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NASA/Aubrey Gemignani The Moon, left, Saturn, upper right, and Jupiter, lower right, are seen after sunset from Washington, DC, on Dec. 17, 2020. The two planets drew closer to each other in the sky as they headed towards a “great conjunction” on Dec. 21, where the two giant planets appeared a tenth of a degree apart. View and download the full image here.
See skywatching highlights, including meteor, asteroid, and planet sightings in What’s Up for Dec. 2023.
Image Credit: NASA/Aubrey Gemignani
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7 Min Read Digging Deeper to Find Life on Ocean Worlds
Conceptual image of a cryobot breaching into the ocean of Europa and searching for signs of life. Credits:
In February 2023, researchers from around the country gathered at a NASA-sponsored workshop to discuss the latest developments and a roadmap for a cryobot mission concept to drill through the icy crusts of Europa and Enceladus and search for life.
“Follow the water” has been the mantra of the astrobiology community in search of alien life in the universe. Water is a fundamental building block of all terrestrial life as we know it and—as discovered by various space missions—water is abundant throughout the solar system, and perhaps, the universe. Ancient eroded features on Mars show clear evidence of a wet history, and the ongoing quest of the Perseverance rover aims to uncover clues as to whether or not Mars once hosted a population of microbes. However, there is only so much we can learn from the fossil record. To truly understand the nature of possible alien life, we must directly investigate the source—the liquid water.
Enter “Ocean Worlds.” Over the past two decades, scientists have discovered that a vast number of icy moons orbit the outer giant planets in our solar system. Many of these moons show strong evidence for harboring global oceans beneath their icy crusts. In fact, these moons likely have far more liquid water than all of Earth’s oceans combined, and some may even have the right conditions to foster life. Two moons, in particular, have captured the imaginations of astrobiologists due to their amenable conditions for life and their relative ease of interrogation: Jupiter’s moon, Europa and Saturn’s moon, Enceladus. Both show strong evidence of a global subsurface ocean beneath a kilometers-thick water-ice crust—but how can we access this liquid water?
Various concepts for ocean access have been investigated over the past decades, ranging from robots that descend through crevasses to drills of varying types. One concept that has emerged as a leading candidate is the cryobot. A cryobot is a self-contained cylindrical probe that uses heat to melt the ice beneath it. The melted water then flows around the probe before refreezing behind it. Thermal ice drilling is so simple and effective that it has become a common tool for studying terrestrial glaciers and ice sheets. But how can we translate this technology to a system that can penetrate planetary icy crusts, which are colder, thicker, and more uncertain?
This dilemma has been a core focus of researchers—many of whom are supported by NASA’s Scientific Exploration Subsurface Access Mechanism for Europa (SESAME) and Concepts for Ocean worlds Life Detection Technology (COLDTech) programs—for the past several years. In February 2023, NASA’s Planetary Exploration Science Technology Office (PESTO) convened a workshop at the California Institute of Technology, which brought together nearly 40 top researchers from diverse fields and institutions around the country to discuss progress in maturing this technology and to assess the challenges that remain. Recent studies have made significant progress in refining our understanding of the ice shell environment, detailing a mission architecture, and maturing critical subsystems and technologies. In particular, workshop participants identified four key subsystems that drive the roadmap for developing a flight-ready architecture: the power, thermal, mobility, and communication subsystems.
Conceptual image of the Cryobot mission profile. A lander deploys a nuclear-powered probe, which melts through the ice shell to access the ocean below. A tether and wireless transceivers are deployed behind the probe during its descent for communication. Credit: NASA/JPL-Caltech First, the heart of a cryobot is a nuclear power system that generates the sustained heat required to melt through kilometers of ice. Various nuclear power systems that could suit a cryobot system have been identified, including the familiar Radioisotope Power Systems (RPS) that have powered many deep-space missions, and fission reactors that may be developed in the coming years. Two key constraints that drive the power system design are: (1) sufficient total power and density to facilitate efficient melting (about 10 kW), and (2) integration within a structural vessel to protect the power system from the high pressures of the deep ocean. These challenges are both solvable and have some historical precedent: NASA’s Cassini mission had a 14 kW thermal power system, and several Radioisotope Thermoelectric Generators (RTGs) were deployed to the bottom of the ocean in the 1960s and 1970s as power sources for navigation beacons, which operated in comparable pressures to the Europan ocean. However, a cryobot power system will require a concerted effort and close collaboration with the Department of Energy throughout the maturation of the mission concept.
