AliensExpanding the search for life in the universe

To advance the search for life in the universe, NASA should support research on a broader range of biosignatures and environments, and incorporate the field of astrobiology into all stages of future exploratory missions, says a new congressionally mandated report from the National Academies of Sciences, Engineering, and Medicine.

Astrobiology, the study of the origin, evolution, distribution, and future of life in the universe, is a rapidly changing field, especially in the years since the publication of NASA’s Astrobiology Strategy 2015. NAS says that recent scientific advances in the field now provide many opportunities to strengthen the role of astrobiology in NASA missions and to increase collaboration with other scientific fields and organizations. The report finds that these changes necessitate an updated science strategy for astrobiology.

The committee that authored the report found that the lines of evidence we use to look for current and past life on Earth and beyond, called biosignatures, needs expansion. An updated, more sophisticated catalog and framework will be important to enhance our ability to detect both life that might be similar to terrestrial life, and potential life that differs from life as we know it. The latter will be enabled by investigating novel “agnostic” biosignatures – signs of life that are not tied to a particular metabolism or molecular “blueprint,” or other characteristics of life as we currently know it.

A comprehensive framework could also aid in distinguishing between biosignatures and abiotic (non-living) phenomena, and improve understanding of the potential for biosignatures to be preserved (or not) over long planetary time-scales. The report highlights the need to include in situ detection of energy-starved or otherwise sparsely distributed life such as chemolithotrophic or rock-eating life. In particular, the report found that NASA should focus on research and exploration of possible life below the surface of a planet in light of recent advances that have demonstrated the breadth and diversity of life below Earth’s surface, the nature of fluids beneath the surface of Mars, and the likelihood of life-sustaining geological processes in planets and moons with subsurface oceans. A renewed focus on how to seek signs of subsurface life will inform astrobiology investigations of other rocky planets or moons, ocean or icy worlds, and beyond to exoplanets.

The report emphasizes the need for NASA to ramp up efforts in developing mission-ready life detection technologies to advance the search for life. For studies of life on planets outside of this solar system, the agency should implement technologies in near-term ground- and space-based direct imaging missions that can suppress the light from stars. The specialized measurements, equipment, and analysis required to take full advantage of space missions include some that exist outside of traditional space science fields, highlighting the need for interdisciplinary, non-traditional cooperation and collaboration with organizations outside of NASA, the report says.

So far, planning, implementation, and operations of planetary exploration missions with astrobiological objectives have tended to be more strongly defined by geological perspectives than by astrobiology-focused strategies.  The committee recommended the integration of astrobiology into all mission stages, from inception to development and operations. Collaboration with private, philanthropic, and international organizations, especially international space agencies, is also crucial to achieving the objectives of searching for life in the universe.

The committee also pointed out that adopting an interdisciplinary approach to astrobiology would produce a more complete picture of life on Earth as well as other planets. Integrating the physical, chemical, biological, geologic, planetary, and astrophysical sciences into the study of astrobiology will better show the relationship between life and its environment and how each changes, incorporating a new, dynamic view of habitability that includes consideration of multiple parameters. NASA should continue to actively seek new mechanisms to reduce the barriers to these potential collaborations, the report says.