Expanding the Definition of Life
I have always been in the camp of those that think that there is life elsewhere in the universe. Statistically, the universe is too vast, practically beyond human comprehension, for there not to be some form of life elsewhere. Those that have argued otherwise always come from the point of view that Earth and itsâ€™ biosphere is unique and have a definition of life that is completely Earth centric.
It was therefore with great interest that I read the report published last week by the National Research Council. This report suggested that life with an alternative biochemistry to that of life on Earth may be possible elsewhere in the universe. It went on to say that the search for extraterrestrial life should be broadened to consider this possibility and recommended research and missions in which the federal government should invest to increase our knowledge in this area.
Using the phrase â€œweird lifeâ€ the Council suggested that â€œthe fundamental requirements for life as we generally know it — a liquid water biosolvent, carbon-based metabolism, molecular system capable of evolution, and the ability to exchange energy with the environment — are not the only ways to support phenomena recognized as lifeâ€. The chair of the committee that published this recommendation, John Baross, professor of oceanography at the University of Washington said â€œ”Our investigation made clear that life is possible in forms different than those on Earth,”.
The assumption that â€œlifeâ€ should be defined by what we know about life on Earth has always impressed me as incredibly parochial and naÃ¯ve. Who are we to think that all life in the universe must be like us and what we know. The history of humanity and of science in particular is the constant expansion of knowledge that breaks through and expands traditional definitions of the physical world. 700 years ago, as we walked and rode horses across the earth, it was clear to every one that the world was flat. That was our perception and definition.
The interesting suggestion in the Councilsâ€™ report is that a narrow, earth-centric definition of life might well mean that we will completely miss finding life because we are looking for it through a lens that is too narrow in scope. To assume that life would utilize the same biochemical components as on Earth means that scientists have artificially limited the scope of where extraterrestrial life might be found. For example, to limit the search for life elsewhere to planets or moons that have water and temperature ranges similar to Earth may well be excluding large parts of the universe that do in fact have some other form of life. To again quote Baross: â€œIt is critical to know what to look for in the search for life in the solar system. The search so far has focused on Earth-like life because that’s all we know, but life that may have originated elsewhere could be unrecognizable compared with life here. Advances throughout the last decade in biology and biochemistry show that the basic requirements for life might not be as concrete as we thought.”
This is nothing less than a paradigm shift in terms of the definition and perception of life. Life on Earth may not be anything like life on other planets or moons in the Universe. Life could be anywhere and could take any shape and have a completely different biochemical composition than life as we know it. This means that future space missions must increase the breadth of exploration for extraterrestrial life. The report from the Council made a number of suggestions along these lines. Since this report was sponsored by NASA, I can only hope that it will be used to expand the vision of space exploration. While it is important to continually search for other places than Earth that might be hospitable for human life, it is even more important to look for life as we might not know it.