Thread: Life on a planet with missing heavier elements

I’m neither a biologist nor a biochemist but I’m guessing that Iodine is the highest atomic number element that a human being needs in his or her diet to stay healthy. Now let us say that we have decided to settle and start afresh on an earthlike planet where there were no elements above iodine. Could we exist, function and colonise such a planet (assuming that it had a similar atmosphere , surface temperature, blah, blah etc. to Earth). Could we grow crops, build houses and educate our children?
There would be no lead, gadolinium, gold and so on and probably no atomic age would ever occur in our history, but could humans survive, perpetuate and maybe even develop mathematics and technology?
How would life differ from Earth? I’m no expert on stellar nucleosynthesis and have not researched to see if iodine is a valid final-step, but if it is, would it be enough for us? If it isn’t, what atomic number element would we have to go up to?

hey man great post really made me think.

If we were on a planet with just the base elements that we required to live then yes i imagine we could live but the amount we could advance is interesting.

Mathematics i think would develop regardless of technology, in fact if we ever contacted another alien civilization mathematics would probably the first way we communicate, a stoty which i find amusing is that above plato's academy are the words "enter here only those who understand geometry". sidenote-cant remember the exact quote. which is basically saying that things like pythagoras's theorem would hold in all universes and stuff.

Technology would develop to a point but would we be limited by the available elements? perhaps we would devote more research to the few available elements and discover incredible properties under different conditions.

The potential for developement is really a function of too many variables but it is an interesting thought experiment

Originally Posted by organic god

hey man great post really made me think.

If we were on a planet with just the base elements that we required to live then yes i imagine we could live but the amount we could advance is interesting.

Mathematics i think would develop regardless of technology, in fact if we ever contacted another alien civilization mathematics would probably the first way we communicate, a stoty which i find amusing is that above plato's academy are the words "enter here only those who understand geometry". sidenote-cant remember the exact quote. which is basically saying that things like pythagoras's theorem would hold in all universes and stuff.

Technology would develop to a point but would we be limited by the available elements? perhaps we would devote more research to the few available elements and discover incredible properties under different conditions.

The potential for developement is really a function of too many variables but it is an interesting thought experiment

I like your answer and this is the sort of thing that I am looking for. I guess that with fewer elements we would spend more time on developing our knowledge of the 53 that we had rather than the full 92 that we don't have, but assuming we arrived in a spaceship (and didn't evolve on this new planet) therefore we already had knowledge of uranium etc. but decided we could forgo the heavier elements, could we actually survive or would we find that we needed some more? Is iodine enough or would we start to die of some dreadful enzyme failure?
If we did survive, would we be stuck in some technological dead-end? Could we still develop TV camera technology without europium?
We would have no pretty bismuth crystals but is there any way without thorium or uranium that we could synthesise other elements? Should we have brought small amounts of other higher elements with us when we first arrived to settle? Do we really need these other elements and can we find other ways to advance technology without them?
Am I missing the point somewhere and is iodine a bad choice for the upper elemental limit for my question?

Another interesting point, human ingeniuety is something that is difficult to measure, if a procedure/product can be done easily with component X, is there an incentive to investigate alternative methods without component X.

but let us say that component X does not exist. suddenly we must try to develop new methods, new ideas. it is my belief that this is how research could be conducted. isolate the key element or component whatever it may be. then say "how can we do this without X"

another interesting thought would be that there exists some planet out there with more than than the elements we have discovered and put in the periodic table, perhaps these elements are incredibly useful and make processes we consider diffuclt incredibly simple due to there properties. it is like adding a group to the table which really blows my mind

Originally Posted by organic god

Another interesting point, human ingeniuety is something that is difficult to measure, if a procedure/product can be done easily with component X, is there an incentive to investigate alternative methods without component X.

but let us say that component X does not exist. suddenly we must try to develop new methods, new ideas. it is my belief that this is how research could be conducted. isolate the key element or component whatever it may be. then say "how can we do this without X"

another interesting thought would be that there exists some planet out there with more than than the elements we have discovered and put in the periodic table, perhaps these elements are incredibly useful and make processes we consider diffuclt incredibly simple due to there properties. it is like adding a group to the table which really blows my mind

That's also interesting but I don't wish to fly in the face of science; any other higher elements that we haven't discovered yet would probably be highly unstable with impossibly short half-lives to be of any use, even if we do reach the so-called island of stability, so a planet with such elements probably would not be earthlike and fit for humans to live on.
What you said earlier though about component x is quite interesting. It's probably down to economics.
Let's say for example that my new planet is incredibly rich in Scandium (an element that I feel is so often overlooked), then maybe more research would be done into this element and more uses would be found for it. I think that we know more about the chemistry of the elements that are cheaper to work with. If element x didn't exist then we may not bother to find it, but if element x was plentiful then we would be using it in the household, industry, commerce and all sorts of things.

yes perhaps element x is plentiful and therefore researching it would be important.

however what if we had element y, element y is not particularly plentiful but it is incredibly useful and has widespread application, sure it is expensive to produce, but perhaps research money would be better spent on component y.

incidentally why do you think scanadium is overlooked?

