NASA is at the helm of a new project searching for signs of extraterrestrial life among the 3,700 exoplanets discovered in the past 30 years.
The project specifically aims to identify biosignatures that may have been created by alien life forms at present or left behind by the extraterrestrials in the past. Biosignatures are any element, particles, molecules, or phenomenon that serves as proof of other beings hiding or still living in one of these exoplanets.
The project, called Nexus for Exoplanet Systems Science or NExSS, was formed three years ago with the ultimate goal of finding answers to question whether humans are alone in the universe. NASA builds an international team of scientists comprised of astrobiologists, planetary scientists, Earth scientists, heliophysicists, astrophysicists, chemists, and biologists to work on the project.
Initial results of the team's work were detailed in five separate papers published this month in the journal Astrobiology.
Ultimately, the papers all proposed ways to interpret the presence of most promising signs of life so that humans may distinguish another living world that might have been masquerading as a barren planet all along. They wanted to make way to pass the stage of theorizing to finally coming up with robust scientific proof.
"Given the massive implications of detecting an alien biosphere on an exoplanet, we're going to need all the tools in the toolbox to build up a sufficient level of confidence in our findings," said Theresa Fisher, a contributing author in one of the papers and a geological science graduate from Arizona State University's School of Earth and Space Exploration.
NExSS Scientists To Answer Question On Whether We Are Alone
The first five papers basically presented a framework where scientists categorized all scientific instruments that are needed to detect biosignatures and a list of potential biosignatures that scientists can observe. Through this, the scientists involved will then create a guidebook that will broadly classify the common characteristics of both the "living worlds" and the "non-living worlds."
The scientists aim to identify as many biosignatures as they can, especially those that are not found on Earth. This way, the scientists hoped to avoid being tricked into thinking that a planet is uninhabitable just because it does not have similar biosignatures with what was found on Earth.
"We have to be open to the possibility that life may arise in many contexts in a galaxy with so many diverse worlds — perhaps with purple-colored life instead of the familiar green-dominated life forms on Earth, for example," explained Mary Parenteau, a coauthor of one of the papers and an astrobiologist at NASA's Ames Research Center in Silicon Valley.
One of the papers was written by a team of scientists from Arizona State University and the University of California, Riverside. One important insight from the paper is for experts to observe Earth's biosphere, both at present and during geologic times. Edward Schwieterman, the lead author of the paper, said that the absence of oxygen in one planet, for example, is not enough basis to classify that planet as uninhabitable. He said life could exist in the absence of oxygen gas because that was the condition when early life began on Earth.
In a separate paper from a team from Arizona State University, the scientists argued that search for biosignatures should be extended beyond those of known life. Instead of focusing on whether a planet is habitable or not, the paper argued that experts should focus on the detectability of life on the planet. The paper said alien life may have needs that differ from what life on Earth requires.
Another paper from a team from the University of Washington provided a framework for evaluating the chemical composition of an exoplanet, its atmospheric conditions, the presence of oceans and continents, and its overall climate. The team provided a systematic way of rating a biosignature candidate from "very likely" to host life to "very unlikely" to produce life.
Two other papers discussed future scientific technologies that can be used to accurately detect biosignatures even from the most distant exoplanets.