From: NASA Astrobiology
Posted: Thursday, May 28, 2020
Researchers supported in part by the NASA Astrobiology Program have proposed a new vocabulary for astrobiology research concerning the search for life beyond Earth.
The search for life in the Universe is one of NASA’s primary goals, and a key element of this endeavor is to understand what we are looking for. Life as we know it on Earth shows a remarkable amount of diversity, from microorganisms to multicellular animals. Yet every living organism on Earth today can be traced back through history to a single common ancestor. In this way, terran life provides only one example of biology.
When searching for life beyond Earth, ‘life as we know it’ serves as the starting point from which astrobiologists consider where and what to look for on other worlds among the stars. However, because Earth is the only example we have of an inhabited planet, the features that define ‘life as we know it’ are limited to this one example. This means that the search is inherently restricted by an Earth-centric view of what life is.
The authors equate this to a game of darts in which the effort is solely focused on hitting the bullseye. This bullseye is a narrow circle in a much broader field of possibilities, and is worth a lot of points. However, many of the other possibilities on the dart board are also incredibly valuable (in fact, the bullseye is not even the highest-scoring target on a dart board).
The new paper, published in the journal Life, outlines features of life that are specific to Earth, but that could also be broadly applicable in the search for ‘life as we don’t know it.’ The authors discuss qualities of life that we could look for on other worlds, where living systems might have evolved in a way that is completely different to the biology we see around us on our own planet.
In painting a more general picture of what life is, the researchers developed the term lyfe and outlined ‘four pillars’ of the term’s definition. These four pillars (dissipation, autocatalysis, homeostasis, and learning) can be used to identify any system that could be defined as living. Based on this criteria, the authors discuss Life (e.g. life as we know it on Earth) as a single instance of the broader phenomenon dubbed Lyfe. The terran example, Life, uses a set of molecules and reactions that are specific to our planet, but are not necessarily the same ‘toolbox’ that Lyfe could employ beyond Earth.
The team believes that this new classification system could be used to more clearly define the questions that shape astrobiology research, from origin of life studies to the search for habitable exoplanets. They pose the questions, are astrobiologists “developing a historical narrative to explain the origin of life (on Earth), or a universal narrative for the emergence of lyfe,” and are they “seeking signs of life specifically, or lyfe at large across the Universe.”
The idea that life could originate and evolve beyond the Earth in ways that are completely different than terran biology is not new. However, the authors propose that these four pillars of Lyfe “offer a novel perspective on what we consider to be a ‘living state,’ and could aid our understanding of what to look for in the search for life beyond Earth.”
The study, “Defining Lyfe in the Universe: From Three Privileged Functions to Four Pillars,” was published in Life. The work was supported by the Nexus for Exoplanet System Science (NExSS). NExSS is a NASA research coordination network supported in part by the NASA Astrobiology Program. This program element is shared between NASA’s Planetary Science Division (PSD) and the Astrophysics Division. This research is a critical part of NASA’s work to understand the Universe, advance human exploration, and inspire the next generation. As NASA’s Artemis program moves forward with human exploration of the Moon, the search for life on other worlds remains a top priority for the agency.
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