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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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By European Space Agency
With all eyes about to focus on the COP28 climate conference in Dubai, new scientific findings show, again, that the climate crisis is taking its toll on Antarctica – a continent, up to recently, thought better able to withstand the immediate effects of rising global temperatures.
Using satellite data, scientists have discovered that the ice shelf extending into the ocean from Cadman Glacier on the west Antarctic Peninsula collapsed, leaving the glacier exposed to unusually warm ocean water, which caused the glacier to accelerate and retreat rapidly.
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5 min read
NASA, Pacific Disaster Center Increase Landslide Hazard Awareness
Communities worldwide now have access to a powerful tool to increase their awareness of landslide hazards, thanks to NASA and the Pacific Disaster Center.
A humanitarian worker from USAID observes the impacts of a landslide. USAID deployed an elite Disaster Assistance Response Team on Nov. 17, 2020, to lead the U.S. response to Hurricanes Eta and Iota.USAID’s Bureau for Humanitarian Assistance After years of development and testing, NASA’s Landslide Hazard Assessment for Situational Awareness model (LHASA) has been integrated into the Pacific Disaster Center’s (PDC) multi-hazard monitoring, alerting, and decision-support platform, DisasterAWARE. LHASA allows researchers to map rainfall-triggered landslide hazards, giving DisasterAWARE users around the world a robust tool for identifying, tracking, and responding to these threats. The aim is to equip communities with timely and critical risk awareness that bolsters disaster resilience and safeguards lives and livelihoods.
Landslides cause thousands of deaths and billions of dollars in damage every year. Developing countries often bear disproportionate losses due to lack of access to hazard early warning systems and other resources for effective risk reduction and recovery. Reports from the United Nations Office for Disaster Risk Reduction emphasize that early warning systems and early action are among the most effective ways to decrease disaster-related deaths and losses.
The distribution of reported fatalities from 10,804 rainfall-triggered landslides in NASA’s Global Landslide Catalog (GLC) from 2007 to 2017. White dots represent incidents with zero reported fatalities and dots in the color scale from pink to red represent incidents in the range of 1-5000 fatalities. The NASA landslides team, based primarily out of NASA’s Goddard Space Flight Center, develops the Global Landslide Catalog and LHASA with support from NASA’s Disasters program. NASA Scientific Visualization Studio “Some local authorities develop their own systems to monitor landslide risk, but there isn’t a global model that works in the same way. That’s what defines LHASA: it works all the time and it covers most regions of the world,” says Robert Emberson, NASA Disasters associate program manager and a key member of the NASA landslides team. “Thanks to our collaboration with the Pacific Disaster Center, this powerful landslide technology is now even more accessible for the communities that need it most.”
LHASA uses a machine learning model that combines data on ground slope, soil moisture, snow, geological conditions, distance to faults, and the latest near real-time precipitation data from NASA’s IMERG product (part of the Global Precipitation Measurement mission). The model has been trained on a database of historical landslides and the conditions surrounding them, allowing it to recognize patterns that indicate a landslide is likely.
The result is a landslide “nowcast” – a map showing the potential of rainfall-triggered landslides occurring for any given region within the past day. This map of hazard likelihood can help agencies and officials rapidly assess areas where the current landslide risk is high. It can also give disaster response teams critical information on where a landslide may have occurred so they can investigate and deploy life-saving resources.
In 2021, a 7.2 magnitude earthquake struck Haiti, triggering a series of landslides across the country. Landslides can destroy infrastructure and impede the movement of people and life-saving aid. United Nations World Food Programme Partnering to Protect the Vulnerable
Generating landslide nowcasts is merely the first step. To be truly effective, vulnerable communities must receive the data in a way that is accessible and easy to integrate into existing disaster management plans. That’s where the Pacific Disaster Center comes in.
PDC is an applied research center managed by the University of Hawaii, and it shares NASA’s goal to reduce global disaster risk through innovative uses of science and technology. Its flagship DisasterAWARE software provides early warnings and risk assessment tools for 18 types of natural hazards and supports decision-making by a wide range of disaster management agencies, local governments, and humanitarian organizations. Prominent users include the International Federation of Red Cross and Red Crescent Societies (IFRC), the United Nations Office for the Coordination of Humanitarian Affairs (UN OCHA), and the World Food Programme (WFP).
“The close pairing of our organizations and use of PDC’s DisasterAWARE platform for early warning has been a special recipe for success in getting life-saving information into the hands of decision-makers and communities around the world,” said Chris Chiesa, PDC deputy executive director.
The collaboration with PDC brings NASA’s landslide tool to tens of thousands of existing DisasterAWARE users, dramatically increasing LHASA’s reach and effectiveness. Chiesa notes that teams in El Salvador, Honduras, and the Dominican Republic have already begun using these new capabilities to assess landslide hazards during the 2023 rainy season.
