If I understand correctly, besides hydrogen and helium, all of the elements on the periodic table up to Iron came into existence as a result of supernovae explosions. Elements beyond iron require a special type of binary pair supernovae involving one star cannibalizing the other. How is it possible that all of the elements somehow coalesced on earth, considering they come from different sources? Do all rocky planets somehow contain all of the elements?
Why would they not? The materials having been ejected into the universe at large over billions of years, one would expect that just about everything would exist just about everywhere where planet-making material was coalescing by the time the Earth was putting itself together.
The sun/solar system is a population I star (relatively young) and contains elements from population II and III stars.
More here : Stellar population - Wikipedia
Also, all the matter of earth combined doesn’t even come close to 1 percent of the Sun’s mass which is 333,000 times that of earth.
We are stardust…
I’m not convinced it is an easy answer. The OP’s point about some of the elements needing what what are reasonably rare events to create, might lead one to expect that even after a few billion years the concentrations of different matter might not yet be all that homogeneous. The galaxy isn’t homogeneous, and the dust lanes streak around the structure. It would be very interesting to see an analysis of the expected rate of events like neutron start mergers throughout the galaxy versus the rate of mixing and dispersing of matter as the galaxy evolves.
Cosmological principle would suggest that there is indeed adequate production and mixing over time, anthropic principle provides a get out clause if this isn’t the case.
Probably, but the proportions of each of the elements in the earth, or all rocky planets, may be way out of synch with their proportion in the whole universe.
It doesn’t seem too surprising to me.
There were 8-9 billion years of star formation, destruction and material distribution before our sun ever came into being. The heavy elements come from the more massive stars which only live a fraction of time that our sun does, perhaps only a few million years. There has been plenty of time for hundreds or even thousands of distribution cycles of these heavier elements across the galaxy. Not so surprising then that the mix of heavier elements encounters those rarer conditions that allow formation of the very heaviest elements and that consequently, after billions of years of creation, explosion, accretion, creation, explosion accretion etc, etc, we find ourselves in a solar system that contains traces of all the naturally occurring elements.
To invoke the weak anthropic principle: we can, after all, only ask this question on a rocky planet that can support the evolution of complex life.
First, is some kind of biochemistry plausible elements created by supernovae, neutron star collisions, or other extreme events? Going by a couple different periodic tables showing the origin of each element, and off-the-top-of-my-head biochemistry, I’d guess yes. A “primitive” rocky planet would at least have CHONPS and a lot the trace elements that are essential for life as we know it. A few that are critical for certain major processes on Earth are missing. However, I suspect that alien life could do without iodine (required for thyroid hormone metabolism) or other trace elements involved in relatively exotic metabolic processes. So my WAG is that some sort of life could evolve on a primitive rocky planet.
Second, is life going to survive very long early in a galaxy’s life? Perhaps a galaxy that has not yet had enough supernova to spread around all the elements will be in a stage that is hostile to life. My layman’s understanding is that the earlier populations of stars were huge and had short lives ended by catastrophic events. If supernovae are frequent enough, they might have regularly annihilated primitive life that was evolving on planets that didn’t have heavy elements.
The anthropic principle only applies if human life couldn’t exist without, say, Tantalum or Astatine.
Yeah, true. It is hard to get to any elements past iron that we are dependant upon. Even in the most trace amounts.
A technologically advanced species that has enough knowledge to know about these elements might perhaps have such a precondition, but I doubt it. 
Just to reiterate my earlier point a bit more clearly. Our current knowledge is that massive star novae only account for the lighter elements. The get the heavier ones, and especially the really heavy elements, the only known process is the merging of two neutron stars. This isn’t a process that was bounding along in the early universe, in fact if we look at the young galaxies out there, we can see that they have no heavier elements. We need to wait quite some time before things settled down to the point where neutron stars are being produced, forming in binary systems and then finally merging. Stellar nucleogenesis of elements much past Ruthenium (atomic number 44) is dominated by this process. So the question becomes one of the expected number and merging rate of binary neutron stars, and the mixing of their products into later star forming dust lanes.
It applies if the same process that creates some of the essential elements also create others.
I see no problem with having all the elements located here on Earth in (at least) tiny tiny amounts … I’m basing this on sulfur’s #10 ranking in abundance in the galaxy yet still only 440 ppm … is there any reason to assume that the stars that ended as supernovae and formed our Sun weren’t themselves Population I stars rich in “metals”? … we do know they did go boom, so we know they were big suckers …
Are they, though?
Are any of the transuranic elements formed ion supernovas? I don’t know, but I suspect they are. Then they decay, and are gone long before they form part of a planet.
in.
Plutonium 244 is produced in supernovae
According to this page, the amount of uranium in our solar system was the result of around 10 supernova explosions.
It is improbable that any form of life would be dependant upon astatine given its propensity to decay almost immediately. But yes, we’re primarily made of the most abuntant elements that can form chemically stable strictures (carbon, hydrogen, nitrogen, oxygen, phosphorous, sulphur) and traces of other elements (potassium, sodium, selenium, iron, et cetera). The anthropic principle of any flavor need not be invoked; there are many high metallicity regions and star systems in which similar distributions of elements may be found through specstroscopy of stars.
As for where all of these elements came from, as K364 says, we are the residue of previous, more short-lived stars. (The Carl Sagan quote is actually, “The cosmos is within us; we are made of star stuff.” The vast majority of naturally occuring elements heavier than sulphur, and all heavier than iron are produced by various stellar nucleosynthesis processes of energetic neutron emission and capture (r-process and s-process), proton capture (P-process and Rp-process) and the remaining elements are produced by radioactive decay. am77494 notes the progression of stellar populations from the very short-lived supergiant Population III stars formed from the primordial soup of various hydrogen and helium isotopes as well as a very small amout of lithium-7 and produced the first supernovae; the next progression of metal-poor Population II stars made from those residues and producing the materials for our metal-rich Population I star. Note that while this is a succession of classifications it is not a literal sequence but a segragation; we have a mix of Pop I and II stars in our galaxy and presumably in all other galaxies although in different propotions depending upon configuration.
Although stellar nucleousynthesis is responsible for most heavy elements there has been conjecture that some are produced by neutron star collisions, and many stellar processes are driven or accelerated by interactions between companion stars, one feeding the other material, or a supernova creating ejecta and shockeaves inducing companion stars into nucleosynthesis processes it would otherwise not be energetic enough to do on its own. There is a lot of speculation, primarily based on models and simulation which are themselves speculative. The inability to observe supernovae and other nucleosysnthesis processes directly forces astrophysicists to make a lot of assumptions based on very sparse data, and pretty much every revelation in cosmology and stellar astronomy upends existing models to a certain extent as astrophysicists discover new mechanisms in star formation and evolution.
As for our system and planet, we are the result of the residue of at least ten seperare nucleosynthesis events beyond early Population III nucleosynthesis (as determined by ratios of long lived isotopes of heavy elements) and the Earth has the highest metal content of any planetary size body in our solar system. Some of these events are at least 8–9 Bya (some are likely older), and may have even come from extragalactic sources. We are a chef’s special stew of the history of stellar evolution living in the suburbs of a relatively mature galaxy, and it is unsurprising that we have a cross section of heavier elements.
Stranger
The universe is unimaginably vast. There could be plenty of stuff out there we don’t even know about.
In the Honor Harrington novels by David Weber, the planet Grayson is barely habitable by humans because of an abundance of toxic heavy elements: lead, mercury, cadmium, arsenic, antimony, etc. Could such a planet exist if it was formed from a nebula that happened to be particularly enriched in heavier than iron elements?