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[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/alien_abduction_507188724.jpg]]
[[caption-width-right:350:Is proof of alien life being hidden in Area 51?]]

->''"A fifth and sixth DNA nucleotide. A new base pair. Agent Scully, what you are looking at... it exists nowhere in nature. It would have to be, by definition... extraterrestrial."''
-->-- '''Dr. Carpenter''', ''Series/TheXFiles'', "[[Recap/TheXFilesS01E24TheErlenmeyerFlask The Erlenmeyer Flask]]"

Physical proof of alien activity.

An object of indeterminate origin has been found. It is sent to a lab for analysis, but the lab cannot identify the material it's made of. Similarly, when the heroes ask the lab to identify the mysterious glowing substance found at the crime scene, the reply may come back: organic-based, but unknown. Sometimes the scientists go so far as to say conclusively that whatever it is, it [[ImportedAlienPhlebotinum cannot be found on Earth]].

Such substances are something of a MacGuffin. Often they do not possess any special properties or behaviors, although at times they are found to be {{Unobtainium}}. The purpose of declaring a substance to be Not of This Earth is to "prove" extraterrestrial origin or activity.

There are several ways to handle this trope plausibly: the substance could be made of known elements that are present on Earth but are far too rare to make an object as big as the one being investigated, or perhaps in isotope ratios not typical of Earth or the Solar System, or else it should be a manufactured substance using techniques beyond Earthly science. Any substance said to be a "new element" is almost by definition implausible, as all matter is made up of atoms, which are made up of protons, neutrons, and electrons; the number of protons is what determines what element the atom is, and the periodic table is very well-mapped out; anything that shows up should slot in exactly where such an element would be predicted to[[note]]Known elements above a certain point are (so far) all highly unstable, and would decay into "lower" elements at almost the same time they came into existence, so they would not make good building materials, at least not without some kind of handwaving or lampshading along the lines of "I don't know how it isn't decaying, but it isn't"[[/note]].

See also HumanAlienDiscovery, which is this applied to a person who discovers he/she's not from this Earth.

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!!Examples:

[[foldercontrol]]

[[folder:Anime & Manga]]
* ''Anime/DarkerThanBlack'' has a lot of this. Besides the AlienSky and {{Differently Powered Individual}}s that suddenly appeared with the Gates, some really weird crap comes out of said Gates. Like stone flowers that grow and can be used to make a drug, a [[MineralMacguffin crystal]] that [[AmplifierArtifact makes Contractors more powerful]], or technology that lets the user [[LaserGuidedAmnesia alter]] [[FakeMemories memories]]. Even the scientists studying them occasionally have to just give up and say that RealityIsOutToLunch.
* Not quite ''aliens'', but the trope comes up in ''Manga/DeathNote''. The police get their hands on a Death Note after the Yotsuba arc, and their lab reports state that the paper matches no known earthly substance.
* When Bulma first examines the namekian spaceship in ''Anime/DragonBallZ'', she says she's never seen anything like it and that it isn't metal. Her father couldn't build his own ship based on it as he couldn't replicate the materials.
* ''Anime/{{Witchblade}}'' is a strange case. In the original, ComicBook/{{Witchblade}} was presented as a reproducing creature (it has parents). ShapeShifting, tank-ripping symbionts have few in common with Terran life. So the creators of the adaptation surrounded it with some alien flora in DreamWithinADream episode endings -- and it doesn't look out of place there.
[[/folder]]

[[folder:Comic Books]]
* ''ComicBook/{{Tintin}}'': In ''Recap/TintinFlight714'', they find an alloy of cobalt and a few common metals. Cobalt is common enough, but cannot be found in this form, apparently.
[[/folder]]

[[folder:Film -- Live-Action]]
* In ''Film/AvengersAgeOfUltron'', when J.A.R.V.I.S. studies the sceptre, he says that it's alien and there are elements he can't quantify.
* In ''Film/{{Clash of the Titans|1981}}'', Ammon says of Perseus's sword:
-->'''Ammon:''' What is this strange metal? It is neither brass nor iron. It is like no metal that I have ever seen... By the gods!... I was right to say "by the gods". Who else could make a sword that slices through solid marble, without leaving the slightest blemish on the blade?
* In ''Film/ManOfSteel'', Jonathan Kent mentions that he had a tiny piece of Clark's ship checked out by a scientist who said that it didn't match anything in the periodic table.
* In ''Film/Predator2'' the creature's weapons are made of metal that doesn't fit in the description of any known element. For a little extra verisimilitude, we actually see the scientist putting a sample into their Spectroscope, and being totally confused by the results.
* In ''Film/SupermanIII'', Richard Pryor's character does an analysis of kryptonite, and the results indicate that a certain percentage of it is simply "unknown". Looking at a cigarette package, he writes in [[spoiler:"tar"]]. The resulting synthetic kryptonite has a rather different effect on Superman than they expected
[[/folder]]

