The Value of Analog Research in the Search for Life

Abstract:

All we know about life and our understanding of its distribution throughout the Universe is based on our understanding of how life originated and evolved, and how it has persisted here on Earth. As we have refined our list of requirements for earth-like organisms and explored the limits of our biosphere, a variety of possible extraterrestrial habitats that could support life have emerged. Although our access to other potentially habitable worlds is limited, we continue to increase our understanding of the environmental conditions on bodies in our solar system which can inform our search for appropriate analogue sites. There is no perfect analogue for other planetary habitable environments on Earth. Earth is a planet with plate tectonics, a hydrological cycle, a thick atmosphere and stronger gravity than most candidate systems. Moreover, present day Earth is a verdant, interconnected system resulting from billions of years of biosphere evolution. Such differences pose a challenge to analogue research and in particular limit the interpretation of the environment under study in important ways. Earth’s extreme environments have been proposed as analogues of planetary environments. A common error is to assume if an environment is extreme or it is cold and dry it will make an excellent analogue site. The value of an analogue site is measured by a good assessment of the relevance of a site with rigorous attention to its Earth-based limitations is necessary and it will have different impacts depending on the question under study. Additionally, modern and ancient systems on earth can also be investigated in order to target a future search for as yet undetected terrestrial features and processes that preserve or indicate signs of past life. Despite any limitations, analogue research is essential and field research at these terrestrial sites represents a growing aspect of planetary science. Those relevant to the search for life are supported by NASA’s Planetary Science, Technology through Analog Research (PSTAR).