seven long-term science goals
Understand the nature and distribution of habitable environments in the Universe.
A planet or planetary satellite is habitable if it can sustain life that originates there or if it sustains life that is carried to the object. The Astrobiology program seeks to expand our understanding of the most fundamental environmental requirements for habitability. Habitable environments must provide extended regions of liquid water, conditions favorable for the assembly of complex organic molecules, and energy sources to sustain metabolism. Habitability is not necessarily associated with a single specific environment; it can embrace a suite of environments that communicate through exchange of materials.
Life in the Solar System
Explore for past or present habitable environments, prebiotic chemistry and signs of life elsewhere in our Solar System.
The exploration for habitable environments, life and/or prebiotic chemistry in the Solar System directly links basic research in astrobiology to NASA missions. Because little is presently known about habitable environments within our Solar System, the distribution and nature of potentially habitable environments should be determined on Mars, Titan, Europa, and other promising objects. Although life elsewhere could have developed in ways different from life on Earth, our current knowledge of life and habitable environments serves as the starting point for our exploration strategy. Research in such widely divergent areas as planetary and Solar System evolution, the biology of extreme environments, and Precambrian paleontology has been instrumental in guiding NASA's search for evidence of life elsewhere in the Solar System.
Origins of Life
Understand how life emerges from cosmic and planetary precursors.
How life begins remains a fundamental unsolved mystery. The origin of life on Earth is likely to represent only one pathway among many along which life can emerge. Thus the universal principles must be understood that underlie not only the origins of life on Earth, but also the possible origins of life elsewhere. These principles will be sought by determining what raw materials of life can be produced by chemical evolution in space and on planets.
Earth’s Early Biosphere and its Environment
Understand how past life on Earth interacted with its changing planetary and Solar System environment.
We seek to understand how the planetary environment has influenced the evolution of life and how biological processes changed the environment. An improved knowledge of how life has altered diverse environments throughout Earth history will improve our ability to detect remnant biosignatures, even in cases where life has become extinct.
Evolution, Environments and Limits of Life
Understand the evolutionary mechanisms and environmental limits of life.
The diversity of life on Earth today is a result of the dynamic interplay between genetic opportunity, metabolic capability and environmental challenges. Life survives and sometimes thrives under what seem to be harsh conditions on Earth. For example, some microbes thrive at temperatures of 113°C. Others exist only in highly acidic environments or survive exposures to intense radiation. While all organisms are composed of nearly identical molecules, evolution has enabled such microbes to cope with this wide range of physical and chemical conditions. What are the features that enable one microbe to thrive under extreme conditions that are lethal to many others? An understanding of the tenacity and versatility of life on Earth, as well as an understanding of the molecular systems that some organisms utilize to survive such extremes, will provide a critical foundation for the search for life beyond Earth. These insights will help us to understand the molecular adaptations that define the physical and chemical limits for life on Earth. They will provide a baseline for developing predictions and hypotheses about life on other worlds.
Life’s Future on Earth and Beyond
Understand the principles that will shape the future of life, both on Earth and beyond.
Life on Earth is based upon networks of biochemical reactions that interact with the crust, oceans and atmosphere to maintain a biosphere that has been remarkably resilient to environmental challenges. These networks of metabolic reactions developed within self-organized microbial ecosystems that collectively responded to environmental changes in ways that apparently stabilized the biosphere. Viewing Earth's ecosystems in the context of astrobiology challenges us to consider how "resilient" life really is on a planetary scale.
Signatures of Life
Determine how to recognize signatures of life on other worlds and on early Earth.
Astrobiological exploration is founded upon the premise that signatures of life (biosignatures) encountered in space will be recognizable. A biosignature is an object, substance and/or pattern whose origin specifically requires a biological agent. Measurable attributes of life include its complex physical and chemical structures and also its utilization of free energy and the production of biomass and wastes; phenomena that can be sustained through self-replication and evolution.