[[folder:Literature]]
* Plutonium-186 in the Creator/IsaacAsimov novel ''Literature/TheGodsThemselves''. Chemists and physicists are befuddled by an isotope of plutonium whose nuclei shouldn't hold together for more than a trillionth of a trillionth of a second, according to the natural laws of our universe. Then, one scientist realizes that the reason plutonium-186 can be stable is because it brought a bit of the physics of its home universe with it.
* ''Gold in the Sky'', the 1958 sci-fi thriller by Alan E. Nourse. The sons of an AsteroidMiner are investigating his death at the hands of an evil mining corporation. They assume he found a rich ore strike and was murdered for it. Halfway through the novel they remove Dad's [[SpaceWestern ancient .44 revolver]] from its holster to defend themselves and discover it's a completely unfamiliar weapon not constructed for human hands, with no hole in the muzzle, yet [[RayGun it can burn a six-foot wide hole]] in half-inch steel plate. It's then they realise the stakes are way higher than illegal claim-jumping.
* Creator/HPLovecraft:
** One of the earliest examples is "Literature/TheColourOutOfSpace" -- where the mysterious GreenRocks are not only an alloy unknown on earth, but of a ''[[FictionalColour colour]]'' unknown on earth.
** An idol depicting the eponymous EldritchAbomination appears in "Literature/TheCallOfCthulhu"; it's made out of stone that scientists are unable to identify. The matter from which it was made was brought to Earth by the Great Old Ones.
** "Literature/TheWhispererInDarkness" contains artifacts made of a metal unknown on Earth, mined on the dark planet Yuggoth. It's also inverted, as part of their motivation for coming to Earth is to mine minerals that aren't found on their home world.
* ''Literature/TheNanoFlower'': The eponymous flower is delivered by a HighClassCallGirl to Julia Evan's personal assistant. The flower is from Julia's husband who's been missing for some time; it doesn't appear in any botanical database and has DNA coding that's thousands of years in advance of anything on Earth.
* Zig-zagged in ''Literature/{{Sphere}}''. At the start of the story, a sample of the hull of a supposed alien ship is analyzed and found to be made of common elements, but they've been worked into a composite form that nobody on Earth can yet duplicate. [[spoiler: It turns out that the ship is from the ''future'' and was built on Earth after all... but ''then'' the titular extraterrestrial artifact is found in the ship's cargo hold. The protagonists can tell just by looking at the sphere that it's "something alien".]]
[[/folder]]

[[folder:Live-Action TV]]
* In several episodes of ''Series/DoctorWho'' over the series run. At one point the Third Doctor specifically was testing for something that he knew couldn't exist on Earth.
* Cleverly averted in an episode of ''Series/TheEqualizer''. The title character helps a street crazy who claims to be an alien; it turns out the man is actually a brilliant research scientist who presumably snapped when corrupt execs forced his invention away from him... however, at the end, he's disappeared, and it's discovered that the metal medallion he left behind "was manufactured in a vacuum." "You mean," the Equalizer demands, "this thing was made in ''outer space''?" His assistant shrugs and grins. "They just don't know." [[note]]It is possible to create vacuum conditions on Earth for experimental/manufacturing purposes.[[/note]]
* Subversion: In the ''Series/{{House}}'' episode "Cane and Able," Chase removes a small piece of metal from the shoulder of a boy who claims he has been abducted by aliens.
-->'''House:''' The results came back. The lab cannot identify the metal. Said it might not even be terrestrial.\\
'''Dr. Chase:''' Really?\\
'''House:''' No, you idiot. It's titanium.
* ''Series/{{Luke Cage|2016}}'': The Judas bullet, designed by Hammer Industries, is capable of piercing Luke Cage's bulletproof skin, and is made from metal salvaged from [[Film/TheAvengers2012 the Chitauri's warships]].
-->'''Shades:''' The rounds are a composite, invisible to metal detectors. And they incinerate forensic evidence, so they are untraceable.\\
'''Cottonmouth:''' What kind of metal does that?\\
'''Shades:''' Nothing from this Earth.\\
'''Cottonmouth:''' The Incident?\\
'''Shades:''' That's what I hear.
* ''Series/TheOuterLimits1995'': In "Sacrophagus", an amber-like cocoon is discovered in a Neolithic burial chamber in UsefulNotes/{{Alaska}}.
* The odd watches carried by angels on ''Series/PortCharles''. Victor's lab cannot identify the metal.
* ''Series/SaturdayNightLive'''s iconic HappyFunBall is said to be made from an unknown glowing substance that fell to Earth from outer space.
* Occurs in ''Series/{{Smallville}}'' with kryptonite, various Kryptonian devices, and other alien materials.
* ''Series/StargateSG1'':
** Done with a Jaffa in the pilot episode.
--->'''Doctor:''' ''[removing a larval Goa'uld]'' It's not human!\\
'''Jack O'Neill:''' Ya think?
** Very early episodes treated Naquada like this; before they learned the name, they referred to it simply as "the Stargate element," because it was unknown on Earth.
** There is super-strong/light metal trinium.
* [[SiliconBasedLife Silicon-based biotic material]] or DNA containing more than four bases are sometimes mentioned in ''Series/TheXFiles''. For instance in "[[Recap/TheXFilesS01E24TheErlenmeyerFlask The Erlenmeyer Flask]]", a scientist is baffled by Scully's sample. Surprisingly for Scully, it is not monkey pee, but extraterrestrial material.
-->'''Dr. Carpenter:''' A fifth and sixth DNA nucleotide. A new base pair. Agent Scully, what you are looking at... it exists nowhere in nature. It would have to be, by definition... extraterrestrial.
[[/folder]]

