Not long ago I asked about pH indicators and their use in making fantastical skin colors (pH Indicators and Fantastical Skin Colors)

In that question, I listed bromothymol blue as a type of indicator that could serve this purpose. I was then politely informed that bromothymol blue is not an organic pigment, and that it can't be created in nature

My main question is as follows: is there any kind of biology (e.g. Not carbon based) that would make this pigment useful as a biological pigment?


1 Answer 1


Bromothymol blue certainly isn’t synthesised naturally by the biochemistry of earth, but that does not to mean to say it could not be synthesised by an alien biochemistry.

There are millions of complex organic reactions that occur in nature today for example look at this diagram of metabolic pathways which shows just a tiny fragment of what happens in nature every second.

metabolic pathways

So if evolutionary pressure was “ingenious” enough to come up with chlorophyll to absorb blue and red light


I would have thought that given different evolutionary pressures in a different biosphere the same evolutionary biochemical ingenuity would have been capable of synthesising blue pigments like bromothymol blue if it needed them.

bromothymol blue

In fact it would probably come up with a range of blue compounds that were far more energy efficient to synthesise unless there was a very special reason why bromothymol blue was important.

Some reasons why bromothymol blue might be preferred or important include a light spectrum that made bromothymol blue particularly effective and useful and a planet with widespread easily accessible bromine sources.


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