The next decade of planetary science and astrobiology holds tremendous promise. New research will expand our understanding of our solar system’s origins, how planets form and evolve, under what conditions life can survive, and where to find potentially habitable environments in our solar system and beyond. The decadal survey defines a set of key science questions that will serve as a critical foundation for the next decade of missions and research.
What were the initial conditions in the solar system? What processes led to the production of planetary building blocks, and what was the nature and evolution of these materials?
Learn more in Chapter 4.
How and when did the giant planets and their satellite systems originate, and did their orbits migrate early in their history? How and when did dwarf planets and cometary bodies orbiting beyond the giant planets form, and how were they affected by the early evolution of the solar system?
Learn more in Chapter 5.
How and when did the terrestrial planets, their moons, and the asteroids accrete, and what processes determined their initial properties? To what extent were outer solar system materials incorporated?
Learn more in Chapter 6.
How has the population of solar system bodies changed through time, and how has bombardment varied across the solar system? How have collisions affected the evolution of planetary bodies?
Learn more in Chapter 7.
How do the interiors of solid bodies evolve, and how is this evolution recorded in a body’s physical and chemical properties? How are solid surfaces shaped by subsurface, surface, and external processes?
Learn more in Chapter 8.
What establishes the properties and dynamics of solid body atmospheres and exospheres, and what governs material loss to space and exchange between the atmosphere and the surface and interior? Why did planetary climates evolve to their current varied states?
Learn more in Chapter 9.
What processes influence the structure, evolution, and dynamics of giant planet interiors, atmospheres, and magnetospheres?
Learn more in Chapter 10.
What processes and interactions establish the diverse properties of satellite and ring systems, and how do these systems interact with the host planet and the external environment?
Learn more in Chapter 11.
What conditions and processes led to the emergence and evolution of life on Earth, what is the range of possible metabolisms in the surface, subsurface and/or atmosphere, and how can this inform our understanding of the likelihood of life elsewhere?
Learn more in Chapter 12.
Where in the solar system do potentially habitable environments exist, what processes led to their formation, and how do planetary environments and habitable conditions co-evolve over time?
Learn more in Chapter 13.
Is there evidence of past or present life in the solar system beyond Earth and how do we detect it?
Learn more in Chapter 14.
What does our planetary system and its circumplanetary systems of satellites and rings reveal about exoplanetary systems, and what can circumstellar disks and exoplanetary systems teach us about the solar system?
Learn more in Chapter 15.
The decadal survey emphasizes the importance of balance across mission cost classes (including flagship, New Frontiers, and Discovery programs) when defining a mission portfolio to maximize overall scientific return.
The Lunar Discovery and Exploration Program (LDEP) supports industry partnerships and innovative approaches to accomplishing exploration and science goals, including the Commercial Lunar Payload Services (CLPS) program for lunar landing services. With NASA’s goal to send Artemis astronauts to the lunar surface within this decade, multiple research and technology development investments are required now to enable and optimize high-priority lunar science activities with humans at the Moon.
Recommendation: PSD should execute a strategic program to accomplish planetary science objectives for the Moon, with an organizational structure that aligns responsibility, authority, and accountability.
Recommendation: The advancement of high priority lunar science objectives, as defined by PSD based on inputs from this report and groups representing the scientific community, should be a key requirement of the Artemis human exploration program.
As human exploration advances into the solar system, it is essential that NASA’s science and human directorates work together to deliver ground-breaking science. The Endurance-A sample return mission, a medium-class robotic mission to collect samples from key lunar locations for later retrieval by Artemis astronauts, exemplifies this synergy. This mission would enable the highest priority lunar science not possible through the local collection of limited samples and could revolutionize our understanding of the Moon and the early history of the solar system.
Recommendation: Endurance-A should be implemented as a strategic medium-class mission as the highest priority of the Lunar Discovery and Exploration Program. Endurance-A would utilize CLPS to deliver the rover to the Moon, a long-range traverse to collect a substantial mass of high-value samples, and astronauts to return them to Earth.
