Here is an idea that likely never crossed the mind of most space enthusiasts – a gas emitted from broccoli (and other plants) is one of the most indicative signs of the existence of life on a planet.
According to a recent study by researchers at the University of California Riverside, this is true.
The gas methyl bromide has been associated with life on Earth for a long time. It naturally occurs in plants as a result of their defense.
The defense process of methylation allows plants to expel foreign contaminants such as bromide by attaching a series carbon and hydrogen atoms. This gasifies the plant and allows it to escape into the atmosphere.
From an astrobiological perspective, methyl bromide is particularly interesting. It was used until the 2000s as a pesticide and it has several advantages over potential biosignatures if it appears in an exoplanet’s atmosphere.
It has a short life span in the atmosphere of a planet. This is important for exoplanet search, because it indicates that the process producing the gas may still be active. It is not a result of an event in geology that occurred eons ago.
A second advantage is one that all astrobiologists love to see – there are very few non-biological processes that produce the gas, and even those processes aren’t typically natural.
Although methyl bromide is now a dangerous chemical, it was still used in large quantities as a pesticide. It was not regulated because of its harmful health effects.
A third advantage is the spectroscopic wavelength it shares with a ‘cousin’ gas that is also a biosignature – methyl chloride, which also results from the methylation process.
They would be much easier to spot from faraway and they both indicate the existence of a biological procedure. However, it is difficult to distinguish between methyl bromide and methyl chloride, since methyl chloride was already seen around stars, which suggests that this was probably caused by an organic process.
Although not a significant advantage, it is interesting to note that methyl bromide would be difficult to detect from faraway in Earth’s atmosphere.
Its concentrations are sufficient, but UV light from the Sun causes water molecules within the atmosphere to separate into compounds that eliminate the methyl bromide. As a result, it is not present for very long in Earth’s atmosphere.
UV lightThis is only an issue for Sun-like stars. There would be less UV radiation around stars like M-dwarfs which are 10x more common than sun-like star in the galaxy, and this would allow the methylbromide molecule to be broken down.
Astrobiologists will likely look first at these M-dwarfs, and there may be an opportunity to detect methyl bromide.
But such a discovery might need to be rescheduled. Even the JWSTThis isn’t a system that can detect trace elements in exoplanet’s atmosphere.
Some ground-based telescopes, however, will be able to handle the task in the near future. Astrobiologists who are interested in this fascinating biosignature will have to wait until they come online.
This article was first published by Universe Today. Learn more Original article.