[[folder:Theater]]
* In ''Theatre/TheRockyHorrorShow'', Doctor Scott tries to distract Brad from realizing that Frank has outed him as Nazi by pointing out that a nearby machine is made of a metal that is not of this Earth and probably from another planet.
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[[folder:Video Games]]
* Subverted in ''VideoGame/Condemned2Bloodshot''. One of the [=TVs=] displays an interview with a scientist who has been analyzing samples of the metal that the Oro Invictus use to enhance their powers. When he explains that he cannot place the origin of the metal fragments, the interviewer immediately suggests that the metal pieces fall under this trope. However the scientist shoots this theory down, stating that the pieces ''are'' of Earthly origin; they're just made using a previously-unknown manufacturing technique.
* Simultaneously played straight and inverted in the backstory for ''VideoGame/{{Homeworld}}'': The first solid proof that the Kushan race did not evolve on Kharak was that when they developed the ability to directly examine DNA samples, they could find absolutely no shared genes with any other lifeform on the planet except for their own gut flora and one species of small mammal that was probably descended from a pest species they brought with them unwillingly. Prior to that they also had evidence of a large amount of metallic debris in orbit, which when samples were collected and returned to the surface for analysis proved to be a highly complex alloy that pushed their understanding of metallurgy by decades once they were able to reverse-engineer it, but that wasn't definite evidence of anything but the fact some AncientAstronauts had spent some time in orbit of Kharak; only when the DNA sequencing results were published was it confirmed that the Kushan ''were'' those astronauts.
* ''VideoGame/ShinMegamiTenseiIV'': Neither Sanat nor the Ancient of Days are made of materials native to the Universe, which only further proves how ''alien'' they are to it. Scans only end in ''Error'' messages.
* ''VideoGame/XCOMUFODefense'' has both a straight example and a subversion:
** [=UFOs=] are powered by Elerium-115, which can only be obtained by capturing ships with their reactor intact.
** [=UFOs=] are made of "alien alloys", but once reverse-engineered, it turns out those alloys can be produced using Earth technology.
[[/folder]]

[[folder:Webcomics]]
* ''Webcomic/GrrlPower'': Subverted. Deus (with great difficulty) manages to find the geode that contained the substance that gave Maxima her powers. He didn't find anything particularly interesting, just a few exotic isotopes, "but nothing we've never seen before." TheRant specifically mentions that the idea of elements not on the periodic table is silly, since we have the periodic table pretty well mapped out.
[[/folder]]

[[folder:Web Original]]
* A recurring trope in the Website/SCPFoundation. Though they're usually pretty good at identifying the materials (or at the very least their presentation, i.e. being alloys or mixtures) their physical anomalous artifacts are composed from through mass spectrography testing, sometimes they find themselves unable to ascertain.
[[/folder]]

[[folder:Western Animation]]
* ''WesternAnimation/SupermanTheAnimatedSeries'':
** In "Knight Time", Superman and Robin's search for Batman uncovers evidence that he was targeted by mind-controlling nanites. They capture the Mad Hatter, who [[NotMeThisTime denies involvement]] and, when allowed to examine the nanites, declares them to be beyond any technology he's seen and suggests an alien origin. Admittedly, alien origin (e.g. Supes himself) is rather less unusual in this universe.
** Before that, in "A Little Piece of Home," Luthor is amazed when he sees Superman suddenly collapse from exhaustion after passing too close to a display of gems in a museum display case. After analyzing them in his lab, he finds that one particular green stone isn't on the periodic table, and almost certainly came from space.
[[/folder]]

[[folder:Real Life]]
* A standard element in alien crash cover-up conspiracy theory. Some people claim to have found some metal debris near the crash site, allegedly part of the alien ship. Said metal usually is strangely light, yet highly resistant to impact (often said to be bulletproof). To this date, no such metal has been subjected to public scrutiny.
* A historical real life example is [[http://en.wikipedia.org/wiki/Helium Helium]] -- the second most common element in the entire universe as we currently understand it -- which was detected and identified as a new element by analyzing the spectrum of the Sun's chromosphere in 1868, 14 years before the same spectral line would be first detected on Earth as well and 27 before the element itself could be properly isolated here. In fact, all the other noble gasses were similarly unknown as elements until well after much rarer ones had been discovered and studied.
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