Taking Stock of the Solar System

As we turn over the calendar and start another year, NASA and the National Science Foundation (NSF) are also on the eve of receiving the Planetary Science and Astrobiology Decadal Survey for 2023–2032 from the National Academies of Sciences, Engineering, and Medicine (NASEM). This document, expected to be released in the spring of 2022, will lay out a vision for the next decade of solar system exploration, and help guide many of the activities conducted by the Planetary Science Division at NASA. I am excited to read what the Survey recommends, but before that, I want to take this opportunity to “take stock” and reflect on the current state of planetary science at NASA.

First and foremost, it is important to underline that this is an incredible time to be a planetary scientist — I thank my lucky stars often that I get to lead the Planetary Science Division (PSD) during this era of planetary exploration. Right now, we have 38 missions on our “fleet chart” (Fig. 1). Some of those are in development, some are in primary operations, and others are in their extended missions. More still are missions led by international agencies, on which we are proud to partner and provide mission hardware. These missions span the full breadth of the solar system — from ESA/JAXA’s BepiColombo mission currently on its way to Mercury (it performed the first of five Mercury flybys in 2021 and is due to enter Mercury orbit four years from now, in December 2025), all the way to the Kuiper belt with New Horizons, which is continuing its journey after encounters with the Pluto system and Arrokoth.

Graph of planetary fleet

Fig. 1. NASA’s Planetary Science Division mission fleet chart, December 2021. Credit: NASA.

Some of 2021’s biggest PSD highlights included changes and updates to this fleet chart. For instance, we celebrated two flawless launches of planetary missions in quick succession in the fall (Fig. 2). First, Lucy’s journey to Jupiter’s Trojan asteroids began with an early morning launch from Cape Canaveral in October 2021. Although the Lucy team is still working on an anomaly with one of the spacecraft’s solar arrays, we are confident they will find a good solution to enable Lucy’s 12-year magical mystery tour, during which it will conduct flybys of one main-belt and seven Trojan asteroids. Equipped with a suite of scientific instruments, Lucy will allow us to survey the diversity and gain new insights into the unique, never-before-explored population of asteroids that have been trapped in Jupiter’s orbit for billions of years. Just as Lucy the famous fossilized hominid skeleton (for the which the mission is named) provided fundamental knowledge of the evolution of our species, our Lucy mission is set to revolutionize our understanding of planetary origins and the formation of the solar system.

Lucy and DART mission launches

Fig. 2. Launch of Lucy from Cape Canaveral, October 16, 2021 (left), and launch of DART from Vandenberg Space Force Base, November 24, 2021 (right). Credit: NASA/Bill Ingalls.

Our second launch of 2021 was that of the Double Asteroid Redirection Test (DART) mission, which lifted off from Vandenberg Space Force Base right before Thanksgiving. DART is humanity’s first attempt to perceptibly alter the motion of an asteroid, as a test of the proposed planetary defense kinetic impact technique. DART is now headed for the Didymos binary asteroid system, which consists of the larger Didymos asteroid [about 780 meters (2560 feet) in diameter] and its small “moonlet” Dimorphos [about 161 meters (530 feet) in diameter]. On September 26, 2022, the spacecraft will autonomously direct itself to a head-on collision with Dimorphos. In doing so, we expect the speed of Dimorphos’ orbit around Didymos to slow slightly, but by enough that we will be able to detect the change in its orbital period from groundbased measurements (Fig. 3). Models suggest that the period will go from 11 hours and 55 minutes to approximately 11 hours and 45 minutes. Although we are not concerned that Didymos or Dimorphos pose any threat to Earth (nor will they after the DART impact), with this mission we are planning ahead by testing the technique and the technology now, so that we are prepared should we need to employ this kind of planetary defense approach at some point in the future. I will also emphasize that, as of now, no known asteroid is an impact threat to Earth at any time in the next century. Given the current incompleteness of the near-Earth object (NEO) catalog, however, an unpredicted event by an unknown asteroid could be discovered at any time. For this reason, I am pleased that the next planetary defense mission, NEO Surveyor, progressed to the next stage in its formulation in 2021. NEO Surveyor is designed to discover and characterize most of the potentially hazardous NEOs, i.e., those that are larger than 140 meters (459 feet). This mission will be another important piece in our planetary defense efforts.

DART mission

Fig. 3. Illustration of the effect of DART’s impact on the orbit of Dimorphos. Credit: NASA/Johns Hopkins APL.

