested scientifically nor published in peer-reviewed journals. Part of this gripe is fair: they complain that results have been published, but in places like websites that no longer work. That is a separate issue really, and provided the work is properly done, peer-reviewed journals, following editorial contractions to save space, may not be the best. But let us leave that for the moment. The oceans are an attractive place for one reason: they are not doing much else other than being a place for fish to live in. Land tends to be owned, and much is either required for environmental reserves or food production. Certainly, there is a lot of land that is little better than waste, often left over from previous forest harvesting, and there is no reason why this could not be planted. Another useful contribution, but what are the options for the sea?

The first approach noted by Nature is to try to reduce the albedo, by reflecting incoming sunlight. Two ways proposed for doing this would be to put films on the water, or to spray water upwards and let it form clouds. The latter should be reasonably harmless, leaving aside the problem of whether some places might be adversely affected, a problem that applies to any such proposal. The former could have a serious adverse effect on marine life. Squirting water into the air to form clouds would seem to reasonably easily tested, but it also leaves the question, who is going to do it because ultimately this concept involves a cost for which there is no return.

Two more processes noted in the article are the spreading of alkaline rock into the sea to absorb CO2, and the spreading of iron-rich fertiliser to promote the growth of microalgae. The problem for the first is what sort of rock? A billion tonne of burnt lime per year would do, but first it would have to have its CO2 pyrolysed off, so that would emit as much as it saved. We could try basalt, such as peridotite, but if we powdered that it would make more sense to apply it to land where previously we had applied lime because it does much the same job, but also absorbs carbon dioxide. The iron fertiliser case is more interesting. There have been experiments to do this. An example: a ship sailed around, spread the crushed rock, and found that yes, there was a microalgal bloom. However, they also concluded that the amount of carbon that was fixed by sinking to the bottom of the sea was insufficient to justify the exercise. That, however, omits two other thoughts. First, what happened to the algae? If it was eaten by fish (or mammals) that would increase the food supply, and an increase in animal biomass also fixes carbon. The second thought is that if it were harvested, it could well be used to make biofuels, which would reduce the requirement for oil consumption, so that is equally useful. Can it be harvested? That is a question that needs more research. As a general rule, if there is just one thing that needs doing, there is usually a way, if you can find it. The making of fuel is easy. I have done it. There is, of course, the problem of making money from it, and with the current cost of oil that is impossible. Also, scale-up is still a problem to be solved.

The final two proposals were to cultivate macroalgae and to upwell deep water and cool the top. The latter does nothing for the carbon problem, so I shall not think too hard about that, but it is almost essential for the former. In the 1970s the US Navy carried out experiments on growing macroalgae on rafts in deep water, and they only grew when deep water was brought to the surface to act as a fertiliser. These algae can also be used as fuel, or the carbon absorbed somewhere else, and some algae are the fastest growing plants on Earth. It is quite fascinating to watch through a microscope and see continual cell division. This may be easier than some think. Apparently floating Sargassum is filling up some sections of the Atlantic and off the coast of Mexico.

So the question then is, should any of this be done? The macroalgae probably have the lowest probability of undesired side effects, since it is merely farming on water that is otherwise unused. However, to absorb enough carbon dioxide to make a serious difference an awful lot of algae would have to be grown. However, the major oceans have plenty of area.

Ebook Discount.

Through the month of July, my ebooks at Smashwords will be discounted. The fictional ebooks include”

Puppeteer:  A technothriller where governance is breaking down due to government debt, and where a terrorist attack threatens to kill tens to hundreds of millions of people and destroy billions of dollars worth of infrastructure.

http://www.smashwords.com/books/view/69696

‘Bot War:  A technothriller, set about 8 years later, a more concerted series of terrorist attacks made by stolen drones lead to partial governance breaking down.

Smashwords    https://www.smashwords.com/books/view/677836

Troubles. Dystopian, set about 10 years later still, the world is emerging from anarchy, and there is a scramble to control the assets. Some are just plain greedy, some think corporate efficiency should rule, some think the individual should have the right to thrive, some think democracy should prevail as long as they can rig it, while the gun is the final arbiter.

https://www.smashwords.com/books/view/174203

 

Earth’s Twin: Venus

Leaving aside the Moon and the Sun, Venus is the brightest object in the sky, and at times the closest. Further, Venus is the only planet that is comparable to Earth; its mass is about 81.5%, its size is about 95%, and its gravity is about 90.5% that of Earth. The orbit of Venus has only 1/3 of Earth’s eccentricity, and while Earth has an axial tilt of 23.5 degrees (which results in right now I am embedded in winter and many of the readers will be enjoying a pleasant summer, or maybe a heat wave) Venus has a tilt of only 2.6 degrees. That means that Venus has a more or less uniform temperature and no seasons. At first sight, that would make it an attractive target for space probes, but while NASA has sent eleven orbiters and eight landers to Mars, it has only sent two orbiters to Venus. Why the lack? Not for lack of interest since from 1990 NASA has considered nearly thirty proposals, but it approved none. The dead hand of the committee strikes again. The reason is that Venus, up close, is strangely unattractive.

