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Keeping track of spacecraft as Earth’s water alters its spin
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By NASA
Scientists have hypothesized since the 1960s that the Sun is a source of ingredients that form water on the Moon. When a stream of charged particles known as the solar wind smashes into the lunar surface, the idea goes, it triggers a chemical reaction that could make water molecules.
Now, in the most realistic lab simulation of this process yet, NASA-led researchers have confirmed this prediction.
The finding, researchers wrote in a March 17 paper in JGR Planets, has implications for NASA’s Artemis astronaut operations at the Moon’s South Pole. A critical resource for exploration, much of the water on the Moon is thought to be frozen in permanently shadowed regions at the poles.
“The exciting thing here is that with only lunar soil and a basic ingredient from the Sun, which is always spitting out hydrogen, there’s a possibility of creating water,” Li Hsia Yeo, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s incredible to think about,” said Yeo, who led the study.
Solar wind flows constantly from the Sun. It’s made largely of protons, which are nuclei of hydrogen atoms that have lost their electrons. Traveling at more than one million miles per hour, the solar wind bathes the entire solar system. We see evidence of it on Earth when it lights up our sky in auroral light shows.
Computer-processed data of the solar wind from NASA’s STEREO spacecraft. Download here: https://svs.gsfc.nasa.gov/20278/ NASA/SwRI/Craig DeForest Most of the solar particles don’t reach the surface of Earth because our planet has a magnetic shield and an atmosphere to deflect them. But the Moon has no such protection. As computer models and lab experiments have shown, when protons smash into the Moon’s surface, which is made of a dusty and rocky material called regolith, they collide with electrons and recombine to form hydrogen atoms.
Then, the hydrogen atoms can migrate through the lunar surface and bond with the abundant oxygen atoms already present in minerals like silica to form hydroxyl (OH) molecules, a component of water, and water (H2O) molecules themselves.
Scientists have found evidence of both hydroxyl and water molecules in the Moon’s upper surface, just a few millimeters deep. These molecules leave behind a kind of chemical fingerprint — a noticeable dip in a wavy line on a graph that shows how light interacts with the regolith. With the current tools available, though, it is difficult to tell the difference between hydroxyl and water, so scientists use the term “water” to refer to either one or a mix of both molecules.
Many researchers think the solar wind is the main reason the molecules are there, though other sources like micrometeorite impacts could also help by creating heat and triggering chemical reactions.
In 2016, scientists discovered that water is released from the Moon during meteor showers. When a speck of comet debris strikes the moon, it vaporizes on impact, creating a shock wave in the lunar soil. With a sufficiently large impactor, this shock wave can breach the soil’s dry upper layer and release water molecules from a hydrated layer below. NASA’s LADEE spacecraft detected these water molecules as they entered the tenuous lunar atmosphere. NASA’s Goddard Space Flight Center Conceptual Image Lab Spacecraft measurements had already hinted that the solar wind is the primary driver of water, or its components, at the lunar surface. One key clue, confirmed by Yeo’s team’s experiment: the Moon’s water-related spectral signal changes over the course of the day.
In some regions, it’s stronger in the cooler morning and fades as the surface heats up, likely because water and hydrogen molecules move around or escape to space. As the surface cools again at night, the signal peaks again. This daily cycle points to an active source — most likely the solar wind—replenishing tiny amounts of water on the Moon each day.
To test whether this is true, Yeo and her colleague, Jason McLain, a research scientist at NASA Goddard, built a custom apparatus to examine Apollo lunar samples. In a first, the apparatus held all experiment components inside: a solar particle beam device, an airless chamber that simulated the Moon’s environment, and a molecule detector. Their invention allowed the researchers to avoid ever taking the sample out of the chamber — as other experiments did — and exposing it to contamination from the water in the air.
“It took a long time and many iterations to design the apparatus components and get them all to fit inside,” said McLain, “but it was worth it, because once we eliminated all possible sources of contamination, we learned that this decades-old idea about the solar wind turns out to be true.”
Using dust from two different samples picked up on the Moon by NASA’s Apollo 17 astronauts in 1972, Yeo and her colleagues first baked the samples to remove any possible water they could have picked up between air-tight storage in NASA’s space-sample curation facility at NASA’s Johnson Space Center in Houston and Goddard’s lab. Then, they used a tiny particle accelerator to bombard the dust with mock solar wind for several days — the equivalent of 80,000 years on the Moon, based on the high dose of the particles used.
