A research team headed by David Catling, a planetary scientist, and astrobiologist at the University of Washington has found a specific chemical combination that could reveal the existence of life forms on other planets. During the study, researchers analyzed the atmospheric contents of ancient and present-day earth, and finally discovered the chemical combination which they call biosignatures.
Scientists have discovered thousands of exoplanets, and among them, there are several planets which are placed at the right distance from their stars. According to experts, this optimal position makes them suitable for life, as it may possess liquid water. With the help of advanced telescopes, scientists are trying to figure out the presence of biosignatures in these planets. The research report is published in Journal Science Advances.
Experts believe that certain planets may not possess life even though they have the right ingredients to support it, and in these times, analyzing the biosignatures will help to figure out whether there are any living forms there.
According to scientists, biosignatures are a particular mixture of molecules that would not exist without life. To discover it, researchers examined the earth in three different stages; the Archean (4 billion to 2.5 billion years ago), the Proterozoic (2.5 billion to 541 million years ago) and the Phanerozoic (541 million years ago to the present). After the analysis, researchers found that the nature of the earth in these three different stages is very different.
"The phrase earth-like does not refer to a planet that necessarily resembles modern-day earth at all. It's actually a very broad term that encompasses a broad variety of worlds. It includes hazy worlds like the Archean; it includes icy worlds like the 'snowball earth' intervals; it includes anoxic worlds with exclusively microbial ecosystems; it includes worlds with complex and intelligent life, and it includes worlds that we haven't even seen yet," said Stephanie Olson, co-author of this study.
Even though the nature of the earth is very different in these three phases, each of these periods shared one unique characteristic which is the chemical imbalance in the atmosphere due to biological activity. For example, when methane and oxygen are placed together, these gases will quickly react thus destroying each other. But these gases are plenty on earth, as biological activity keeps making them.
According to Catling, the lead author of the study, if we find something in equilibrium, then it is something dead or is not alive. Catling claims that finding something unusual will be the first sign of finding extraterrestrial life.
Scientists believe that the hunt for more biosignatures will continue in the coming years so that precisely spotting life on thousands of exoplanets will be easier.