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From page 382... ... 14 Question 11: Search for Life Elsewhere Is there evidence of past or present life in the solar system beyond Earth and how do we detect it? Building upon insights from terrestrial life and our understanding of the diversity of habitable environments elsewhere, as well as significant advancement in biosignature detection technologies, we are poised to conduct a rigorous, systematic search for life beyond Earth in the solar system. Read the entire page →
From page 383... ... FIGURE 14.1 Question 11. The search for life builds upon previous discoveries that span body interiors and surfaces to atmospheres and dynamic habitability (y-axis) Read the entire page →
From page 385... ... Q11.1a What Is the Organic Molecule Inventory of Habitable Environments Throughout the Solar System, Including Complex Organic Molecules That Can Serve as Prebiotic Building Blocks of Life? The first step to assessing the extent of organic chemical evolution in a habitable environment is understanding what organic molecules exist there now, and in what geochemical context. Read the entire page →
From page 386... ... molecules will react with or bind to another molecule of only a certain stereoisomeric conformation -- as well as the type and number of monomeric units in any macromolecules (i.e., polymerization) and any intermolecular interactions (i.e., quaternary structure) Read the entire page →
From page 387... ... If end-member cases of abiotic organic complexity and degree of organization can be established, they would serve as a metric against which habitable environments could be compared in the chemical evolution spectrum spanning fully abiotic to fully biotic. Any unambiguous life detection discovery will require that all plausible abiotic and prebiotic formation mechanisms for the potential biosignature(s) Read the entire page →
From page 389... ... life (NASEM 2019) Read the entire page →
From page 390... ... Q11.2c How Do the Physical and Chemical Properties and Processes in a Habitable World Affect the Survivability of Biosignatures? When considering the likelihood that a biosignature can be detected in a habitable environment, it is also important to consider how the physical and chemical conditions that make an environment habitable also act to modify, enhance, or erase evidence of inhabitation. Read the entire page →
From page 391... ... FIGURE 14.3 Question 11. A formal framework for interpretation of biosignature measurements would build on prior knowledge of biological and abiotic signatures and utilize data, environmental context and biological potential to construct a probabilistic model robust to false positives and false negatives. Read the entire page →
From page 392... ... ● Establish a comprehensive, standardized framework for evaluation of biosignatures, including the potential for abiosignatures, false positives, and false negatives, through community-level dialog and consensus, supported by laboratory/experimental and modeling/theoretical research as well as field work. Read the entire page →
From page 393... ... candidate biosignatures based on several key criteria (Q11.2) Read the entire page →
From page 394... ... results, where life could be "missed" for lack of the ability to detect or recognize it. These concepts apply equally to cases where life may have gone extinct, detectable through its imprint preserved over time (Q11.3b) Read the entire page →
From page 395... ... Q11.3b Are There Chemical, Morphological, or Other Biosignatures in Previously Habitable Environments in the Solar System? Mars witnessed a protracted period of habitable conditions early in its history, with relatively mild surface temperatures and widespread bodies of liquid water with physical and chemical conditions compatible with biology. Read the entire page →
From page 396... ... Both have been hypothesized to be able to harbor life as we don't know it (Lunine et al. 2020; Limaye et al. Read the entire page →
From page 397... ... observations or in samples returned to Earth, informed by laboratory/experimental and modeling/theoretical research as well as field work of currently habitable environments on Earth. ● Search for evidence of past life in environments beyond Earth that had a high biological potential in the past by looking for multiple, independent biosignatures with spacecraft in situ observations or in samples returned to Earth, informed by laboratory/experimental and modeling/theoretical research as well as field work of ancient life on Earth. Read the entire page →
From page 398... ... properties, emergence, prevalence, and workings at scales from microscopic to global could bring within reach a definition of life and a universal theory of biology. Since the onset of robotic exploration of the solar system, the knowledge gained via such exploration and concomitant advances in the understanding of what life requires, what constitutes evidence of life, and how to build instruments to search for it has poised humanity on the verge of finding and characterizing either life beyond Earth, or habitable worlds with no evidence of life. Read the entire page →
From page 399... ... Q11.4b How Do We Discriminate Between an Independent Origin of Life Elsewhere in the Solar System and a Shared Ancestry with Earth Life? The above alternative means by which biological structure and function may be achieved could be used to distinguish life that shares ancestry with Earth life (up to the point of a last universal common ancestor -- LUCA; Q9.1f) Read the entire page →
From page 400... ... Q11.4d How Have Life and Its Host World Co-Evolved? Determining the biochemical and metabolic characteristics of any extraterrestrial life would help us understand how it may have adapted to its environment, and perhaps the impact it has had on that environment from microscopic to global scales. Read the entire page →
From page 401... ... REFERENCES Altwegg, K., H Balsiger, A Read the entire page →
From page 402... ... Delitsky, M Read the entire page →
From page 403... ... Krissansen-Totton, J., R Buick, and D.C. Read the entire page →
From page 404... ... Postberg, F., N Khawaja, B Read the entire page →
From page 405... ... Zhang, J.A., and D.A. Paige. Read the entire page →
From page 406... ... Q12 PLATE: Artist's depiction of Kepler-186f, an Earth-sized planet orbiting a distant star in the habitable zone, discovered in 2014. Additional exoplanets can be seen closer to the star. Read the entire page →

From page 382...

... 14 Question 11: Search for Life Elsewhere Is there evidence of past or present life in the solar system beyond Earth and how do we detect it? Building upon insights from terrestrial life and our understanding of the diversity of habitable environments elsewhere, as well as significant advancement in biosignature detection technologies, we are poised to conduct a rigorous, systematic search for life beyond Earth in the solar system.