An artist's illustration of an exoplanet ocean world. Depositphotos.

“Broccoli Gas,” an Unmistakable Biosignature For Alien Life

Methyl bromide, produced by broccoli and other vegetables in the brassica family could be used to search distant alien worlds for signs of life.


To expel toxins, broccoli and other plants emit gases. According to scientists, these gases may prove there is life on other planets. The gas is formed when an undesirable chemical element is combined with three hydrogen atoms and carbon. As a result of this process, potential toxins can be converted into gases. These are then safely carried away into the atmosphere through methylation. Telescopes could detect these gases in another planet’s atmosphere, indicating the existence of life there.

Michaela Leung, a planetary scientist at UCR, said that methylation is so widespread on Earth that it is expected to occur anywhere. In addition to excreting harmful substances, most cells also have mechanisms to eliminate them. In the search for life beyond our solar system, methyl bromide, one methylated gas, has several advantages over other gases. Several of these advantages were explored and quantified by Leung in a research study published in the Astrophysical Journal. For example, compared with traditional biosignature gases, methyl bromide lasts for a shorter period of time in the atmosphere.


Methyl bromide

Leung says that it was likely manufactured not too long ago if you find traces of it. Whatmore whatever made it may still be making it. Furthermore, methyl bromide will likely be made by living organisms rather than by microbes, which can make methane. As an alternative, methane could have been formed by a volcano or another geologic process. It is more indicative of life if you find this gas since non-biological means are limited to creating it.”, the researcher explained. Also, methyl bromide absorbs light near methyl chloride, a “cousin” biosignature.


While methyl bromide is extremely common on Earth, its presence in our atmosphere is difficult to detect because of the sun’s UV light. When ultraviolet radiation strikes the atmosphere, it starts chemical reactions that destroy the gas by breaking up water molecules. Nevertheless, the study found that methyl bromide could be detected more easily around an M dwarf star than in our solar system. Compared to our sun, M dwarfs are smaller and cooler, emitting less UV radiation that breaks down water. “An M dwarf host star increases the concentration and detectability of methyl bromide by four orders of magnitude compared to the sun,” Leung said.

Looking at M-Dwarf stars

Due to their abundance, M dwarfs will be the first targets in upcoming searches for life on exoplanets. This is because they are more than ten times as common as stars like our sun. As a result, scientists expect astrobiologists to begin considering methyl bromide for future missions and for upcoming telescopes searches for alien life. A number of extremely large ground-based telescopes coming online at the end of the decade will offer a great chance of detecting Earth-like planetary atmospheres around other stars. Moreover, they will be able to analyze the atmospheres of those planets more effectively.

UCR revealed that scientists are interested in investigating other methylated gases as possible targets in the search for extraterrestrial life. Due to their close association with life, this group of gases is significant. According to Eddie Schwieterman, UCR astrobiologist and study co-author, methyl bromide may be one of many gases produced by organisms on Earth that provide compelling evidence of life from afar. “This one is just the tip of the iceberg.”


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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