Human exploration of space inspires our nation and the world while simultaneously benefiting our technology development, economic standing, and scientific knowledge. Human and robotic exploration of the solar system over the next decade and beyond will benefit from a logical, sustained, and science-focused approach. The decadal survey addresses the opportunities for science within the context of current human exploration plans and priorities, as well as areas of planetary science that can support human flight activities. Although humans may eventually travel to the far reaches of the solar system, the Moon and Mars are the most likely near-term, science-rich destinations, based on stated NASA and commercial exploration plans.
For this decade with a near-term plan for human exploration of the Moon and preparatory activities at Mars, the decadal survey emphasizes the importance of carefully crafted collaboration. A program of scientific exploration can be constructed this decade whereby science enables human exploration and human exploration enables science.
Learn more in Chapter 19.
Planetary defense is an international cooperative enterprise aimed at providing protection to the nations of the world from devastating asteroid and comet impacts. NASA, NSF, and other government agencies play a leading role in developing the capacity to understand the NEO hazard and build a long-term ability to counter a potential impact threat. A robust program of activities in the coming decade will enable the U.S. planetary defense community to forge detection, warning, and mitigation capabilities that will stand as a global example of how to shield society from a destructive yet preventable natural disaster.
Congressionally directed Near Earth Object (NEO) detectiongoals will be ideally advanced by NEO Surveyor, a dedicated, space-based mid-infrared survey telescope currently pending confirmation.
Recommendation: NASA should fully support the development, timely launch, and subsequent operation of NEO Surveyor to achieve the highest priority planetary defense NEO survey goals.
Advancing planetary defense will require assessment of mitigation techniques, as well as the ability to characterize newly identified hazardous objects. NASA’s DART mission, scheduled to impact the moonlet of the binary asteroid 65803 Didymos in 2022, will demonstrate one approach to asteroid deflection.
Recommendation: The highest priority planetary defense demonstration mission to follow DART and NEO Surveyor should be a rapid-response, flyby reconnaissance mission targeted to a challenging NEO, representative of the population of objects posing the highest probability of a destructive Earth impact (~50-to-100 m in diameter). Such a mission should assess the capabilities and limitations of flyby characterization methods to better prepare for a short-warning-time NEO threat.
The state of the profession (SoP) – including issues of diversity, equity, inclusivity, and accessibility – is central to the success of the planetary science enterprise. Ensuring broad access and participation is required to recruit, retain, and nurture the best talent, and to support continued American leadership in planetary science and astrobiology (PS&AB).
The committee applauds the hard-earned progress that has been made, most notably with respect to the entry and prominence of women in the field. However, much work remains to be done to address persistent and troubling issues of basic representation by race/ethnicity.
The decadal survey’s eight state of the profession recommendations address:
Equity and accountability require accurate and complete data about the SoP. There is an urgent need for data concerning the size, identity, and demographics of the PS&AB community; and workplace climate. Without such data, it cannot be known if the best available talent is being utilized, nor how involvement may be undermined by adverse experiences.
The committee recommends that the PSD adopt the view that bias can be both unintentional and pervasive, and provides actionable steps to assist NASA in identifying where bias exists and in removing it from its processes.
Engaging underrepresented communities at secondary and college levels to encourage and retain them along PS&AB career pathways is essential to creating and sustaining a diverse community.
Ensuring that all community members are treated with respect, developing and enforcing codes of conduct, and providing ombudsperson support to address issues is important for maintaining healthy and productive work environments.
Learn more in Chapter 16.
HIGHLIGHTS FROM THE PAST DECADE
New missions and data, advances in theory and modeling, telescopic observations, and laboratory experiments have led to amazing breakthroughs in planetary science and astrobiology over the past decade. Explore key discoveries from across the solar system below and learn more in Chapter 2.
Volcanism played a critical role in shaping Mercury’s surface, and permanently shadowed regions near Mercury’s poles hold abundant water ice.
