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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Ocean currents swirl around North America (center left) and Greenland (upper right) in this data visualization created using NASA’s ECCO model. Advanced computing is helping oceanographers decipher hot spots of phytoplankton growth.NASA’s Scientific Visualization Studio As Greenland’s ice retreats, it’s fueling tiny ocean organisms. To test why, scientists turned to a computer model out of JPL and MIT that’s been called a laboratory in itself.
Runoff from Greenland’s ice sheet is kicking nutrients up from the ocean depths and boosting phytoplankton growth, a new NASA-supported study has found. Reporting in Nature Communications: Earth & Environment, the scientists used state-of-the art-computing to simulate marine life and physics colliding in one turbulent fjord. Oceanographers are keen to understand what drives the tiny plantlike organisms, which take up carbon dioxide and power the world’s fisheries.
Greenland’s mile-thick ice sheet is shedding some 293 billion tons (266 billion metric tons) of ice per year. During peak summer melt, more than 300,000 gallons (1,200 cubic meters) of fresh water drain into the sea every second from beneath Jakobshavn Glacier, also known as Sermeq Kujalleq,the most active glacier on the ice sheet. The waters meet and tumble hundreds of feet below the surface.
Teal-colored phytoplankton bloom off the Greenland coast in this satellite image captured in June 2024 by NASA’s PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) mission.NASA The meltwater plume is fresh and more buoyant than the surrounding saltwater. As it rises, scientists have hypothesized, it may be delivering nutrients like iron and nitrate — a key ingredient in fertilizer — to phytoplankton floating at the surface.
Researchers track these microscopic organisms because, though smaller by far than a pinhead, they’re titans of the ocean food web. Inhabiting every ocean from the tropics to the polar regions, they nourish krill and other grazers that, in turn, support larger animals, including fish and whales.
Previous work using NASA satellite data found that the rate of phytoplankton growth in Arctic waters surged 57% between 1998 and 2018 alone. An infusion of nitrate from the depths would be especially pivotal to Greenland’s phytoplankton in summer, after most nutrients been consumed by prior spring blooms. But the hypothesis has been hard to test along the coast, where the remote terrain and icebergs as big as city blocks complicate long-term observations.
“We were faced with this classic problem of trying to understand a system that is so remote and buried beneath ice,” said Dustin Carroll, an oceanographer at San José State University who is also affiliated with NASA’s Jet Propulsion Laboratory in Southern California. “We needed a gem of a computer model to help.”
Sea of Data
To re-create what was happening in the waters around Greenland’s most active glacier, the team harnessed a model of the ocean developed at JPL and the Massachusetts Institute of Technology in Cambridge. The model ingests nearly all available ocean measurements collected by sea- and satellite-based instruments over the past three decades. That amounts to billions of data points, from water temperature and salinity to pressure at the seafloor. The model is called Estimating the Circulation and Climate of the Ocean-Darwin (ECCO-Darwin for short).
Simulating “biology, chemistry, and physics coming together” in even one pocket along Greenland’s 27,000 miles (43,000 kilometers) of coastline is a massive math problem, noted lead author Michael Wood, a computational oceanographer at San José State University. To break it down, he said the team built a “model within a model within a model” to zoom in on the details of the fjord at the foot of the glacier.
Using supercomputers at NASA’s Ames Research Center in Silicon Valley, they calculated that deepwater nutrients buoyed upward by glacial runoff would be sufficient to boost summertime phytoplankton growth by 15 to 40% in the study area.
More Changes in Store
Could increased phytoplankton be a boon for Greenland’s marine animals and fisheries? Carroll said that untangling impacts to the ecosystem will take time. Melt on the Greenland ice sheet is projected to accelerate in coming decades, affecting everything from sea level and land vegetation to the saltiness of coastal waters.
“We reconstructed what’s happening in one key system, but there’s more than 250 such glaciers around Greenland,” Carroll said. He noted that the team plans to extend their simulations to the whole Greenland coast and beyond.
Some changes appear to be impacting the carbon cycle both positively and negatively: The team calculated how runoff from the glacier alters the temperature and chemistry of seawater in the fjord, making it less able to dissolve carbon dioxide. That loss is canceled out, however, by the bigger blooms of phytoplankton taking up more carbon dioxide from the air as they photosynthesize.
Wood added: “We didn’t build these tools for one specific application. Our approach is applicable to any region, from the Texas Gulf to Alaska. Like a Swiss Army knife, we can apply it to lots of different scenarios.”
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
Written by Sally Younger
2025-101
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Last Updated Aug 06, 2025 Related Terms
Earth Carbon Cycle Earth Science Ice & Glaciers Jet Propulsion Laboratory Oceans PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) Water on Earth Explore More
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Explore This Section Perseverance Home Mission Overview Rover Components Mars Rock Samples Where is Perseverance? Ingenuity Mars Helicopter Mission Updates Science Overview Objectives Instruments Highlights Exploration Goals News and Features Multimedia Perseverance Raw Images Images Videos Audio More Resources Mars Missions Mars Sample Return Mars Perseverance Rover Mars Curiosity Rover MAVEN Mars Reconnaissance Orbiter Mars Odyssey More Mars Missions Mars Home 2 min read
Feeling the Heat: Perseverance Looks for Evidence of Contact Metamorphism
NASA’s Mars Perseverance rover acquired this image of the boulders along the contact at Westport, using its Mastcam-Z Left Camera, one of a pair of cameras located high on the rover’s mast. The rover acquired the image on July 10, 2025 — Sol 1560, or Martian day 1,560 of the Mars 2020 mission — at the local mean solar time of 11:23:38. NASA/JPL-Caltech/ASU Written by Melissa Rice, Professor of Planetary Science at Western Washington University
Following a short break for the July 4th holiday, Perseverance drove westward to a site called “Westport,” where the clay-bearing “Krokodillen” unit meets an olivine-bearing rock formation. It is possible that the olivine-rich rocks are an intrusive igneous unit, meaning they could have formed when molten magma from deep within Mars got pushed upwards and cooled under the surface. If that’s the case, Westport could preserve a dramatic moment in Mars’ history when hot, molten material intruded into existing rock formations.