Second, a thermal management system is required to manage the heat produced by the onboard nuclear power system, maintain safe internal temperatures, and distribute heat to the environment for efficient performance. This system requires two independent pumped fluid circuits: one that circulates an internal working fluid through channels embedded in the skin and another that circulates melted ice water with the surounding environment. Some of these technologies have been demonstrated at reduced and full scale, but more work is needed to validate performance at the range of ice conditions expected in the outer solar system.
In addition, the icy shells of Europa and Enceladus will contain impurities such as dust and salt, which, when sufficiently concentrated, may require auxilliary systems to penetrate. A combination of “water jetting” and mechanical cutting has been demonstrated to be effective at clearing debris ranging from fine particulate to solid blocks of salt from beneath the probe. Some impurities such as larger rocks, voids, or water bodies may remain impenetrable, requiring the cryobot to incorporate a downward-looking mapping sensor and steering mechanism—both of which have been demonstrated in terrestrial prototypes, though not yet in an integrated system. High-priority future work includes a more rigorous and probabilistic definition of the icy environments to quantify the likelihood of potential mobility hazards, and an integrated demonstration of hazard mitigation systems on a flight-like cryobot system. Europa Clipper will also provide key observations to constrain the prevalence and characteristics of hazards for a cryobot.
Finally, a cryobot mission requires a robust and redundant communication link through the ice shell to enable the lander to relay data to an orbiting relay asset or directly to Earth. Fiber optic cables are the industry standard for communicating with terrestrial melt probes and deep-sea vehicles, but require careful validation for deployment through ice shells, which are active. The movement of ice in these shells could break the cable. A team led by Dr. Kate Craft at the Johns Hopkins Applied Physics Laboratory has been investigating the propensity of tethers embedded in ice to break during ice-shear events, as well as methods to mitigate such breakage. While preliminary results from this study are highly encouraging, other teams are exploring wireless techniques for communicating through the ice, including radio frequency, acoustic, and magnetic transceivers. These communication systems must be integrated onto the aft end of the probe and depoyed during its descent. Current projects funded under the NASA COLDTech program are taking the first steps toward addressing key risks for the communications system. Future work must validate performance across a broader range of conditions and demonstrate integration on a cryobot.
While the power, thermal, mobility, and communication subsystems took center stage, workshop participants also discussed other key systems and technologies that will require maturation to enable a cryobot mission. These topics include an integrated instrument suite with accommodations for liquid sampling and outward-facing apertures, planetary protection and sterilization strategies, materials selection for corrosion mitigation, ice-anchoring mechanisms, and autonomy. However, none of these technologies were identified as major risks or challenges in the cryobot mission concept roadmap.
Overall, the consensus finding of workshop participants was that this mission concept remains feasible, scientifically compelling, and the most plausible near-term way to directly search for life in situ on an ocean world. Continued support would allow scientists and engineers to make even further progress toward readying cryobots for future mission opportunities. The potential for the direct detection of life on another world seems more possible than ever.
This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).
Dr. Benjamin Hockman, Jet Propulsion Laboratory, California Institute of Technology
NASA’s Planetary Exploration Science Technology Office (PESTO)
Last Updated Dec 05, 2023 Related Terms
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Architecture Concept Review attendees listen to welcome remarks from NASA leadership on Nov. 14, 2023, at NASA’s Kennedy Space Center in Florida. Attendees included representatives from all of NASA’s centers, leaders from all of NASA’s mission directorates, various technical authorities, and other stakeholders across the agency. NASA/Kim Shifflett NASA hosted its second annual Architecture Concept Review in mid-November, bringing together leaders from across the agency to discuss progress on and updates to NASA’s Moon to Mars architecture since NASA released outcomes from its first such review in April.
