(ORDO NEWS) — Here’s an idea that probably never occurred to most space enthusiasts: the gas given off by broccoli (and other plants) is one of the most telling signs of life on the planet.
At least according to a new study by researchers at the University of California, Riverside.
This gas, methyl bromide, has long been associated with life on Earth. This occurs naturally in the process of plant self-defense.
Methylation, known as a defense process, allows plants to remove foreign pollutants such as bromide by attaching a series of carbon and hydrogen atoms to it, thereby gasifying it and allowing it to escape into the air.
Bromomethyl, in particular, is interesting from an astrobiological point of view. It was used as a pesticide until the early 2000s and has several important advantages over other potential biosignatures if found in an exoplanet’s atmosphere.
First, it has a relatively short lifetime in the planet’s atmosphere. This is especially important for the search for exoplanets, as it means that any process that produces the gas is most likely still active. Its presence is not just the result of a geological event that occurred many millennia ago.
The second advantage is what all astrobiologists like to see: there are very few non-biological processes that produce gas, and even these processes are generally not natural.
Although now considered a hazardous chemical, methyl bromide was produced in large quantities for use as a pesticide before it became regulated due to its adverse health effects.
The third advantage is the spectroscopic wavelength it shares with its “related” gas, which is also a biosignature, methyl chloride, which is also the result of the methylation process.
Their combined signature will make them much easier. detect from afar, and both indicate the existence of a biological process, although they are able to distinguish between methyl chloride and methyl bromide, since methyl chloride has already been seen around some stars, which was probably caused by an inorganic process.
Not exactly adventurous, but an interesting feature of the ability to detect methyl bromide is that it would be relatively difficult to detect in the Earth’s atmosphere from afar.
Concentration levels are quite high, but ultraviolet light from the sun causes water molecules in the atmosphere to break down into compounds that remove methyl bromide so it doesn’t last long in Earth’s atmosphere.
Ultraviolet light is only a problem for stars like the Sun. Around stars such as M-dwarfs, which are 10 times more abundant in the galaxy than sun-like stars, there will be less UV radiation that could destroy the methyl bromide molecule.
Because these M dwarfs will be among the first places astrobiologists look at, they could be a chance to see methyl bromide build up in their atmospheres.
However, any such discovery may have to wait a bit. Even JWST is not set up to detect trace elements in an exoplanet’s atmosphere.
However, in the next few years, some ground-based telescopes will cope with this task. Hopeful astrobiologists will have to wait until they are online before they can really look for this very interesting biosignature.
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