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By NASA
4 min read
NASA Satellites Reveal Abrupt Drop in Global Freshwater Levels
Earth (ESD) Earth Home Explore Climate Change Science in Action Multimedia Data For Researchers GRACE satellites measure gravity as they orbit the planet to reveal shifting levels of water on the Earth (artist’s concept). NASA/JPL-Caltech An international team of scientists using observations from NASA-German satellites found evidence that Earth’s total amount of freshwater dropped abruptly starting in May 2014 and has remained low ever since. Reporting in Surveys in Geophysics, the researchers suggested the shift could indicate Earth’s continents have entered a persistently drier phase.
From 2015 through 2023, satellite measurements showed that the average amount of freshwater stored on land — that includes liquid surface water like lakes and rivers, plus water in aquifers underground — was 290 cubic miles (1,200 cubic km) lower than the average levels from 2002 through 2014, said Matthew Rodell, one of the study authors and a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s two and a half times the volume of Lake Erie lost.”
During times of drought, along with the modern expansion of irrigated agriculture, farms and cities must rely more heavily on groundwater, which can lead to a cycle of declining underground water supplies: freshwater supplies become depleted, rain and snow fail to replenish them, and more groundwater is pumped. The reduction in available water puts a strain on farmers and communities, potentially leading to famine, conflicts, poverty, and an increased risk of disease when people turn to contaminated water sources, according to a UN report on water stress published in 2024.
The team of researchers identified this abrupt, global decrease in freshwater using observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, operated by the German Aerospace Center, German Research Centre for Geosciences, and NASA. GRACE satellites measure fluctuations in Earth’s gravity on monthly scales that reveal changes in the mass of water on and under the ground. The original GRACE satellites flew from March 2002 to October 2017. The successor GRACE–Follow On (GRACE–FO) satellites launched in May 2018.
This map shows the years that terrestrial water storage hit a 22-year minimum (i.e., the land was driest) at each location, based on data from the GRACE and GRACE/FO satellites. A significantly large portion of the global land surface reached this minimum in the nine years since 2015, which happen to be the nine warmest years in the modern temperature record. Image by NASA Earth Observatory/Wanmei Liang with data courtesy of Mary Michael O’Neill The decline in global freshwater reported in the study began with a massive drought in northern and central Brazil, and was followed shortly by a series of major droughts in Australasia, South America, North America, Europe, and Africa. Warmer ocean temperatures in the tropical Pacific from late 2014 into 2016, culminating in one of the most significant El Niño events since 1950, led to shifts in atmospheric jet streams that altered weather and rainfall patterns around the world. However, even after El Niño subsided, global freshwater failed to rebound. In fact, Rodell and team report that 13 of the world’s 30 most intense droughts observed by GRACE occurred since January 2015. Rodell and colleagues suspect that global warming might be contributing to the enduring freshwater depletion.
Global warming leads the atmosphere to hold more water vapor, which results in more extreme precipitation, said NASA Goddard meteorologist Michael Bosilovich. While total annual rain and snowfall levels may not change dramatically, long periods between intense precipitation events allow the soil to dry and become more compact. That decreases the amount of water the ground can absorb when it does rain.
“The problem when you have extreme precipitation,” Bosilovich said, “is the water ends up running off,” instead of soaking in and replenishing groundwater stores. Globally, freshwater levels have stayed consistently low since the 2014-2016 El Niño, while more water remains trapped in the atmosphere as water vapor. “Warming temperatures increase both the evaporation of water from the surface to the atmosphere, and the water-holding capacity of the atmosphere, increasing the frequency and intensity of drought conditions,” he noted.
While there are reasons to suspect that the abrupt drop in freshwater is largely due to global warming, it can be difficult to definitively link the two, said Susanna Werth, a hydrologist and remote sensing scientist at Virginia Tech, who was not affiliated with the study. “There are uncertainties in climate predictions,” Werth said. “Measurements and models always come with errors.”
It remains to be seen whether global freshwater will rebound to pre-2015 values, hold steady, or resume its decline. Considering that the nine warmest years in the modern temperature record coincided with the abrupt freshwater decline, Rodell said, “We don’t think this is a coincidence, and it could be a harbinger of what’s to come.”
