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From page 367... ... 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 on 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.1 Four hundred years after Galileo revolutionized our understanding of our place in the universe, ours could realistically be the generation that triggers another scientific revolution, this time in biology. Read the entire page →
From page 368... ... 368 ORIGINS, WORLDS, AND LIFE FIGURE 14-1 The search for life builds on previous discoveries that span body interiors and surfaces to atmospheres and dynamic habitability (vertical axis) Read the entire page →
From page 369... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 369 Aerosols/hazes/ clouds Regolith/sediments/ ice/permafrost Deep aquifers/ice FIGURE 14-2 Target environments and possible architectures of missions to search for life on other planetary bodies of the solar system. Left: Mission architectures to rocky planets and bodies with an atmosphere include (but are not limited to) Read the entire page →
From page 370... ... 370 ORIGINS, WORLDS, AND LIFE identified. Laboratory experiments designed to simulate the conditions and processes that occur in extraterrestrial material environments, such as cosmic ice irradiation and low-temperature photochemistry and geochemistry, are an important complement to the characterization of astromaterials (Hoehler et al. Read the entire page →
From page 371... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 371 but incomplete (Q10.4) Read the entire page →
From page 372... ... 372 ORIGINS, WORLDS, AND LIFE Q11.1c What Are the Relevant Chemical Pathways That Can Lead from Prebiotic Chemistry to Biochemistry, and How Does That Transition Depend on the Geochemical State of the Environment? Chemical pathways (i.e., links of chemical reactions) Read the entire page →
From page 373... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 373 reliability, detectability, and survivability (Meadows 2017; Meadows et al. Read the entire page →
From page 374... ... 374 ORIGINS, WORLDS, AND LIFE Q11.2b What Are the Relationships Between the Physical and Chemical Properties and Processes Operating in a Habitable Environment and the Potential Amount of Biomass That Might Be Present? How Might This Drive the Detectability of Any Biosignatures Present? Read the entire page →
From page 375... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 375 produced it, and the environment(s) in which the signature(s) Read the entire page →
From page 376... ... 376 ORIGINS, WORLDS, AND LIFE provide a more rigorous standard of proof. In addition, such frameworks can help identify sets of measurements that together discriminate between a biotic or abiotic origin for potential biosignatures with high statistical significance (NASEM 2019) Read the entire page →
From page 377... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 377 FIGURE 14-4 The search for life has been revolutionized in the past decades by pivotal discoveries such as the identification of what is now recognized as a third branch in the tree of life (Archaea) and confirmation of subsurface liquid water oceans within several moons of Jupiter and Saturn. Read the entire page →
From page 378... ... 378 ORIGINS, WORLDS, AND LIFE FIGURE 14-5 To provide evidence of life above the threshold established by abiotic processes in a given environment, multiple independent biosignatures (B) are needed, as well as a thorough understanding of the physicochemical setting (C) Read the entire page →
From page 379... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 379 FIGURE 14-6 Examples of instruments that can be used to search for chemical/molecular biosignatures, organized by their range of detection limits and sample processing requirements. Note that sample preconcentration can improve detection limits for some instruments. Read the entire page →
From page 380... ... 380 ORIGINS, WORLDS, AND LIFE metabolic biosignatures (which would indicate organisms that are alive today) may no longer be present, evidence of past life in the returned samples can be ascertained from chemical and morphological fingerprints left behind. Read the entire page →
From page 381... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 381 Q11.3d If We Do Not Find Evidence of Life in a Habitable Environment, What Would It Take to Convince Ourselves That There Truly Is or Was No Life Present There, Rather Than Possibly Not Having Detected It (a False Negative) Read the entire page →
From page 382... ... 382 ORIGINS, WORLDS, AND LIFE Q11.4 LIFE CHARACTERIZATION: WHAT IS THE NATURE OF LIFE ELSEWHERE, IF IT EXISTS? With terrestrial life as the sole example, biology is unlikely to evolve into a universal science in the same way as physics, chemistry, and geology have evolved with the respective advent of telescopic astronomy (17th century) Read the entire page →
From page 383... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 383 Q11.4a How Might Comparative Biology Be Implemented on a Small Sample Size (N = 2) If Evidence of Life Is Discovered Elsewhere in the Solar System? Read the entire page →
From page 384... ... 384 ORIGINS, WORLDS, AND LIFE that would be favorable or challenging to prebiotic chemical evolution (e.g., stability, longevity, energy supply, and dilution) , and the scarcity of early Archaean geologic and fossil records limits our capacity to constrain the actual environmental setting where life could have begun on our planet. Read the entire page →
From page 385... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 385 • Develop viable solutions to technical challenges for curation of samples to be returned from Mars and ocean worlds that will preserve their scientific integrity, including biosafe curation coupled (for ocean worlds) with cold conditions. Read the entire page →
From page 386... ... 386 ORIGINS, WORLDS, AND LIFE Des Marais, D.J., J.A. Read the entire page →
From page 387... ... QUESTION 11: SEARCH FOR LIFE ELSEWHERE 387 McCord, T.B., R.W. Carlson, W.D. Read the entire page →
From page 388... ... 388 ORIGINS, WORLDS, AND LIFE Vago, J.L., F Westall, Pasteur Instrument Teams, Landing Site Selection Working Group, et al. Read the entire page →
From page 390... ... Q12 PLATE: Artist's depiction of Kepler-186f, an Earth-size 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 367...

... 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 on 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.1 Four hundred years after Galileo revolutionized our understanding of our place in the universe, ours could realistically be the generation that triggers another scientific revolution, this time in biology.