Lab Discovery Presents New Challenge in the Search for Alien Life

The most probable method for detecting life on a distant exoplanet is by identifying a biosignature. This involves analyzing the atmospheric spectra of the planet to find the distinctive spectral pattern of a molecule that can only be produced through biological activity.

Although it seems straightforward, detecting life on exoplanets is far from simple. The presence of basic molecules like water and oxygen doesn’t confirm the existence of life, as geological processes can also generate significant amounts of oxygen. While Earth’s oxygen-rich atmosphere is largely due to life, it’s not the only possible source.

The Limitations of Traditional Markers

Moreover, as a recent study reveals, some molecules we’ve long considered as biological markers might not be exclusive to life. Ideally, astronomers would prefer to find evidence of a complex molecule like chlorophyll. However, chlorophyll is unlikely to exist in large quantities in an atmosphere, making its spectral pattern faint and difficult to identify.

As a result, astronomers typically focus on simpler, yet distinctive, molecules. One such molecule is dimethyl sulfide (DMS), or (CH3)2S, which on Earth is produced only by phytoplankton, making it a strong candidate as a biosignature—or so it was thought.

In the new study, researchers successfully synthesized DMS and other sulfur-based molecules in the lab without any biological input. Although this doesn’t prove the process occurs naturally, the team further demonstrated how DMS could potentially form on a planet with a dense organic haze.

Demonstrating the Potential for Abiotic DMS Production

We know planets like this exist because Saturn’s moon Titan is one such example. If Titan were closer to the Sun, ultraviolet radiation could be strong enough to initiate the chemical reactions needed to produce DMS.

If Titan were in Earth’s orbit, distant aliens would detect DMS in the atmosphere of a planet within the Sun’s habitable zone. It would seem like strong evidence for life, but Titan would still be inhospitable to life as we know it.

However, Titan could host some form of exotic life, which is another takeaway from this study. While the authors demonstrate that DMS or similar molecules alone don’t confirm the presence of life, they suggest it would indicate a high potential for it.

Essentially, a warm planet with a dense organic haze in its atmosphere would likely contain the complex organic molecules necessary for life to evolve. The existence of DMS on such a world, therefore, would at least imply the potential for life.

This study underscores the need for caution when interpreting certain molecules as biosignatures, but it also reinforces what exo-biologists have suspected for a while.

Discovering life on another planet probably won’t come from a single dramatic moment. Instead, several planets may show chemical markers hinting at the possibility of life. As we identify more of these potential biomarkers in their atmospheres, our confidence in the existence of extraterrestrial life will grow steadily.

Read the original article on: Science Alert

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