By James R. Riordon
NASA’s Earth Science News Team
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Last Updated Nov 15, 2024 Editor James Riordon Contact James Riordon james.r.riordon@nasa.gov Location NASA Goddard Space Flight Center Related Terms
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4 min read NASA Satellites Find Snow Didn’t Offset Southwest US Groundwater Loss
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This artist’s concept depicts a potential volcanic moon between the exoplanet WASP-49 b, left, and its parent star. New evidence indicating that a massive sodium cloud observed near WASP-49 b is produced by neither the planet nor the star has prompted researchers to ask if its origin could be an exomoon.NASA/JPL-Caltech The existence of a moon located outside our solar system has never been confirmed but a new NASA-led study may provide indirect evidence for one.
New research done at NASA’s Jet Propulsion Laboratory reveals potential signs of a rocky, volcanic moon orbiting an exoplanet 635 light-years from Earth. The biggest clue is a sodium cloud that the findings suggest is close to but slightly out of sync with the exoplanet, a Saturn-size gas giant named WASP-49 b, although additional research is needed to confirm the cloud’s behavior. Within our solar system, gas emissions from Jupiter’s volcanic moon Io create a similar phenomenon.
Although no exomoons (moons of planets outside our solar system) have been confirmed, multiple candidates have been identified. It’s likely these planetary companions have gone undetected because they are too small and dim for current telescopes to detect.
The sodium cloud around WASP-49 b was first detected in 2017, catching the attention of Apurva Oza, formerly a postdoctoral researcher at NASA’s Jet Propulsion Laboratory and now a staff scientist at Caltech, which manages JPL. Oza has spent years investigating how exomoons might be detected via their volcanic activity. For example, Io, the most volcanic body in our solar system, constantly spews sulfur dioxide, sodium, potassium, and other gases that can form vast clouds around Jupiter up to 1,000 times the giant planet’s radius. It’s possible that astronomers looking at another star system could detect a gas cloud like Io’s even if the moon itself were too small to see.
Exomoons — moons around planets outside our solar system — are most likely too small to observe directly with current technology. In this video, learn how scientists tracked the motion of a sodium cloud 635 light-years away and found that it could be created by volcanos on a potential exomoon. NASA/JPL-Caltech Both WASP-49 b and its star are composed mostly of hydrogen and helium, with trace amounts of sodium. Neither contains enough sodium to account for the cloud, which appears to be coming from a source that is producing roughly 220,000 pounds (100,000 kilograms) of sodium per second. Even if the star or planet could produce that much sodium, it’s unclear what mechanism could eject it into space.
Could the source be a volcanic exomoon? Oza and his colleagues set out to try to answer that question. The work immediately proved challenging because from such a great distance, the star, planet, and cloud often overlap and occupy the same tiny, faraway point in space. So the team had to watch the system over time.
A Cloud on the Move
As detailed in a new study published in the Astrophysical Journal Letters, they found several pieces of evidence that suggest the cloud is created by a separate body orbiting the planet, though additional research is needed to confirm the cloud’s behavior. For example, twice their observations indicated the cloud suddenly increased in size, as if being refueled, when it was not next to the planet.
New NASA-led research suggests a sodium cloud seen around the exoplanet WASP-49 b might be created by a volcanic moon, which is depicted in this artist’s concept. Jupiter’s fiery moon Io produces a similar cloud. NASA/JPL-Caltech They also observed the cloud moving faster than the planet in a way that would seem impossible unless it was being generated by another body moving independent of, and faster, than the planet.
“We think this is a really critical piece of evidence,” said Oza. “The cloud is moving in the opposite direction that physics tells us it should be going if it were part of the planet’s atmosphere.”
While these observations have intrigued the research team, they say they would need to observe the system for longer to be sure of the cloud’s orbit and structure.
A Chance of Volcanic Clouds
For part of their sleuthing, the researchers used the European Southern Observatory’s Very Large Telescope in Chile. Oza’s co-author Julia Seidel, a research fellow at the observatory, established that the cloud is located high above the planet’s atmosphere, much like the cloud of gas Io produces around Jupiter.