Those intrusive processes are common on Earth, and the heat of the intruding magma can fundamentally alter the surrounding geology through a process called “contact metamorphism.” The heat from the intrusion will “bake” nearby rocks, creating new minerals and potentially new environments for microbial life. Conversely, the intrusive rocks get rapidly “chilled” where they meet preexisting solid rock formations.
At Westport, Perseverance is looking for evidence that the Krokodillen rocks at the contact were baked, and that the olivine-bearing rocks at the contact were chilled. Images from the Mastcam-Z instrument reveal that the contact is littered with intriguing dark, rubbly rocks alongside lighter-toned, smooth boulders. Both rock types are proving challenging to study.
The dark fragments are too small and rough for Perseverance’s standard abrasion techniques, but the rover cleared off the surface of a rock called “Holyrood Bay” with its gas Dust Removal Tool (gDRT). Perseverance also tried to abrade a nearby boulder named “Drake’s Point,” but the rock shifted to the side, causing the abrasion to stop short. The science questions here are compelling enough, however, that Perseverance will keep trying to look within the rocks at this important boundary.
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By NASA
NASA Glenn Research Center’s Thermal Energy Conversion Branch team and the University of Leicester’s Space Nuclear Power team pose for a photo at the center in Cleveland following a successful test in January 2025.Credit: NASA/Jef Janis To explore the unknown in deep space, millions of miles away from Earth, it’s crucial for spacecraft to have ample power. NASA’s radioisotope power systems (RPS) are a viable option for these missions and have been used for over 60 years, including for the agency’s Voyager spacecraft and Perseverance Mars rover. These nuclear batteries provide long-term electrical power for spacecraft and science instruments using heat produced by the natural radioactive decay of radioisotopes. Now, NASA is testing a new type of RPS heat source fuel that could become an additional option for future long-duration journeys to extreme environments.
Historically, the radioisotope plutonium-238 (plutonium oxide) has been NASA’s RPS heat source fuel of choice, but americium-241 has been a source of interest for the past two decades in Europe. In January, the Thermal Energy Conversion Branch at NASA’s Glenn Research Center in Cleveland and the University of Leicester, based in the United Kingdom, partnered through an agreement to put this new option to the test.
One method to generate electricity from radioisotope heat sources is the free-piston Stirling convertor. This is a heat engine that converts thermal energy into electrical energy. However, instead of a crankshaft to extract power, pistons float freely within the engine. It could operate for decades continuously without wear, as it does not have piston rings or rotating bearings that will eventually wear out. Thus, a Stirling convertor could generate more energy, allowing more time for exploration in deep space. Researchers from the University of Leicester — who have been leaders in the development of americium RPS and heater units for more than 15 years — and NASA worked to test the capabilities of a Stirling generator testbed powered by two electrically heated americium-241 heat source simulators.
“The concept started as just a design, and we took it all the way to the prototype level: something close to a flight version of the generator,” said Salvatore Oriti, mechanical engineer at Glenn. “The more impressive part is how quickly and inexpensively we got it done, only made possible by a great synergy between the NASA and University of Leicester teams. We were on the same wavelength and shared the same mindset.”
Salvatore Oriti, mechanical engineer in the Thermal Energy Conversion Branch at NASA’s Glenn Research Center in Cleveland, adjusts the Stirling testbed in preparation for testing at the center in January 2025.Credit: NASA/Jef Janis The university provided the heat source simulators and generator housing. The heat source simulator is the exact size and shape of their real americium-241 heat source, but it uses embedded electric heaters to create an equivalent amount of heat to simulate the decay of americium fuel and therefore drive generator operation. The Stirling Research Lab at Glenn provided the test station, Stirling convertor hardware, and support equipment.
“A particular highlight of this (testbed) design is that it is capable of withstanding a failed Stirling convertor without a loss of electrical power,” said Hannah Sargeant, research fellow at the University of Leicester. “This feature was demonstrated successfully in the test campaign and highlights the robustness and reliability of an Americium-Radioisotope Stirling Generator for potential future spaceflight missions, including long-duration missions that could operate for many decades.”
The test proved the viability of an americium-fueled Stirling RPS, and performance and efficiency targets were successfully met. As for what’s next, the Glenn team is pursuing the next version of the testbed that will be lower mass, higher fidelity, and undergo further environmental testing.
“I was very pleased with how smoothly everything went,” Oriti said of the test results. “Usually in my experience, you don’t accomplish everything you set out to, but we did that and more. We plan to continue that level of success in the future.”
For more information on NASA’s RPS programs, visit:
https://science.nasa.gov/rps
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