They used a detector called a spectrometer to measure how much light the dust molecules reflected, which showed how the samples’ chemical makeup changed over time.
In the end, the team saw a drop in the light signal that bounced to their detector precisely at the point in the infrared region of the electromagnetic spectrum — near 3 microns — where water typically absorbs energy, leaving a telltale signature.
While they can’t conclusively say if their experiment made water molecules, the researchers reported in their study that the shape and width of the dip in the wavy line on their graph suggests that both hydroxyl and water were produced in the lunar samples.
By Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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By NASA
NASA’s Lucy spacecraft is 6 days and less than 50 million miles (80 million km) away from its second close encounter with an asteroid; this time, the small main belt asteroid Donaldjohanson.
Download high-resolution video and images from NASA’s Scientific Visualization Studio.
NASA/Dan Gallagher This upcoming event represents a comprehensive “dress rehearsal” for Lucy’s main mission over the next decade: the exploration of multiple Trojan asteroids that share Jupiter’s orbit around the Sun. Lucy’s first asteroid encounter – a flyby of the tiny main belt asteroid Dinkinesh and its satellite, Selam, on Nov. 1, 2023 – provided the team with an opportunity for a systems test that they will be building on during the upcoming flyby.
Lucy’s closest approach to Donaldjohanson will occur at 1:51pm EDT on April 20, at a distance of 596 miles (960 km). About 30 minutes before closest approach, Lucy will orient itself to track the asteroid, during which its high-gain antenna will turn away from Earth, suspending communication. Guided by its terminal tracking system, Lucy will autonomously rotate to keep Donaldjohanson in view. As it does this, Lucy will carry out a more complicated observing sequence than was used at Dinkinesh. All three science instruments – the high-resolution greyscale imager called L’LORRI, the color imager and infrared spectrometer called L’Ralph, and the far infrared spectrometer called L’TES – will carry out observation sequences very similar to the ones that will occur at the Trojan asteroids.
However, unlike with Dinkinesh, Lucy will stop tracking Donaldjohanson 40 seconds before the closest approach to protect its sensitive instruments from intense sunlight.
“If you were sitting on the asteroid watching the Lucy spacecraft approaching, you would have to shield your eyes staring at the Sun while waiting for Lucy to emerge from the glare. After Lucy passes the asteroid, the positions will be reversed, so we have to shield the instruments in the same way,” said encounter phase lead Michael Vincent of Southwest Research Institute (SwRI) in Boulder, Colorado. “These instruments are designed to photograph objects illuminated by sunlight 25 times dimmer than at Earth, so looking toward the Sun could damage our cameras.”
Fortunately, this is the only one of Lucy’s seven asteroid encounters with this challenging geometry. During the Trojan encounters, as with Dinkinesh, the spacecraft will be able to collect data throughout the entire encounter.
After closest approach, the spacecraft will “pitch back,” reorienting its solar arrays back toward the Sun. Approximately an hour later, the spacecraft will re-establish communication with Earth.
“One of the weird things to wrap your brain around with these deep space missions is how slow the speed of light is,” continued Vincent. “Lucy is 12.5 light minutes away from Earth, meaning it takes that long for any signal we send to reach the spacecraft. Then it takes another 12.5 minutes before we get Lucy’s response telling us we were heard. So, when we command the data playback after closest approach, it takes 25 minutes from when we ask to see the pictures before we get any of them to the ground.”
Once the spacecraft’s health is confirmed, engineers will command Lucy to transmit the science data from the encounter back to Earth, which is a process that will take several days.
Donaldjohanson is a fragment from a collision 150 million years ago, making it one of the youngest main belt asteroids ever visited by a spacecraft.
“Every asteroid has a different story to tell, and these stories weave together to paint the history of our solar system,” said Tom Statler, Lucy mission program scientist at NASA Headquarters in Washington. “The fact that each new asteroid we visit knocks our socks off means we’re only beginning to understand the depth and richness of that history. Telescopic observations are hinting that Donaldjohanson is going to have an interesting story, and I’m fully expecting to be surprised – again.”
