I was wondering if and how astronomers have/had detected the molecule Tetrahydrocannabinol (THC), commonly known for it's effects in marijuana, in space.

I had previously seen a hoax regarding the drug being detected on an exoplanet, but I wanted to know if there was any possibility of it.

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    $\begingroup$ Why was this downvoted? Does someone wish to maybe offer an explanation to improve my question instead? $\endgroup$ Mar 4 '16 at 16:26
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    $\begingroup$ Ultraviolet Spectrum Peak 276.5 nm FTIR shows nothing remarkable: sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/… , sopicking out the molecule in space is going to be hard. $\endgroup$ Apr 28 '19 at 16:47
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    $\begingroup$ I’m voting to close this question because 1) I believe it is... well.... sub-optimal from a scientific view 2) I want a completely politics-free Astronomy SE. $\endgroup$
    – peterh
    Jul 23 '20 at 7:50
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    $\begingroup$ There's plenty of ethanol though. $\endgroup$
    – ProfRob
    Jul 23 '20 at 8:09
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    $\begingroup$ I'm voting to leave this open: biosignature/biomolecule detection seems like a perfectly reasonable topic here, even for molecules that are regulated in various parts of the world due to having psychoactive effects (see also: ethanol). A question on the politics of psychoactive molecules in space would be off-topic, but that's not the focus here. Furthermore a completely politics-free Astronomy SE is probably not a reasonable or necessarily desirable goal: there are definitely issues where politics and the astronomy intersect. $\endgroup$
    – user24157
    Jul 23 '20 at 9:39

The detection of complex organic molecules, often abbreviated as COM in astrochemical literature, has only taken up pace in the last couple of decades since substantial advances were only made possible with the advent of new, high-end observational facilities (Green Bank Telescope (GBT), Very Large Array (VLA), Atacama Large Millimeter/Sub-Millimeter Array (ALMA), etc.) in the radio-regime, where specific fingerprints of rotational, vibrational or ro-vibrational transitions are possible to observe.

An regularly updated list of detected molecular species in space can be found at the Cologne Database for Molecular Spectroscopy (CDMS), maintained by the Universität zu Köln. In the table below, you can immediately see that only four organic molecules have so far been detected that are made out of more than 12 individual atoms. However your molecule of interest, Tetrahydrocannabinol (THC), is constituted by 53 (!) individual atoms as one can infer from its chemical forumlae: $C_{21}H_{30}O_{2}$

Its going to be almost if not certainly impossible to ever detect THC in an extraterrestrial environment through remote observations (i.e. sending rovers or other space exploration mission for in-situ explorations is another story altogether). Furthermore, THC would need to be in detectable quantities in an exoplanets atmosphere or within a molecular cloud in interestellar space. A scenario which is missing any arguments or evidence about a process or mechanism that could provide such a high density. The existence of detectable amounts of THC in interstellar space is hindered by the harsh enviroments, e.g. X-ray and UV-fields from nearby stars that would not allow any high concentrations of very large molecules. Furthermore, I believe THC is a biogenic molecule, i.e. not being created except for biochemical processes in terrestrial lifeforms or - of course - as synthetical variant in chemical laboratories. I am not aware of any non-biogenic process that could provide for high THC concentrations in a planets atmosphere. That would make it a dream candidate as a biomarker, i.e. a molecule whose presence alone would strongly hint at biological/xenological activity. Anyhow as a consequence, the feasibility of the detection from THC fails on numerous levels, thus making the detection via telescopes virtually impossible, from at least what we know so far about how, where in what typical quantities THC is formed.


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