Methyl bromide is a marker of life on other planets

Some plants produce gases that help them get rid of residual toxins. Scientists have decided to use this fact to search for life in space.

Ok… But why this unfortunate broccoli?

The process of removing methyl bromide from the plant is called methylation (of course, the methylation process can produce different gases, but we’re currently focused on methyl bromide. We’ll explain why below). When the body wants to get rid of an unwanted element, a carbon atom and three hydrogen atoms attach to it, causing the unwanted toxin to escape into the atmosphere along with the gas. Not only broccoli is capable of this, of course, but also all other vegetables from the cruciferous group, as well as very simple algae.

Scientists at the University of California, Riverside say this effect is so common on Earth that it can be assumed that organisms on other planets would get rid of toxins in much the same way. Planetologist Michael Leung says:

Methylation is so widespread on Earth that we expect life could perform it anywhere else. Most cells have mechanisms for excreting harmful substances.

Methyl bromide as a marker

This gas has several advantages over other gases traditionally used to search for life in space (for example, phosphine).

  • First, methyl bromide stays in the atmosphere for a shorter time than other biosignature gases, so if we detect it, we are sure that it did not form thousands of years ago and that something may still be producing it on the planet.
  • Second, it is more likely that methyl bromide was produced by living organisms. Other gases, such as methane, that microbes can produce may have been created by volcanic processes. There are very few non-biological processes that can produce methyl bromide.
  • Third, the marker absorbs light in close proximity to another biological gas: methyl chloride. This makes it easier to track them when they are paired and increases the chances of detecting life.
  • Although methyl bromide is very common on earth, it is not easy to detect it in our atmosphere, because the sun’s UV radiation destroys it very quickly. This leads us to the conclusion that we should look for it in planets that orbit stars unlike our Sun. The California team concluded that planets around a star like an M dwarf star would provide the best conditions for such gas to survive in the planet’s atmosphere. M dwarfs are smaller and cooler than our sun and produce less UV radiation. This is good news because such stars are about 10 times more common in the universe than solar-type stars, giving astronomers a huge area to study.

So how is the research going?

Although the James Wbb Space Telescope (we’re still in awe of the photos it took) isn’t particularly optimized for detecting planetary atmospheres around observed stars, many ground-based telescopes adapted for that purpose will be launched by the end of the decade. Astronomers also plan to better adapt the next telescopes we put into orbit for this job (like the retired Spitzer telescope, but better).

A team in California is studying the potential of residual methyl gases as biomarkers, and methyl bromide is only the tip of the iceberg. And we eagerly await the first confirmed signal of a planet bearing the imprint of life (and who knows, maybe even intelligent life. After all, the Drake equation makes it possible).


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