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, designed and built the L’Ralph instrument and provides overall mission management, systems engineering and safety and mission assurance for Lucy. Hal Levison of SwRI’s office in Boulder, Colorado, is the principal investigator. SwRI, headquartered in San Antonio, also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft, designed the original orbital trajectory and provides flight operations. Goddard and KinetX Aerospace are responsible for navigating the Lucy spacecraft. The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, designed and built the L’LORRI (Lucy Long Range Reconnaissance Imager) instrument. Arizona State University in Tempe, Arizona, designed and build the L’TES (Lucy Thermal Emission Spectrometer) instrument. Lucy is the thirteenth mission in NASA’s Discovery Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.
By Katherine Kretke, Southwest Research Institute
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Karen Fox / Molly Wasser
Headquarters, Washington
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karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Nancy N. Jones
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Apr 14, 2025 EditorMadison OlsonContactNancy N. Jonesnancy.n.jones@nasa.govLocationGoddard Space Flight Center Related Terms
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
The Crew Module Test Article (CMTA), a full scale mockup of the Orion spacecraft, is seen in the Pacific Ocean as teams practice Artemis recovery operations during Underway Recovery Test-12 onboard USS Somerset off the coast of California, Saturday, March 29, 2025. NASA/Bill Ingalls Preparations for NASA’s next Artemis flight recently took to the seas as a joint NASA and Department of Defense team, led by NASA’s Exploration Ground Systems Program, spent a week aboard the USS Somerset off the coast of California practicing procedures for recovering the Artemis II spacecraft and crew.
Following successful completion of Underway Recovery Test-12 (URT-12) on Monday, NASA’s Landing and Recovery team and their Defense Department counterparts are certified to recover the Orion spacecraft as part of the upcoming Artemis II test flight that will send NASA astronauts Reid Wiseman, Victor Glover, and Christina Koch, as well as CSA (Canadian Space Agency) astronaut Jeremy Hansen, on a 10-day journey around the Moon.
“This will be NASA’s first crewed mission to the Moon under the Artemis program,” said Lili Villarreal, the landing and recovery director for Artemis II. “A lot of practice led up to this week’s event, and seeing everything come together at sea gives me great confidence that the air, water, ground, and medical support teams are ready to safely recover the spacecraft and the crew for this historic mission.”
A wave breaks inside the well deck of USS Somerset as teams work to recover the Crew Module Test Article (CMTA), a full scale replica of the Orion spacecraft, as they practice Artemis recovery operations during Underway Recovery Test-12 off the coast of California, Thursday, March 27, 2025.NASA/Joel Kowsky Once Orion reenters Earth’s atmosphere, the capsule will keep the crew safe as it slows from nearly 25,000 mph to about 325 mph. Then its system of 11 parachutes will deploy in a precise sequence to slow the capsule and crew to a relatively gentle 20 mph for splashdown off the coast of California. From the time it enters Earth’s atmosphere, the Artemis II spacecraft will fly 1,775 nautical miles to its landing spot in the Pacific Ocean. This direct approach allows NASA to control the amount of time the spacecraft will spend in extremely high temperature ranges.
The Artemis II astronauts trained during URT-11 in February 2024, when they donned Orion Crew Survival System suits and practiced a range of recovery operations at sea using the Crew Module Test Article, a stand -in for their spacecraft.
For the 12th training exercise, NASA astronauts Deniz Burnham and Andre Douglas, along with ESA (European Space Agency) astronaut Luca Parmitano, did the same, moving from the simulated crew module to USS Somerset, with helicopters, a team of Navy divers in small boats, NASA’s open water lead – a technical expert and lead design engineer for all open water operations – as well as Navy and NASA medical teams rehearsing different recovery scenarios.
Grant Bruner, left, and Gary Kirkendall, right, Orion suit technicians, are seen with ESA (European Space Agency) astronaut Luca Parmitano, second from left, and NASA astronauts Deniz Burnham, center, and Andre Douglas, as they prepare to take part in Artemis recovery operations as part of Underway Recovery Test-12 onboard USS Somerset off the coast of California, Thursday, March 27, 2025. NASA/Joel Kowsky “Allowing astronauts to participate when they are not directly involved in a mission gives them valuable experience by exposing them to a lot of different scenarios,” said Glover, who will pilot Artemis II. “Learning about different systems and working with ground control teams also broadens their skillsets and prepares them for future roles. It also allows astronauts like me who are assigned to the mission to experience other roles – in this case, I am serving in the role of Joe Acaba, Chief of the Astronaut Office.”