They also used a computer model to illustrate the exomoon scenario and compare it to the data. The exoplanet WASP-49 b orbits the star every 2.8 days with clocklike regularity, but the cloud appeared and disappeared behind the star or behind the planet at seemingly irregular intervals. Using their model, Oza and team showed that a moon with an eight-hour orbit around the planet could explain the cloud’s motion and activity, including the way it sometimes seemed to move in front of the planet and did not seem to be associated with a particular region of the planet.
“The evidence is very compelling that something other than the planet and star are producing this cloud,” said Rosaly Lopes, a planetary geologist at JPL who co-authored the study with Oza. “Detecting an exomoon would be quite extraordinary, and because of Io, we know that a volcanic exomoon is possible.”
A Violent End
On Earth, volcanoes are driven by heat in its core left over from the planet’s formation. Io’s volcanoes, on the other hand, are driven by Jupiter’s gravity, which squeezes the moon as it gets closer to the planet then reduces its “grip” as the moon moves away. This flexing heats the small moon’s interior, leading to a process called tidal volcanism.
If WASP-49 b has a moon similar in size to Earth’s, Oza and team estimate that the rapid loss of mass combined with the squeezing from the planet’s gravity will eventually cause it to disintegrate.
“If there really is a moon there, it will have a very destructive ending,” said Oza.
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Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
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Last Updated Oct 10, 2024 Related Terms
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This low-angle self-portrait of NASA’s Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called “Buckskin” on lower Mount Sharp. When NASA conducts research beyond our world, scientists on Earth prepare as much as possible before sending instruments on extraterrestrial journeys. One way to prepare for these exploration missions is by using machine learning techniques to develop algorithms with data from commercial instruments or from flight instruments on planetary missions.
For example, NASA uses mass spectrometer instruments on Mars missions to analyze surface samples and identify organic molecules. Developing machine learning algorithms before missions can help make the process of analyzing planetary data faster and more efficient during time-limited space operations.
In 2022, Victoria Da Poian, a data scientist supporting machine learning research at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, collaborated with NASA’s Center of Excellence for Collaborative Innovation to run two machine learning-based open science challenges, which sought ideas and solutions from the public. Solvers worldwide were invited to analyze chemical data sampled from commercial instruments located at NASA centers and data from the Sample Analysis at Mars (SAM) testbed, which is a replica of the instrument suite onboard the Curiosity rover. The challenges encouraged participants to be creative in their approaches and to provide detailed descriptions of their method and code.
Da Poian said her team decided to use public competitions for this project to gain new perspectives: “We were really interested in hearing from people who aren’t in our field and weren’t biased by the data’s meaning or our scientific rules.”
As a result, more than 1150 unique participants from all over the world participated in the competitions, and more than 600 solutions contributing models to analyze rock and soil samples relevant to planetary science were submitted. The challenges served as proof-of-concept projects to analyze the feasibility of combining data from multiple sources in a single machine learning application.
In addition to benefitting from the variety of perspectives offered by challenge participants, Da Poian says the challenges were both time- and cost-efficient methods for discovering solutions. At the same time, the challenges invited the global community to participate in NASA research in support of future space exploration missions, and winners received $60,000 in total prizes across the two opportunities.
Da Poian used lessons learned to develop a new challenge with Frontier Development Lab , an international research collaboration that brings together researchers and domain experts to tackle complex problems using machine learning technologies.
The competition, titled “Stay Curious: Leveraging Machine Learning to Analyze & Interpret the Measurements of Mars Planetary Instruments,” ran from June to August 2024. Results included cleaning SAM data collected on Mars, processing data for a consistent, machine learning-ready dataset combining commercial and flight instrument data, investigating data augmentation techniques to increase the limited data volume available for the challenge, and exploring machine learning techniques to help predict the chemical composition of Martian terrain.
“The machine learning challenges opened the door to how we can use laboratory data to train algorithms and then use that to train flight data,” said Da Poian. “Being able to use laboratory data that we’ve collected for many years is a huge opportunity for us, and the results so far are extremely encouraging.”