The first problem is atmospheric pressure, which is about 90 bar over most of the planet, and it has an average surface temperature of about 460 degrees C but this can vary by +160 degrees C. The second problem is the nature of the atmosphere. Most of it is carbon dioxide. Venus also has about four times the amount of nitrogen than Earth has, and all of that is relatively harmless. What is less harmless is the atmosphere has clouds of sulphuric acid, together with hydrogen chloride and hydrogen fluoride. Hydrogen fluoride is particularly nasty, because it reacts with glass, and while the sulphuric acid will attack all the basic electronics, etc, the hydrogen fluoride will attack lenses. Very shortly, photography, or seeing where a rover is going, will no longer be possible. And, of course, if it can survive, the heat soon kills it. The first lander to return data was Venera 7, a 1970 Soviet lander that survived for 23 minutes. In 1975, Venera 9 sent back the first pictures from the surface, but it too did not last very long. Funding committees do not encourage very expensive rovers with a very short life.

This may change. NASA is designing a “station” that should last at least sixty days, and operate at the ambient temperature. The electronics would be made of silicon carbide, a substance that conducts electricity and melts somewhere above 2,800 degrees C. No danger of that melting, although all the metals in the craft would have to be resistant to the ambient heat and the corrosion. Titanium would probably manage reasonably well. So maybe we shall get to know more about the planet.

There have apparently been proposals to “colonise” Venus through “settlements” floating above the cloud levels, i.e.presumably some ship-like structure supported by gigantic balloons. Personally, I feel this is unreal. The total weight must displace an equal weight of gas, and the idea is to get above the clouds. Up there, the gas is nowhere near as dense (the pressure is only about half that 90 bar at the top of the highest mountain) and to go higher the pressure really drops away. So to support sufficient mass you would need very large balloons, made of what? Any fabric or rubber would be broken down by the solar UV at that height. Metals would corrode. And what would the gas be? The obvious ones would be hydrogen and helium (no danger of fire because there is no air) but these gases leak like crazy. You may think you can hold it, but for centuries? Then there is another minor problem: at the top of the atmosphere winds can reach several hundred kilometres per hour.

So what is “wrong” with Venus, from our point of view? There are two things. The first is the very slow rotation, which happens to be retrograde. The direction is not so much a problem, but the slowness is. However, the main one is, no significant water. If Venus had the amount of water Earth has, it would have fixed all that carbon dioxide as limestone or dolomite, in which case the atmospheric pressure would be about 3 times our atmosphere (because it has four times the amount of nitrogen). If we wanted to have breathable air, we would have to add another atmosphere of oxygen.

So in theory we could terraform Venus. At the expense of much energy what we would have to do is bring in a number of Kuiper Belt objects, or maybe cometary material from around Jupiter would be better because they contain much less additional nitrogen and carbon monoxide, and make them hit Venus, preferably on the side in a way that the angular momentum of the incoming object was added to the current Venusian rotation, in other words, spin it up. Give it water, and chemistry would do the rest, although it would probably also be preferable to cool it by shading it from the sun at least to some extent. Yes, the temperatures would still be high, but as long as it can cool to 300 degrees C, the pressure will ensure there is some liquid, and the fixing of the gas will start, and initiate positive feedback

Suppose we could give Venus as much water as Earth, then the planet would be more like a water world. It is an interesting question whether Venus has any felsic/granitic material. This is the stuff that makes continents. The great bulk of the material on any rocky planet is basaltic, which in turn is because the oxides of silicon, magnesium and iron are the most commonly available rock-forming materials. Aluminium, as an element, is over an order of magnitude less common than silicon, which it replaces in aluminosilicates. Being less dense than basalt, granite floats on the basalt, provided it can separate itself from the basalt. In my ebook “Planetary Formation and Biogenesis”, I propose that the separation essentially has to take place prior to and during planetary formation. Venus does have two minicontinents: Ishtar and Aphrodite Terrae.

The actual differentiation of the planet, when the granite moves from the deep and comes out on the surface occurs slowly (the small amounts of plagioclase on Mars apparently took about two billion years.) and the rate probably depends on the amount actually accreted. The evidence is that on Earth very large amounts erupted in massive pulses. In the absence of such granite, a large planet will be rather flat, apart from some volcanic peaks.

There would still be a problem in that Venus has no plate tectonics. They are needed to provide the recycling of carbon dioxide, as eventually if the lot were fixed, any life would presumably die. We don’t know what starts plate tectonics. One possibility is the presence of granitic continents, another is the forces arising from rotational motion.  It is just possible they could start if there were more rotational motion, but we don’t know. All in all, not an attractive planet in detail, so maybe we should look after our own better.