This.
What we’re kind of asking is “How come all of the elements that we know about are found on Earth?” We have no way of knowing what we don’t know.
There would be essentially zero helium on Earth if it weren’t for alpha decay of radioactive elements. The very name is of course from the fact that it was identified spectrographically in the Sun before ever being found on Earth.
Would a planet lacking heavier elements have a much lower background radiation? If so, would that result in a much lower rate of random mutation, thus making evolution a much slower process - possibly too slow to allow adaptation to environmental changes?
Except there aren’t any more blank spots on the periodic table. We know every element and there’s no room for any more. There used to be holes, but we discovered that those holes were filled by elements with short half lives. Those elements used to be present in the early primordial nebula that eventually formed the solar system but they broke apart into other elements. That’s why there is no technetium in the earth’s crust.
We know what the periodic table looks like. From the properties of the known elements chemists can approximate the properties of heavier elements.
While there may be some hints of an “island of stability” in those heavier elements, virtually all predictions have the stability be relative, i.e. many minutes instead of nanoseconds. Every one will still be radioactive and go through decay, unless all understanding of how protons and neutrons interact when stuffed into a nucleus is wildly wrong.
Nor can weird dark matter or other unknown stuff come to our rescue. The fact that it doesn’t interact with normal matter is a game killer.
Only in science fiction do people come across new and usable elements in space.
Even the rocky planets in our own Solar System vary significantly in the abundances of some elements, both in their crusts and in their overall abundance. For instance, the surface of the Moon has more titanium than does the Earth, and the surface of Mars has more iron. It’s no stretch at all, by science fiction standards, to posit a planet with high enough heavy metal concentrations at the surface to be inhospitable to human life.
Oh, and there is one way in which one might have stable trans-uranic “elements”. For purposes of chemistry, the details of the nucleus are mostly irrelevant: All that matters is its total positive charge, and that it’s much more massive than the electrons. And it is conceivable that you could have a nugget of quarks stuck together, or a microscopic black hole, or something, with a total charge equal to that of 93 or more protons, while still being stable. This would be completely unrelated to the “islands of stability” of nuclei made up of protons and neutrons. And such a charged particle, surrounded by the appropriate number of electrons, would behave almost identically, chemically speaking, to the “normal” element with the same charge on its nucleus.
One thing we know is abundant on Earth but extremely rare in the universe (perhaps even non-existant) is fossil fuels …
Interesting thought.
Actually, we have plenty of those elements on Earth as well; they are fortunately (or unfortunately, depending on your view) down in the mantle or locked up in mineral formations in the crust, or naturally found in trace amounts in seawater. There could be planetary processes that release these more readily on other worlds, e.g. constant vulcanism such as on Io, but these would probably render the world otherwise uninhabitable for us or any life of similar composition. We’ve done a pretty bang up job of freeing and distributing mercury, cadmium, and lead into our environment, however; industrial use of mercury dwarfs all natural geophysical processes of mercury release in volume, and the major avenue for cadmium accumulation is tobacco smoking. The use of lead in various construction materials and food containers–now widely banned in the industrial world–and of course the addition to tetraethyl lead as an antiknock agent in gasoline has lead to vast increases in environmental lead.
Bad science fiction at that. We have a pretty coherent picture of chemistry and the elements, enough to make very accurate predictions using radiometric dating to find the age of the Earth to very high precision. There are no new naturally occurring chemical elements (at least, ones stable enough to stay around) that we’ll find. On the other hand, we could certainly discover bizarre new physics and exotic (non-chemical) matter in neutron stars or hypothetical quark stars, and general relativity is pretty limited about what it can tell us about what goes on in close proximity to a black hole, while quantum field theory lacks a workable description of gravitation. There is plenty left to learn about the universe; just not new chemical elements.
Stranger
Radiation from the decay of heavy elements is not such a major contributor to DNA mutagenesis.
Yet hydrocarbons are abundant on Titan, more so than on Earth. They just aren’t made from fossils.
One hypothetical type of planet that has been suggested is the ‘carbon planet’, where oxygen is locally scarce compared to carbon and the planet consists of a number of compounds low in oxygen and high in carbon. Such a planet could have even greater reserves of hydrocarbons than Titan. Of course, since oxygen would be scarce on such a world, there would be no way to burn these compounds for fuel.
Nope. This is a mistaken meme that radiation is the sole or primary source of mutation in DNA. Various chemicals will cause DNA mutation and, unless you’re in a high radiation environment, are probably a more common cause. These chemicals have various sources: general environment (dust breathed in, for example), food or contaminates thereof, and byproducts of metabolism (free radicals, for example).
ETA: damn ninjas get in everywhere.
And even mutagenic radiation largely originates from either the Sun or from cosmic rays, directly or indirectly (an indirect example would be carbon 14 produced high in the atmosphere via cosmic rays, then eventually making its way into a creature’s body and decaying).
In fact, complex hydrocarbons and even amino acids–the basis of all life on Earth–can be found in interstellar space, produced in planetary nebulae. Titan has more natural gas, and likely petroleum, than all existing reserves on Earth. Hydrocarbon-rich planets and moons are probably reasonably common (based on the commonality of those elements) in any environment that can support an atmosphere. Three of the four solid planets in our system have atmospheres or geospheres which are relatively rich in carbon compounds; in the case of the Earth, much of that is locked up in solid carbonates, clathrate hydrates, and of course, previously and currently living organisms owning to the presence of carbon-based life; and on Mars, most of the atmosphere was apparently lost but what remains is predominately carbon dioxide. And of course, the previously mentioned Titan is thick with hydrocarbons kept (relatively) warm and fluid by tidal energy.
In the absence of oxygen, chlorine and other halogens could act as oxidizing agents, although in order to remain free would require a far more thermally energetic environment than Earth, and given the relative abundance of oxygen (by far the third most abundant element after hydrogen and helium) it is unlikely that it is not found everywhere in the universe.
And of course, there is just plain replication error as well, which occurs rarely but still contributes to genetic drift, and adaptation has less to do with the mutation rate than it does access to materials and energy; an alien form of life could have a slower average rate of mutation but be far more prolific, producing more variation in bulk than in sequence. But there is no particular reason to assume that all life would be based on deoxyribonucleic acid as the coding mechanism; we’ve produced artificial DNA with other nucleotide bases, suggesting that our particular four bases may be somewhat arbitrary, and it is entirely possible that some heretofore unsuspected complex polymer or protein-like structure could fulfill that role in alien life.
Stranger
But such a valuable planet for robot mining. A real gold mine!
Always assuming there is an economic method of shipping back to a human planet. (Which is a pretty big assumption.)
Good point.
What I cant understand is gold. Why is it in only certain places in certain veins?
I’m pretty sure there is no technetium to be found on earth so, technically, all naturally occurring elements can not be found on earth (although there may well have been some in earth’s early years it is pretty much all gone now).
Same as for all other mineral deposits, or at least same set of factors at work.
Virtually all of the concentrated metal ores found in Earth’s crust are either deposited by volcanism or are deposited by meteorite impact; hence why minerals like gold, silver, and copper are found in formerly volcanically active regions, or are found around impact zones such as iron and nickel. Other materials, such as the so-called “rare earth” elements are found widely distributed but in almost trace amounts, making them costly and difficult to extract even from relatively rich deposits of monazite.
Stranger