Find more opportunities: https://www.nasa.gov/get-involved/
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By NASA
Oct. 1, 2024
NASA astronaut Josh Cassada holds a roll-out solar array as he rides the Canadarm2 robotic arm during a spacewalk in support of the Expedition 68 mission aboard the International Space Station on Dec. 3, 2022. Credit: NASA Three-time Spacewalker Josh Cassada to Retire from NASA
NASA astronaut Josh Cassada retired Oct. 1, after 11 years of service to the agency across multiple programs, including 157 days in space and three spacewalks. Cassada also is a retired United States Navy captain and naval aviator with more than two decades of service.
Cassada served as pilot of NASA’s SpaceX Crew-5 mission and Expedition 68 flight engineer aboard the International Space Station, executing myriad maintenance, contingency, and upgrade activities inside the station while also contributing to hundreds of experiments and technology demonstrations. His three spacewalks outside of the orbiting laboratory totaled more than 21 hours, successfully installing a pair of International Space Station Roll-Out Solar Arrays (IROSAs) to boost the station’s electrical capacity. Cassada, alongside crewmate NASA astronaut Frank Rubio, also assembled the infrastructure for a future IROSA installation and fully restored a malfunctioning legacy solar array.
“I want to extend my sincere gratitude to Josh for his dedication and service to human space exploration,” said NASA Johnson Space Center Director Vanessa Wyche. “Josh’s contributions and achievements to the advancement of science and exploration will inspire the next generation of explorers, the Artemis generation, and benefit humanity for decades to come.”
NASA astronaut Josh Cassada poses for a portrait in his extravehicular mobility unit spacesuit on August 8, 2022. Credit: NASA/Robert Markowitz Throughout Expedition 68, Cassada and his crewmates completed extensive problem-solving with ground teams, including the modification of the SpaceX Dragon spacecraft to accommodate an additional crew member in the event of an emergency return, and leveraged the crew’s various skill sets and training to ensure continued safe and effective operations for current and future crews.
In Houston, Cassada served as a capsule communicator in NASA’s Mission Control Center and assistant to the chief of the Astronaut Office for space station operations. As a physicist and test pilot, Cassada also contributed to the development of NASA’s Commercial Crew Program and Orion spacecraft and represented the Astronaut Office in technical and operational reviews of scientific experiments such as the Alpha Magnetic Spectrometer and Cold Atom Lab.
“Josh has played a significant role in NASA’s deliverance of reliable and cost-effective human transportation to and from the space station,” said Norm Knight, director of flight operations at NASA Johnson. “Through his dedication and commitment to human spaceflight exploration, Josh’s work will continue to push us forward on our journey back to the Moon, and beyond. We will miss him and are excited to see what his next journey entails.”
As he transitions from government service, Cassada will return to the private sector, working on extremely low light detection technologies with broad and emerging applications in various areas, including quantum networks and computing, remote sensing, long-range communication, semiconductor manufacturing, and medical imaging.
“I am incredibly grateful for my many opportunities here at NASA,” Cassada said, “and especially to have served alongside some of the most amazing people both on and off our planet, accomplishing things that are only possible when we work and innovate together as a team. As humans, we explore . And each scientific adventure, whether in a lab on Earth or in space, requires courage to explore and advance society. I am incredibly fortunate to have been surrounded by explorers during my entire career so far and going forward. An expedition may seem daunting, but it’s a lot less so when you’re prepared and with the right crewmates.”
Before his selection by NASA in 2013 as a member of NASA’s 21st Class, Cassada earned his doctorate in High Energy Particle Physics from the University of Rochester, New York and was a U.S. Navy pilot, instructor pilot, test pilot, and instructor test pilot. Throughout his career, Cassada has accumulated more than 4,000 flight hours in over 50 different aircraft and has been awarded various military and civilian awards.
Cassada graduated from White Bear Lake Area High School in Minnesota in 1991 and received his bachelor’s in Physics in 1995 from Albion College in Michigan.
Learn more about International Space Station research and operations at:
https://www.nasa.gov/station
-end-
Courtney Beasley
Johnson Space Center, Houston
281-483-5111
courtney.m.beasley@nasa.gov
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