Another highlight of 2021 was the selection of three new missions that will visit Venus over the next decade. Back in the spring, many in the community were surprised with the dual selection of two Venus missions as the next installments of the Discovery Program. Venus has had to wait a long time for a NASA mission, having not been visited by a targeted Venus probe since Magellan more than 30 years ago. The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) and Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy (VERITAS) missions, however, will lead a renaissance in Venus exploration science in the coming years. I am also delighted that these two missions will be joined by the ESA medium-class mission, EnVision, on which NASA will provide the synthetic aperture radar instrument (VenSAR) and will support some U.S. scientist involvement. Venus is compelling as a destination for many reasons and these missions will allow us specifically to make huge inroads into understanding how the evolutions of Earth and Venus diverged so greatly.

Of course, 2021 has been another year of perseverance, but also of ingenuity (Fig. 4)! The Mars2020 Perseverance Rover touched down safely in Jezero Crater back in February and has since been working to explore the region for signs of past microbial life. At the time of writing, the rover has collected seven samples (six rock samples and one atmospheric sample). These samples represent the first steps in the international endeavor of Mars sample return, through which the Mars2020 samples will be retrieved and returned to Earth in the coming years. Moreover, after the “Wright Brother’s moment” on April 19, 2021, when the Ingenuity helicopter made the first powered, controlled flight on another planet, Ingenuity completed its month-long technology demonstration with flying colors (pun intended). The helicopter continues to fly on a regular cadence and is now in an operational demonstration phase where it supports Perseverance planning and operations.

Mars 2020 Perseverance rover and Ingenuity helicopter

Fig. 4. The Mars2020 Perseverance rover and Ingenuity helicopter on the surface of Mars. Credit: NASA.

In addition to Mars sample return, we are excited about the other extraterrestrial materials that are on their way to, or newly arrived on, Earth. After its successful “touch and go” maneuver in 2020, OSIRIS-REx is now on its journey back to Earth, and it will deliver its precious sample of Bennu in September 2023. We are proud that we will be sharing part of the OSIRIS-REx sample with JAXA, and in reciprocation, JAXA has kindly allocated 10% of the Hayabusa-2 sample (from Ryugu) to NASA. We received this allocation of material at the Johnson Space Center in December, where it will be carefully curated and cataloged. We expect to announce sample availability in the coming months, with allocation to scientists in early summer 2022.

Looking ahead, many of our upcoming missions have made great progress in 2021, and I will mention a few (but not all) here. Psyche’s assembly, test, and launch operations (ATLO) phase is continuing, and we are excited for the mission’s launch in summer 2022. Likewise, the Europa Clipper project continues to make great strides toward its launch on a SpaceX Falcon Heavy in 2024; ATLO is set to begin this spring. For me, one of the most exciting elements in planetary exploration right now is the nascent Commercial Lunar Payload Services program, run out of the Exploration Science and Strategy Integration Office (ESSIO). I am eagerly awaiting the first of these launches in 2022, when Intuitive Machines and Astrobotic will be delivering NASA science and technology demonstration payloads to the lunar surface (at three separate sites:  Oceanus Procellarum, Lacus Mortis, and the south pole). Astrobotic will also be delivering our Volatiles Investigating Polar Exploration Rover (VIPER) to the lunar south pole in 2023. We now know that golf-cart-sized VIPER will explore the region close to Nobile Crater (with the precise landing site to be determined) during its 100-day mission. It will prospect for water ice and other potential resources so that we can learn more about the origin and distribution of water on the Moon and determine how to harvest lunar resources for future human exploration.

It is important to recognize that the work of PSD is not entirely focused around our mission activities. Indeed, our Research and Analysis (R&A) programs are the lifeblood that sustains our scientific community. I’ve therefore been pleased to see significant recent changes to the way we run some of our R&A programs, and I believe these changes will have a positive effect on the community going forward. Starting with ROSES-20, we began implementing a Dual-Anonymous Peer Review (DAPR) process for the review of proposals to some programs. After the success of the pilot year, in which we used DAPR in the Habitable Worlds proposal cycle, the process is now being implemented more widely in several of our programs (including the cross-divisional Exoplanets Research Program, all our Data Analysis Programs, and others). Although DAPR does require proposers to change the way they write proposals, feedback so far has been overwhelmingly positive. More than that, it is vitally important that we strive to always maintain a fair review process that is as unbiased as possible — DAPR is a critical part of that endeavor.