NASA astronaut and Artemis II pilot Victor Glover, right, speaks to NASA astronauts Andre Douglas and Deniz Burnham as they prepare to take part in practicing Artemis recovery procedures during Underway Recovery Test-12 onboard USS Somerset off the coast of California, Friday, March 28, 2025.NASA/Joel Kowsky NASA astronaut Deniz Burnham smiles after landing in a Navy helicopter onboard USS Somerset during Underway Recovery Test-12 off the coast of California, Thursday, March 27, 2025.NASA/Bill Ingalls As the astronauts arrive safely at the ship for medical checkouts, recovery teams focus on returning the spacecraft and its auxiliary ground support hardware to the amphibious transport dock.
Navy divers attach a connection collar to the spacecraft and an additional line to a pneumatic winch inside the USS Somerset’s well deck, allowing joint NASA and Navy teams to tow Orion toward the ship. A team of sailors and NASA recovery personnel inside the ship manually pull some of the lines to help align Orion with its stand, which will secure the spacecraft for its trip to the shore. Following a safe and precise recovery, sailors will drain the well deck of water, and the ship will make its way back to Naval Base San Diego.
The Artemis II test flight will confirm the foundational systems and hardware needed for human deep space exploration, taking another step toward missions on the lunar surface and helping the agency prepare for human missions to Mars.
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Allison Tankersley
Public Affairs Specialist
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Last Updated Mar 31, 2025 Related Terms
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By European Space Agency
The European Space Agency (ESA) has powered down its Gaia spacecraft after more than a decade spent gathering data that are now being used to unravel the secrets of our home galaxy.
On 27 March 2025, Gaia’s control team at ESA’s European Space Operations Centre carefully switched off the spacecraft’s subsystems and sent it into a ‘retirement orbit’ around the Sun.
Though the spacecraft’s operations are now over, the scientific exploitation of Gaia’s data has just begun.
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By NASA
Earth (ESD) Earth Explore Explore Earth Science Climate Change Air Quality Science in Action Multimedia Image Collections Videos Data For Researchers About Us 6 Min Read NASA Uses Advanced Radar to Track Groundwater in California
The Friant-Kern Canal supports water management in California’s San Joaquin Valley. A new airborne campaign is using NASA radar technology to understand how snowmelt replenishes groundwater in the area. Credits:
Bureau of Reclamation Where California’s towering Sierra Nevada surrender to the sprawling San Joaquin Valley, a high-stakes detective story is unfolding. The culprit isn’t a person but a process: the mysterious journey of snowmelt as it travels underground to replenish depleted groundwater reserves.
The investigator is a NASA jet equipped with radar technology so sensitive it can detect ground movements thinner than a nickel. The work could unlock solutions to one of the American West’s most pressing water challenges — preventing groundwater supplies from running dry.
“NASA’s technology has the potential to give us unprecedented precision in measuring where snowmelt is recharging groundwater,” said Erin Urquhart, program manager for NASA’s Earth Action Water Resources program at NASA Headquarters in Washington. “This information is vital for farmers, water managers, and policymakers trying to make the best possible decisions to protect water supplies for agriculture and communities.”
Tracking Water Beneath the Surface
In late February, a NASA aircraft equipped with Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) conducted the first of six flights planned for this year, passing over a roughly 25-mile stretch of the Tulare Basin in the San Joaquin Valley, where foothills meet farmland. It’s a zone experts think holds a key to maintaining water supplies for one of America’s most productive agricultural regions.
Much of the San Joaquin Valley’s groundwater comes from the melting of Sierra Nevada snow. “For generations, we’ve been managing water in California without truly knowing where that meltwater seeps underground and replenishes groundwater,” said Stanford University geophysicist and professor Rosemary Knight, who is leading the research.
This image from the MODIS instrument on NASA’s Terra satellite, captured on March 8, 2025, shows the Tulare Basin area in Southern California, where foothills meet farmlands. The region is a crucial area for groundwater recharge efforts aimed at making the most of the state’s water resources. Credits: NASA Earth Observatory image by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. The process is largely invisible — moisture filtering through rock and sediment, and vanishing beneath orchards and fields. But as the liquid moves downhill, it follows a pattern. Water flows into rivers and streams, some of it eventually seeping underground at the valley’s edge or as the waterways spread into the valley. As the water moves through the ground, it can create slight pressure that in turn pushes the surface upward. The movement is imperceptible to the human eye, but NASA’s advanced radar technology can detect it.
