Two New SETI Biosignature Types

TL;DR

The two proposed SETI signatures are isoprene, a potential sign of biology or technology, and nitrogen dioxide, which could reveal life or industrial pollution. Isoprene may persist in oxygen-poor atmospheres, while nitrogen dioxide could accumulate more readily around type M red dwarfs and type K orange dwarfs. Read on to understand their possible sources, detection challenges, and the planetary conditions that could make them visible.

Transcript

the science behind the search for extraterrestrial life in the universe has made significant leaps in recent years mainly due to improving equipment where it was once a matter largely of searching for powerful alien radio signals studying the search for extraterrestrial life in general now enjoy a host of possible bio and techno signatures that we ... Read More

Key Insights

• 👨‍🔬 Advancements in equipment have expanded the search for extraterrestrial life beyond radio signals.
• 🫢 While certain gases like methane can indicate the presence of life, their origin can be ambiguous, leading to debate.
• 🛟 Isoprene, a compound associated with life on Earth, and nitrogen dioxide, a potential technosignature, are identified as additional biosignatures to be considered in the search for extraterrestrial life.
• 🕵️ Detecting isoprene is challenging due to its similarities to methane and susceptibility to destruction, but under favorable conditions, it may be detectable.
• 🌤️ Nitrogen dioxide detection may be easier around smaller stars, but cloud cover in exoplanet atmospheres can complicate its identification.
• ❓ The detection of biosignatures and technosignatures depends on the specific atmospheric and stellar conditions.
• 🙂 Future advancements in instrumentation offer hope for shedding light on nearby exoplanet atmospheres.

Questions & Answers

Q: What are the two new SETI biosignature types?

The two chemicals proposed for searches of exoplanet atmospheres are isoprene and nitrogen dioxide. Isoprene could indicate biology or technology, while nitrogen dioxide could act as both a biosignature and a technosignature associated with industrial pollution.

Q: Why could isoprene indicate extraterrestrial life?

Isoprene is strongly associated with life on Earth and is emitted by trees, especially oak trees, as well as through many other biological processes. Trees use it to cope with heat stress and produce much less at night than during daylight.

Q: Could isoprene persist in an exoplanet atmosphere?

Isoprene reacts strongly with oxygen-containing radicals, so it would not remain long in an atmosphere like Earth's current one. It may persist much longer in an oxygen-free atmosphere under the right planetary and stellar conditions.

Q: Why is detecting isoprene difficult?

Isoprene can look like methane and is destroyed through photochemical processes and possibly reactions with hydrogen. Detection may still be possible when the planet has the right atmosphere and orbits the right kind of star.

Q: Can isoprene be produced without biology?

The transcript says there is currently no known way to produce isoprene other than biology and technology. On Earth it is also produced industrially, mainly by the oil industry, and is used to make synthetic rubber.

Q: How can nitrogen dioxide be both a biosignature and a technosignature?

Nitrogen dioxide can indicate life, but it can also reveal industrial pollution in an exoplanet's atmosphere. Forest fires, lightning, and other processes can produce it, while the large quantities needed for distant detection would more likely come from an industrial civilization, especially one burning fossil fuels.

Q: Around which stars might nitrogen dioxide be easier to detect?

Nitrogen dioxide might be easier to detect around smaller stars, including type M red dwarfs and type K orange dwarfs. Their light does not break down the molecule as readily as light from larger stars, allowing it to accumulate to potentially detectable concentrations.

Q: How could clouds affect nitrogen dioxide detection?

In a cloudless atmosphere, enough nitrogen dioxide should be visible, but significant cloud cover could mask it. Because clouds are common on Venus, Earth, and even Mars, atmospheric conditions could substantially complicate this technosignature search.

Summary & Key Takeaways

• The search for extraterrestrial life has evolved from focusing on powerful alien radio signals to exploring a variety of possible bio and techno signatures.

• Recent debate has emerged around gases like methane and phosphine, which may indicate life but can also be produced through non-biological processes.

• Two recent papers identify isoprene, a compound strongly associated with life on Earth, and nitrogen dioxide, which can indicate both life and industrial pollution, as potential biosignatures and technosignatures to be searched for in exoplanet atmospheres.