As NASA builds a blueprint for human exploration throughout the solar system for the benefit of humanity, the agency has established the internal Architecture Concept Review process to help align NASA’s Moon to Mars exploration strategy and codify the supporting architecture through robust analysis. Through this evolutionary process, NASA continuously updates its roadmap for crewed exploration, setting humanity on a path to the Moon, Mars, and beyond.
NASA leadership gives opening remarks at the review. From left to right: Casey Swails, deputy associate administrator; Catherine Koerner, deputy associate administrator for the Exploration Systems Development Mission Directorate; Jim Free, associate administrator for the Exploration Systems Development Mission Directorate; and Pam Melroy, deputy administrator. NASA/Kim Shifflett “Our yearly strategic analysis cycle informs architecture decisions by identifying technology gaps, performing trade studies, and soliciting feedback from industry, academia, and the international community,” said Catherine Koerner, deputy associate administrator for NASA’s Exploration Systems Development Mission Directorate. “This year’s review focused on identifying the foundational decisions needed for a crewed mission to Mars and adding more detail to how we break down our objectives for long-term lunar exploration into specific architectural elements.”
During the review, NASA also began to define potentially viable and affordable opportunities for new programs and projects that close capability gaps.
NASA will share the results of this year’s Architecture Concept Review cycle early next year. This will include an update to the agency’s Architecture Definition Document and associated white papers, which provide additional detail on results from this year’s strategic analysis cycle.
Both the updated Architecture Definition Document and white papers will be made available on NASA’s Moon to Mars architecture webpages.
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Google’s ‘A Passage of Water’ Brings NASA’s Water Data to Life
As part of the long-standing partnership between NASA and Google, NASA worked with Google Arts & Culture and artist Yiyun Kang to create an interactive digital experience around global freshwater resources titled “A Passage of Water.” This immersive experience leverages data from the Gravity Recovery and Climate Experiment (GRACE) satellites and new high-resolution data from the Surface Water and Ocean Topography (SWOT) mission to illustrate how climate change is impacting Earth’s water cycle.
A digital version of “A Passage of Water” will be released online on Thursday, Nov. 30, ahead of the beginning of the United Nations’ Climate Change Conference of Parties (COP 28) in Dubai, United Arab Emirates. Google also will host a physical installation of the visualization project in the Blue Zone at COP 28.
“NASA is the U.S. space agency that provides end-to-end research about our home planet, and it is our job to inform the world about what we learn,” said Kate Calvin, NASA’s chief scientist and senior climate advisor in Washington. “Highlighting our Earth science data in the installation of ‘A Passage of Water’ is a unique way to share information, in a digestible way, around the important connection between climate change and the Earth’s water cycle.”
The international Surface Water and Ocean Topography (SWOT) satellite, as shown in this illustration, is the first global mission surveying Earth’s surface water. SWOT’s high-resolution data helps scientists measure how Earth’s bodies of water change overtime. Credit: CNES. For six decades, NASA has been collecting data on Earth’s land, water, air, and climate. This data is used to inform decision-makers on ways to mitigate, adapt and respond to climate change. All of NASA’s Earth science data is available for scientists and the public to access in a variety of ways.
“NASA studies our home planet and its interconnected systems more than any other planet in our universe,” said Karen St. Germain, director of NASA’s Earth Science Division. “’A Passage of Water’ provides an opportunity to highlight the public availability of SWOT data and other NASA Earth science data to tell meaningful stories, improve awareness, and help everyday people who have to make real decisions in their homes, businesses, and communities.”
A collaboration between NASA and the French space agency CNES (Centre National d’Études Spatiales), SWOT is measuring the height of nearly all water on Earth’s surface, providing one of the most detailed, comprehensive views yet of the planet’s freshwater bodies. SWOT provides insights into how the ocean influences climate change and how a warming world affects lakes, rivers, and reservoirs.
NASA studies our home planet and its interconnected systems more than any other planet in our universe.
Karen St. Germain
Director, NASA’s Earth Science Division
“The detail that SWOT is providing on the world’s oceans and fresh water is game-changing. We’re only just getting started with respect to data from this satellite and I’m looking forward to seeing where the information takes us,” said Ben Hamlington, a research scientist at NASA’s Jet Propulsion Laboratory in Southern California.