“Synthetic aperture radar doesn’t directly see water,” explained Yunling Lou, who leads the UAVSAR program at NASA’s Jet Propulsion Laboratory in Southern California. “We’re measuring changes in surface elevation — smaller than a centimeter — that tell us where the water is.”
These surface bulges create what Knight calls an “InSAR recharge signature.” By tracking how these surface bulges migrate from the mountains into the valley, the team hopes to pinpoint where groundwater replenishment occurs and, ultimately, quantify the amount of water naturally recharging the system.
Previous research using satellite-based InSAR (Interferometric Synthetic Aperture Radar) has shown that land in the San Joaquin Valley uplifts and subsides with the seasons, as the groundwater is replenished by Sierra snowmelt. But the satellite radar couldn’t uniquely identify the recharge paths. Knight’s team combined the satellite data with images of underground sediments, acquired using an airborne electromagnetic system, and was able to map the major hidden subsurface water pathways responsible for aquifer recharge.
NASA’s airborne UAVSAR system will provide even more detailed data, potentially allowing researchers to have a clearer view of where and how fast water is soaking back into the ground and recharging the depleted aquifers.
In 2025, NASA’s UAVSAR system on a Gulfstream-III jet (shown over a desert landscape) is conducting six planned advanced radar surveys to map how and where groundwater is recharging parts of California’s southern San Joaquin Valley. Credits: NASA Supporting Farmers and Communities
California’s Central Valley produces over a third of America’s vegetables and two-thirds of its fruits and nuts. The southern portion of this agricultural powerhouse is the San Joaquin Valley, where most farming operations rely heavily on groundwater, especially during drought years.
Water managers have occasionally been forced to impose restrictions on groundwater pumping as aquifer levels drop. Some farmers now drill increasingly deeper wells, driving up costs and depleting reserves.
“Knowing where recharge is happening is vital for smart water management,” said Aaron Fukuda, general manager of the Tulare Irrigation District, a water management agency in Tulare County that oversees irrigation and groundwater recharge projects.
“In dry years, when we get limited opportunities, we can direct flood releases to areas that recharge efficiently, avoiding places where water would just evaporate or take too long to soak in,” Fukuda said. “In wetter years, like 2023, it’s even more crucial — we need to move water into the ground as quickly as possible to prevent flooding and maximize the amount absorbed.”
NASA’s Expanding Role in Water Monitoring
NASA’s ongoing work to monitor and manage Earth’s water combines a range of cutting-edge technologies that complement one another, each contributing unique insights into the challenges of groundwater management.
The upcoming NISAR (NASA-ISRO Synthetic Aperture Radar) mission, a joint project between NASA and the Indian Space Research Organisation (ISRO) set to launch in coming months, will provide global-scale radar data to track land and ice surface changes — including signatures of groundwater movement — every 12 days.
The NISAR satellite (shown in this artist’s concept) has a large radar antenna designed to monitor Earth’s land and ice changes with unprecedented detail. Credits: NASA/JPL-Caltech In parallel, the GRACE satellites — operated by the German Aerospace Center, German Research Centre for Geosciences, and NASA — have transformed global groundwater monitoring by detecting tiny variations in Earth’s gravity, offering a broad view of monthly water storage changes across large regions.
The Gravity Recovery and Climate Experiment and Follow-On (GRACE and GRACE-FO) missions have helped expose major declines in aquifers, including in California’s Central Valley. But their coarser resolution calls for complementary tools that can, for example, pinpoint recharge hotspots with greater precision.
Together, these technologies form a powerful suite of tools that bridge the gap between regional-scale monitoring and localized water management. NASA’s Western Water Applications Office (WWAO) also plays a key role in ensuring that this wealth of data is accessible to water managers and others, offering platforms like the Visualization of In-situ and Remotely-Sensed Groundwater Observation (VIRGO) dashboard to facilitate informed decision-making.
“Airborne campaigns like this one in the San Joaquin test how our technology can deliver tangible benefits to American communities,” said Stephanie Granger, WWAO’s director at NASA’s Jet Propulsion Laboratory. “We partner with local water managers to evaluate tools that have the potential to strengthen water supplies across the Western United States.”
By Emily DeMarco
NASA Headquarters
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Emily DeMarco
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Last Updated Mar 20, 2025 Related Terms
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