Originally Posted by organic god

yes perhaps element x is plentiful and therefore researching it would be important.

however what if we had element y, element y is not particularly plentiful but it is incredibly useful and has widespread application, sure it is expensive to produce, but perhaps research money would be better spent on component y.

incidentally why do you think scanadium is overlooked?

I'm an old chemist who dropped out for twenty years and is just returning to it.
In my day Scandium was the 'forgotten one'. It had little use and was just the 'name' that came between Calcium and Titanium. Nowadays they're finding all sorts of uses for it. Same with Thulium... "what is this stuff??", they would ask.... nobody was curious enough, nobody cared, but science doesn't progress without curiosity....

I would like to point out that a planet with no elements of higher atomic number would not have a hot core, due to very much decreased rate of nuclear decay in the core/mantle of said planet. As a result, the temperature difference between day and night would be much larger, as heat would be lost into the ground from the atmosphere. This would kill us.

Earth has a thermal gradient of around 25-30 degrees celcius per kilometer in the crust, so the atmosphere takes much longer to cool down at night.

Originally Posted by drowsy turtle

I would like to point out that a planet with no elements of higher atomic number would not have a hot core, due to very much decreased rate of nuclear decay in the core/mantle of said planet. As a result, the temperature difference between day and night would be much larger, as heat would be lost into the ground from the atmosphere. This would kill us.

Earth has a thermal gradient of around 25-30 degrees celcius per kilometer in the crust, so the atmosphere takes much longer to cool down at night.

Thanks for that. I guess we need to go up to thorium or uranium then.

Originally Posted by drowsy turtle

Earth has a thermal gradient of around 25-30 degrees celcius per kilometer in the crust, so the atmosphere takes much longer to cool down at night.

This is simply incorrect. (your conclusions, not your temperature gradients.) The total heat flow from the interior of the Earth over a period of one year would melt less than a 1cm thick layer of ice.

One of the main factors maintaining a reasonably equable night temperature is the absorption of heat by water in the surface layers of the soil.

Further to the main point. I presume this was posited as an intellectual exercise only. There is no mechanism by which a planet could be left devoid of the heavier elements - unless a century plus of geochemistry has been completely wrong.

So, as an intellectual exercise, without the radioactive elements no molten core - so no magnetic field; no mantle convection - so no plate tectonics; no plate tectonics - so no continents after a while.

You could always make small quantities of the heavier elements artificially if you really needed them for something.

Originally Posted by John Galt

Originally Posted by drowsy turtle

Earth has a thermal gradient of around 25-30 degrees celcius per kilometer in the crust, so the atmosphere takes much longer to cool down at night.

This is simply incorrect. (your conclusions, not your temperature gradients.) The total heat flow from the interior of the Earth over a period of one year would melt less than a 1cm thick layer of ice.

I said nothing about heat flow. I said about thermal gradient; they are not the same thing.

I said that for every kilometre you go towards the centre of the Earth, the temperature increases by around 25-30 degrees celcius. For the lithosphere, at least. I suggest you read my signature.

Originally Posted by John Galt

One of the main factors maintaining a reasonably equable night temperature is the absorption of heat by water in the surface layers of the soil.

I don't have my calculations handy, but I once showed that the energy needed to warm the entire atmosphere by 1 degree is about the same as that needed to warm the whole of the world's water by about 0.3 degrees. So, by your logic, there would have to be more water than there exists on the whole of the earth trapped in the top layers of soil just for this to have a significant effect on the whole atmosphere. This is not including the oceans.

Originally Posted by John Galt

Further to the main point. I presume this was posited as an intellectual exercise only. There is no mechanism by which a planet could be left devoid of the heavier elements - unless a century plus of geochemistry has been completely wrong.

It could all have decayed, or the planet could form in a low orbit around its star so almost all heavy material would fall into the star. Just off the top of my head, not necessarily a serious suggestion.

Originally Posted by John Galt

So, as an intellectual exercise, without the radioactive elements no molten core - so no magnetic field; no mantle convection - so no plate tectonics; no plate tectonics - so no continents after a while.

This in itself is not important. The moon,Venus, Mars and Pluto, and probably others in the solar system, have no plate tectonics.

Also, mantle convection has not been proven to cause plate movement (I heard that one of Earth's plates is moving against the convection below it).

Originally Posted by drowsy turtle

Originally Posted by John Galt

Originally Posted by drowsy turtle

Earth has a thermal gradient of around 25-30 degrees celcius per kilometer in the crust, so the atmosphere takes much longer to cool down at night.

This is simply incorrect. (your conclusions, not your temperature gradients.) The total heat flow from the interior of the Earth over a period of one year would melt less than a 1cm thick layer of ice.

I said nothing about heat flow. I said about thermal gradient; they are not the same thing.