The Google project also uses data from the GRACE and GRACE Follow-On missions –the former is a joint effort between NASA and the German Aerospace Center (DLR), while the latter is a collaboration between NASA and the German Research Centre for Geosciences (GFZ). GRACE tracked localized changes to Earth’s mass distribution, caused by phenomena including the movement of water across the planet from 2002 to 2017. GRACE-FO came online in 2018 and is currently in operation.
As with GRACE before it, the GRACE-FO mission monitors changes in ice sheets and glaciers, near-surface and underground water storage, the amount of water in large lakes and rivers, as well as changes in sea level and ocean currents, providing an integrated view of how Earth’s water cycle and energy balance are evolving.
“A Passage of Water” is the most recent digital experience created under NASA’s Space Act Agreement with Google, with resulting content to be made widely available to the public free of charge on Google’s web platforms. This collaboration is part of a six-project agreement series that aims to share NASA’s content with audiences in new and engaging ways.
Learn more about SWOT, GRACE, GRACE-FO, and NASA’s Earth Science missions at:
To learn more about NASA Partnerships, visit:
Last Updated Nov 30, 2023 Editor Contact Related Terms
Earth GRACE (Gravity Recovery And Climate Experiment) GRACE-FO (Gravity Recovery and Climate Experiment Follow-on) SWOT (Surface Water and Ocean Topography) Water on Earth Keep Exploring Discover More Topics From NASA
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA completed a full duration, 650-second hot fire of the RS-25 certification engine Nov. 29, continuing a critical test series to support future SLS (Space Launch System) missions to deep space as NASA explores the secrets of the universe for the benefit of all. Danny Nowlin NASA completed a full duration, 650-second hot fire of the RS-25 certification engine Nov. 29, continuing a critical test series to support future SLS (Space Launch System) missions to deep space as NASA explores the secrets of the universe for the benefit of all. Danny Nowlin NASA completed a full duration, 650-second hot fire of the RS-25 certification engine Nov. 29, continuing a critical test series to support future SLS (Space Launch System) missions to deep space as NASA explores the secrets of the universe for the benefit of all. Danny Nowlin NASA conducted the third RS-25 engine hot fire in a critical 12-test certification series Nov. 29, demonstrating a key capability necessary for flight of the SLS (Space Launch System) rocket during Artemis missions to the Moon and beyond.
NASA is conducting the series of tests to certify new manufacturing processes for producing RS-25 engines for future deep space missions, beginning with Artemis V. Aerojet Rocketdyne, an L3Harris Technologies Company and lead engines contractor for the SLS rocket, is incorporating new manufacturing techniques and processes, such as 3D printing, in production of new RS-25 engines.
Crews gimbaled, or pivoted, the RS-25 engine around a central point during the almost 11-minute (650 seconds) hot fire on the Fred Haise Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The gimbaling technique is used to control and stabilize SLS as it reaches orbit.
During the Nov. 29 test, operators also pushed the engine beyond any parameters it might experience during flight to provide a margin of operational safety. The 650-second test exceeded the 500 seconds RS-25 engines must operate to help power SLS to space. The RS-25 engine also was fired to 113% power level, exceeding the 111% level needed to lift SLS to orbit.
The ongoing series will stretch into 2024 as NASA continues its mission to return humans to the lunar surface to establish a long-term presence for scientific discovery and to prepare for human missions to Mars.
Four RS-25 engines fire simultaneously to generate a combined 1.6 million pounds of thrust at launch and 2 million pounds of thrust during ascent to help power each SLS flight. NASA and Aerojet Rocketdyne modified 16 holdover space shuttle main engines, all proven flightworthy at NASA Stennis, for Artemis missions I through IV.
Every new RS-25 engine that will help power SLS also will be tested at NASA Stennis. RS-25 tests at the site are conducted by a combined team of NASA, Aerojet Rocketdyne, and Syncom Space Services operators. Syncom Space Services is the prime contractor for Stennis facilities and operations.
Stay connected with the mission on social media, and let people know you’re following it on X, Facebook, and Instagram using the hashtags #Artemis, #NASAStennis, #SLS. Follow and tag these accounts:
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Last Updated Nov 29, 2023 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.email@example.com / (228) 688-3333LocationStennis Space Center Related Terms
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