Recent missions have revealed the surface and interior structure of the Moon in unprecedented detail, including newly discovered tectonic features and surface water ice in some permanently shadowed regions.
New evidence shows that Venus is likely geologically active today, and that surface conditions may have been habitable a billion years ago.
Mars is geologically active today with massive mid-latitude deposits of water ice and near-surface liquid water. Multiple types of habitable environments were widespread across ancient Mars.
Small Solar System Bodies
Inner solar system bodies provide new insight into planetary evolution and they possess a range of properties different from their outer solar system counterparts.
Giant Planet Systems
Saturn’s ring-moon system continues to change dramatically over time. Titan’s polar seas are deep and mostly methane.
Ocean Worlds and Dwarf Planets
Intermittent plumes of water vapor jet into space from Europa, and Enceladus is home to a potentially habitable water ocean. Pluto is unexpectedly geologically active, and brine deposits exist on the surface of Ceres.
The decadal survey identifies the most compelling science challenges and frontiers in planetary science and astrobiology and presents a comprehensive research strategy to advance the field in the next decade and beyond. This is the fourth decadal survey for planetary science conducted over the history of the National Academies, and like its predecessors, it will serve as a guide for scientists, decision makers, and agencies invested in the field.
The National Academies selected committee members in a process independent of sponsoring agencies after casting a wide net for participant recommendations, including an open call for nominations. Members of the steering committee were selected to cover as fully as possible the scientific scope of the survey and to form as representative a group of experts as possible in terms of individual, institutional, and geographical demographics. National Academies policies governing potential conflicts of interest by steering committee and panel members were strictly enforced. In particular, broad and open-minded thinkers were sought out as opposed to advocates for individual missions or subfields.
The information gathering and deliberative phases of the decadal survey were carefully coordinated. Members of the planetary science and astrobiology communities were invited to submit whitepapers to the survey, and these papers formed the foundation and starting point for all of the panel and working group deliberations. There were three separate calls for whitepapers over the course of the survey, focusing on science, programmatic and mission concepts, and the state of the profession. The survey received close to 600 whitepapers in total. Every whitepaper was assigned to and read by one or more of the decadal panels.
The study was led by a 19 member steering committee that was advised by 6 additional panels organized by planetary destination:
The decadal survey’s statement of task charged the committee with addressing the state of profession (SoP), including issues of diversity, equity, inclusion, and accessibility. This decadal survey presents a substantive discussion of these issues to signal their importance and urgency. The decadal survey steering committee–which included a social scientist to provide critical insight into these issues–engaged with available SoP data, white papers submitted to the decadal, invited speakers, robust internal discussions, as well as the best social, behavioral, and neuroscience evidence about the causes and outcomes that affect the quality of STEM professions. The decadal survey presents findings and recommendations that flow from this analysis with the goal of building a strong system of equity and accountability to nurture and sustain the field. As requested in the statement of task, these recommendations are actionable and intended to help NASA PSD bring the full force of its leadership and the engagement of the community to advance the profession as part of its scientific mission. Learn more about this effort in Chapter 16.
This decadal survey was sponsored by the National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF).
Background/Cover Images: Conrad Ziebland; ESO/L. Calçada; NASA; ESA/OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA/Gordan Ugarković; ESA/Hubble, M. Kornmesser; NASA/ESA/Hubble Heritage Team (STScI-AURA); MARUM−Zentrum für Marine Umweltwissenschaften, Universität Bremen; ESO/S. Brunier • Mars Exploration Section: NASA/ESA/JPL-Caltech; MOLA Science Team • Lunar Exploration Section: LPI • Human Exploration Section: NASA • Planetary Defense Section: NASA/Johns Hopkins, APL/Steve Gribben • Highlights Section: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington; NASA/GSFC/Arizona State University; JAXA/ISAS/DARTS/K. M. Gill/P. K. Byrne; ESA/DLR/FU-Berlin; NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute; NASA/JPL-Caltech; NASA/JPL/Space Science Institute