Another big change in PSD R&A in 2021 has been the start of a three-year trial of a “no due date” (NoDD), or rolling submission, approach. For many of our core research programs, rather than NASA-imposed deadlines for proposal submissions, we have adapted these programs so that proposals can be submitted on the proposers’ desired timeline. This means there does not need to be a rush to complete proposals, nor would proposers be unfairly penalized for accidentally missing a submission deadline. Instead, proposers can submit proposals when they believe they are at their best. Although it is too soon to measure and report the success of this initiative, I hope that it will bring a positive change for all.

In the October 2021 issue of this publication, I outlined some of the inclusion, diversity, equity, and accessibility (IDEA) initiatives we are working on at NASA, and especially within the Science Mission Directorate (SMD) and PSD. Under the remit of the new SMD-wide IDEA Working Group, we are working on a multitude of inward- and outward-facing activities that I know will make a difference, both in-house and in our wider science community. In addition to the plans I discussed previously, we are also starting a new SMD Bridge Program. This initiative is designed to boost diversity, equity, inclusion, and accessibility within the NASA workforce and within the U.S. science and engineering ecosystem. Funding for this program was included in the FY22 President’s Budget Request, and it will allow increased engagement and partnering between minority-serving institutions, other Ph.D.-granting universities, and NASA centers. The focus of the program will be on paid research and engineering studentships at participating institutions, to allow students to effectively transition from undergraduate studies into graduate schools and employment by NASA. SMD will be facilitating community-planning workshops that will allow this program to be collaboratively co-created with all stakeholders.

Before completing this stock-taking, I would be remiss if I didn’t discuss some of our amazing recent science results. After all, our exploration, our missions, and our curiosities are driven by science first and foremost. Results from InSight were published in a suite of three Science papers, which provided details on the depth and composition of Mars’ crust, mantle, and core. Specifically, these InSight results confirmed that the planet’s center is molten. The results also turned up a surprise — that the most significant “marsquakes” detected by InSight come from one area, known as Cerberus Fossae, which is a region volcanically active enough that lava may have flowed there in the last few million years. Curiously, however, no quakes have been detected from more prominent volcanic regions, like Tharsis.

Juno celebrated 10 years in space in 2021 and marked the occasion by entering its extended mission phase. During this new phase, the spacecraft will make a series of flybys of the jovian moons Ganymede, Io, and Europa — the first flyby of Ganymede occurred in June and was the first visit to this moon by a spacecraft in more than two decades (Fig. 5). The science results from Juno also continue to flow at an astounding speed. For example, a new map of Jupiter’s magnetic field is the most detailed ever, providing insights into the gas giant’s mysterious Great Blue Spot (a magnetic anomaly) at the planet’s equator. The Juno data indicate that a change in Jupiter’s magnetic field occurred during the time Juno has been in orbit, and that this spot is moving eastward at a rate of about 5 centimeters (2 inches) per second (meaning it would lap the planet in about 350 years). In contrast, the well-known Great Red Spot is drifting westward at a much more rapid pace (circling the planet in about 4.5 years). The new map also shows that Jupiter’s zonal winds (jet streams) are pulling the Great Blue Spot apart, meaning that these winds, which are measured at the surface of the planet, actually reach deep into the planet’s interior.


Fig. 5. First view of Ganymede in more than 20 years, taken during the Juno flyby on June 7, 2021. Credit: NASA/JPL/SwRI/MSSS.

On the astrobiology front, a very successful “Biosignature Standards of Evidence Workshop” was held in July 2021, with the focus on developing a generalized, progressive framework for robust biosignature assessment. This workshop is part of a larger effort to ensure that we, as a science community, are being responsible in our search for life elsewhere in the universe. An article, published in Nature in October, is a rallying cry to the community to ensure that we engage in an open dialogue about how to convey information in the diverse, complicated field of astrobiology and biosignature detection — a field that has a great potential to be sensationalized. The July workshop was therefore a direct response to this need. Hundreds of international participants attended the workshop, many of whom contributed to drafting the white paper that was a product of the meeting. This white paper was open for public comment during the fall, and the draft version can be read here. I am eager to read the final version and its findings and to receive the independent review of the white paper that is currently being conducted by NASEM’s Committee on Astrobiology and Planetary Sciences (CAPS).

As I close, I want to stress my sincere thanks to the whole planetary science community for their perseverance, passion, and patience as we have traversed these tiresome past two years. More than that, I cannot express enough how thankful we at NASA are for each individual scientist’s service to our work and to our community — whether that’s serving as a proposal reviewer, volunteering time to work with one of our Analysis/Assessment Groups, working as part of the Decadal Survey efforts, or contributing to another community need. Your time, your energy, and your expertise are truly appreciated. You are all a key part of our mission of exploring the unknown and inspiring the world around us.