Broccoli expels methyl bromide, which the study claims is could be a particularly interesting gas to … [+]
Back in September 2020 the chemical phosphine (P3) was identified in the atmosphere of Venus. It was tentative, much-argued about and later cast into doubt, but it was an exciting detection for astrobiologists because phosphine is created on Earth only by bacteria and microbes. Or possibly volcanoes.
In the end it was largely viewed as evidence only for anomalous and unexplained chemistry on Venus.
What chemicals should astrobiologists be searching for on planets? Gases that are only byproducts of biological life of some kind or other. That could mean looking for a gas produced by broccoli, according to a new study published this week in the Astrophysical Journal.
All plants and microorganisms on Earth expel toxins as gas. Specifically they add a carbon and three hydrogen atoms to a chemical element in a process called methylation.
Broccoli expels methyl bromide, which the study claims could be a particularly interesting gas to look for in the atmospheres of red dwarf planets—cool stars that make-up about 70% of all stars we know of in our Milky Way galaxy.
Artist’s conception of an M dwarf planetary system, where methyl bromide is more likely to be … [+]
Methyl bromide could be a good gas to look for because it remains in the atmosphere for a shorter time than traditional biosignature gases. “If you find it, the odds are good it was made not so long ago—and that whatever made it is still producing it,” said Michaela Leung, UCR planetary scientist and lead author of the study. “There are limited ways to create this gas through non-biological means, so it is more indicative of life if you find it.”
Methyl bromide does exist on Earth but it’s hard to find because it’s destroyed by the Sun’s UV light. So it would be most easily be found on planets around red dwarf stars (also known as M dwarf stars) where UV light is much less intense. “An M dwarf host star increases the concentration and detectability of methyl bromide by four orders of magnitude compared to the sun,” said Leung.
“We believe methyl bromide is one of many gases commonly made by organisms on Earth that may provide compelling evidence of life from afar,” said Eddie Schwieterman, UCR astrobiologist, study co-author and leader of Leung’s research group. “This one is just the tip of the iceberg.”
Wishing you clear skies and wide eyes.