And thermal gradient has nothing to do with maintaining an equable nocturnal temperature at the surface of the Earth.
1. I am not and did not dispute the figures you quoted for thermal gradient.
2. The relevant issue is how much of this internal heat from the Earth is available to mitigate the fall in temperature that follows sunset.
3. The fact is that this heat flow is wholly inadequate to have any significant effect at all.
4. Average heat flow from internally derived heat is around 0.075 watts/square metre.
5. Average heat flow from solar insolation is around 250 watts/square metre.
6. Thus there is a difference of more than three orders of magnitude between the solar heating and heating due to the heat flow from the interior. The latter is a mere .03% of the former.

Originally Posted by drowsy turtle

I don't have my calculations handy, but I once showed that the energy needed to warm the entire atmosphere by 1 degree is about the same as that needed to warm the whole of the world's water by about 0.3 degrees. So, by your logic, there would have to be more water than there exists on the whole of the earth trapped in the top layers of soil just for this to have a significant effect on the whole atmosphere. This is not including the oceans.

Water is a heat sink. We appear to agree on that. Coastal areas are famed for their mild temperatures at night - lots of water. Deserts are famed for their very cold nights - not much water here. Apart from that I have no idea what you are trying to say.

Originally Posted by drowsy turtle

Originally Posted by John Galt

Further to the main point. I presume this was posited as an intellectual exercise only. There is no mechanism by which a planet could be left devoid of the heavier elements - unless a century plus of geochemistry has been completely wrong.

It could all have decayed, or the planet could form in a low orbit around its star so almost all heavy material would fall into the star. Just off the top of my head, not necessarily a serious suggestion.

I'm glad it's not a serious suggestion. It won't work. It fails on the grounds of nuclear chemistry, phsyics and geochemistry.
1. Since the majority of elements beyond iodine have perfectly stable isotopes there is no way in which they could have all decayed.
2. Heavy material does not just fall into the parent star. Conservation of angular momentum ensures that - in simplistic terms - material keeps on orbiting. Now if we want to make it more complex and take into account accretionary dynamics, disc turbidity, opacity and viscosity, thermal gradients and resultant condensation sequences, etc, then guess what - the heavy stuff still won't fall into the star any more than the light stuf.
3. And one of the main reasons is that the elements are not there as pure elements, but are combined with each other. Take a look at some analyses of chondrites and explain how you are going to eliminate the elements heavier than iodine. It can't be done.

Originally Posted by drowsy turtle

Originally Posted by John Galt

Further to the main point. I presume this was posited as an intellectual exercise only. There is no mechanism by which a planet could be left devoid of the heavier elements - unless a century plus of geochemistry has been completely wrong.

It could all have decayed, or the planet could form in a low orbit around its star so almost all heavy material would fall into the star. Just off the top of my head, not necessarily a serious suggestion.

Originally Posted by John Galt

So, as an intellectual exercise, without the radioactive elements no molten core - so no magnetic field; no mantle convection - so no plate tectonics; no plate tectonics - so no continents after a while.

This in itself is not important. The moon,Venus, Mars and Pluto, and probably others in the solar system, have no plate tectonics.

Are you sure? Plate tectonics (in the conventional sense) is probably absent from Venus and Mars. It's presence on the Earth may well be responsible for persistence of life on this planet. That would seem to make it somewhat important.

Originally Posted by John Galt

Also, mantle convection has not been proven to cause plate movement (I heard that one of Earth's plates is moving against the convection below it).

Nothing in science is ever proven - yadi, yadi yaddah. The consensus opinion of the vast majority of experts is that convection is a vital part of plate tectonics.
We would fully expect to see an instance or two where plate motion was opposite to that of the probable convection flow. Indeed I would see this as supportive evidence for the concept. We know that subduction zones can and have reversed direction in the past. It is good news if we actually have evidence of the process caught in mid-stream. Perhaps you can provide a citation. I should like to read more.

Originally Posted by John Galt

Also, mantle convection has not been proven to cause plate movement (I heard that one of Earth's plates is moving against the convection below it).Nothing in science is ever proven - yadi, yadi yaddah. The consensus opinion of the vast majority of experts is that convection is a vital part of plate tectonics.
We would fully expect to see an instance or two where plate motion was opposite to that of the probable convection flow. Indeed I would see this as supportive evidence for the concept. We know that subduction zones can and have reversed direction in the past. It is good news if we actually have evidence of the process caught in mid-stream. Perhaps you can provide a citation. I should like to read more.

There are a number of competing mechanisms for sea-floor spreading. None have much evidence suporting them, but convection is the most widely accepted.

Personally, I don't think it is a satisfactory explanation.

As I said, I heard it somewhere about the reversed convection. I'm afraid I have no sources.

And sorry about my previous post; I was arguing for the sake of arguing, not because I thought I was right.

Originally Posted by drowsy turtle

And sorry about my previous post; I was arguing for the sake of arguing, not because I thought I was right.

Thank you. I had been puzzled by your stance.