This screenshot from PDC’s DisasterAWARE Pro software shows LHASA landslide hazard probabilities for Myanmar in Sept. 2023. Red areas indicate the highest risk for landslide occurrence within the past three hours, while orange and yellow indicate lesser risk. Pacific Disaster Center PDC’s software ingests and interprets LHASA model data and generates maps of landslide risk severity. It then uses the data to generate landslide hazard alerts for a chosen region that the DisasterAWARE mobile app pushes to users. These alerts give communities critical information on potential hazards, enabling them to take protective measures.
DisasterAWARE also creates comprehensive regional risk reports that estimate the number of people and infrastructure exposed to a disaster – focusing specifically on things like bridges, roads, and hospitals that could complicate relief efforts when damaged. This information is critical for allowing decision-makers to effectively deploy resources to the areas that need them most.
DisasterAWARE landside risk report for Myanmar, showing estimated population, infrastructure and capital exposure to landslide risk, as well as the community’s needs. Pacific Disaster Center This effort between NASA and the PDC builds upon a history of fruitful cooperation between the organizations. In 2022, they deployed a NASA global flood modeling tool to enhance DisasterAWARE’s flood early-warning capabilities. They have also shared data and expertise during multiple disasters, including Hurricane Iota in 2020, the 2021 earthquake in Haiti, and the devastating August 2023 wildfires in Maui, PDC’s base of operations.
“The LHASA model is all open-source and leverages publicly available data from NASA and partners,” says Dalia Kirschbaum, lead of the NASA landslides team and director of Earth Sciences at NASA’s Goddard Space Flight Center. “This enables other researchers and disaster response communities to adapt the framework to regional or local applications and further awareness at scales relevant to their decision-making needs.” Kirschbaum and her team were recently awarded the prestigious NASA Software of the Year award for their work developing LHASA.
Last Updated Oct 26, 2023 Related Terms
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The maps above show sea levels in the Pacific Ocean during early October of 1997, 2015, and 2023, in the run up to El Niño events. Higher-than-average ocean heights appear red and white, and lower-than-average heights are in blue and purple. Sentinel-6 Michael Freilich is the latest satellite contributing to a 30-year sea level record that researchers are using to compare this year’s El Niño with those of the past.
Not all El Niño events are created equal. Their impacts vary widely, and satellites like the U.S.-European Sentinel-6 Michael Freilich help anticipate those impacts on a global scale by tracking changes in sea surface height in the Pacific Ocean.
Water expands as it warms, so sea levels tend to be higher in places with warmer water. El Niños are characterized by higher-than-normal sea levels and warmer-than-average ocean temperatures along the equatorial Pacific. These conditions can then propagate poleward along the western coasts of the Americas. El Niños can bring wetter conditions to the U.S. Southwest and drought to regions in the western Pacific, including Indonesia. This year’s El Niño is still developing, but researchers are looking to the recent past for clues as to how it is shaping up.
There have been two extreme El Niño events in the past 30 years: the first from 1997 to 1998 and the second from 2015 to 2016. Both caused shifts in global air and ocean temperatures, atmospheric wind and rainfall patterns, and sea level. The maps above show sea levels in the Pacific Ocean during early October of 1997, 2015, and 2023, with higher-than-average ocean heights in red and white, and lower-than-average heights in blue and purple. Sentinel-6 Michael Freilich captured the 2023 data, the TOPEX/Poseidon satellite collected data for the 1997 image, and Jason-2 gathered data for the 2015 map.
By October 1997 and 2015, large areas of the central and eastern Pacific had sea levels more than 7 inches (18 centimeters) higher than normal. This year, sea levels are about 2 or 3 inches (5 to 8 centimeters) higher than average and over a smaller area compared to the 1997 and 2015 events. Both of the past El Niños reached peak strength in late November or early December, so this year’s event may still intensify.
“Every El Niño is a little bit different,” said Josh Willis, Sentinel-6 Michael Freilich project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “This one seems modest compared to the big events, but it could still give us a wet winter here in the Southwest U.S. if conditions are right.”
More About the Mission
Launched in November 2020, Sentinel-6 Michael Freilich is named after former NASA Earth Science Division Director Michael Freilich. The satellite is one of two that compose the Copernicus Sentinel-6/Jason-CS (Continuity of Service) mission.
Sentinel-6/Jason-CS was jointly developed by ESA (European Space Agency), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), NASA, and the U.S. National Oceanic and Atmospheric Administration, with funding support from the European Commission and technical support on performance from the French space agency CNES (Centre National d’Études Spatiales).
To learn more about Sentinel-6 Michael Freilich, visit:
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Image credit: NASA
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