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By NASA
3 Min Read NASA Scientists Find New Human-Caused Shifts in Global Water Cycle
Cracked mud and salt on the valley floor in Death Valley National Park in California can become a reflective pool after rains. (File photo) Credits: NPS/Kurt Moses In a recently published paper, NASA scientists use nearly 20 years of observations to show that the global water cycle is shifting in unprecedented ways. The majority of those shifts are driven by activities such as agriculture and could have impacts on ecosystems and water management, especially in certain regions.
“We established with data assimilation that human intervention in the global water cycle is more significant than we thought,” said Sujay Kumar, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-author of the paper published in the Proceedings of the National Academy of Sciences.
The shifts have implications for people all over the world. Water management practices, such as designing infrastructure for floods or developing drought indicators for early warning systems, are often based on assumptions that the water cycle fluctuates only within a certain range, said Wanshu Nie, a research scientist at NASA Goddard and lead author of the paper.
“This may no longer hold true for some regions,” Nie said. “We hope that this research will serve as a guide map for improving how we assess water resources variability and plan for sustainable resource management, especially in areas where these changes are most significant.”
One example of the human impacts on the water cycle is in North China, which is experiencing an ongoing drought. But vegetation in many areas continues to thrive, partially because producers continue to irrigate their land by pumping more water from groundwater storage, Kumar said. Such interrelated human interventions often lead to complex effects on other water cycle variables, such as evapotranspiration and runoff.
Nie and her colleagues focused on three different kinds of shifts or changes in the cycle: first, a trend, such as a decrease in water in a groundwater reservoir; second, a shift in seasonality, like the typical growing season starting earlier in the year, or an earlier snowmelt; and third a change in extreme events, like “100-year floods” happening more frequently.
The scientists gathered remote sensing data from 2003 to 2020 from several different NASA satellite sources: the Global Precipitation Measurement mission satellite for precipitation data, a soil moisture dataset from the European Space Agency’s Climate Change Initiative, and the Gravity Recovery and Climate Experiment satellites for terrestrial water storage data. They also used products from the Moderate Resolution Imaging Spectroradiometer satellite instrument to provide information on vegetation health.
“This paper combines several years of our team’s effort in developing capabilities on satellite data analysis, allowing us to precisely simulate continental water fluxes and storages across the planet,” said Augusto Getirana, a research scientist at NASA Goddard and a co-author of the paper.
The study results suggest that Earth system models used to simulate the future global water cycle should evolve to integrate the ongoing effects of human activities. With more data and improved models, producers and water resource managers could understand and effectively plan for what the “new normal” of their local water situation looks like, Nie said.
By Erica McNamee
NASA’s Goddard Space Flight Center, Greenbelt, Maryland
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Last Updated Jan 16, 2025 EditorKate D. RamsayerContactKate D. Ramsayerkate.d.ramsayer@nasa.gov Related Terms
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By NASA
This artist’s illustration represents the results from a new study that examines the effects of X-ray and other high-energy radiation unleashed on potential exoplanets from Wolf 359, a nearby red dwarf star. Researchers used Chandra and XMM-Newton to study the impact of steady X-ray and energetic ultraviolet radiation from Wolf 359 on the atmospheres of planets that might be orbiting the star. They found that only a planet with greenhouse gases like carbon dioxide in its atmosphere and at a relatively large distance away from Wolf 359 would have a chance to support life as we know it.X-ray: NASA/CXC/SAO/S.Wolk, et al.; Illustration: NASA/CXC/SAO/M.Weiss; Image processing: NASA/CXC/SAO/N. Wolk Planets around other stars need to be prepared for extreme weather conditions, according to a new study from NASA’s Chandra X-ray Observatory and ESA’s (European Space Agency’s) XMM-Newton that examined the effects of X-rays on potential planets around the most common type of stars.
Astronomers found that only a planet with greenhouse gases in its atmosphere like Earth and at a relatively large distance away from the star they studied would have a chance to support life as we know it around a nearby star.
Wolf 359 is a red dwarf with a mass about a tenth that of the Sun. Red dwarf stars are the most common stars in the universe and live for billions of years, providing ample time for life to develop. At a distance of only 7.8 light-years away, Wolf 359 is also one of the closest stars to the solar system.
“Wolf 359 can help us unlock the secrets around stars and habitability,” said Scott Wolk of the Center for Astrophysics | Harvard & Smithsonian (CfA), who led the study. “It’s so close and it belongs to such an important class of stars – it’s a great combination.”
Because red dwarfs are the most prevalent types of stars, astronomers have looked hard to find exoplanets around them. Astronomers have found some evidence for two planets in orbit around Wolf 359 using optical telescopes, but those conclusions have been challenged by other scientists.
“While we don’t have proof of planets around Wolf 359 yet, it seems very possible that it hosts multiple planets,” Wolk added. “This makes it an excellent test bed to look at what planets would experience around this kind of star.”
Wolk and his colleagues used Chandra and XMM to study the amounts of steady X-rays and extreme ultraviolet (UV) radiation – the most energetic type of UV radiation – that Wolf 359 would unleash on the possible planets around it.
They found that Wolf 359 is producing enough damaging radiation that only a planet with greenhouse gases like carbon dioxide in its atmosphere – and located at a relatively large distance from the star – would likely be able to sustain life.
“Just being far enough away from the star’s harmful radiation wouldn’t be enough to make it habitable,” said co-author Vinay Kashyap, also of CfA. “A planet around Wolf 359 would also need to be blanketed in greenhouse gases like Earth is.”
To study the effects of energetic radiation on the habitability of the planet candidates, the team considered the star’s habitable zone – the region around a star where liquid water could exist on a planet’s surface.
The outer limit of the habitable zone for Wolf 359 is about 15% of the distance between Earth and the Sun, because the red dwarf is much less bright than the Sun. Neither of the planet candidates for this system is located in Wolf 359’s habitable zone, with one too close to the star and the other too far out.
“If the inner planet is there, the X-ray and extreme UV radiation it is subjected to would destroy the atmosphere of this planet in only about a million years,” said co-author Ignazio Pillitteri of CfA and the National Institute for Astrophysics in Palermo, Italy.
The team also considered the effects of radiation on as-yet undetected planets within the habitable zone. They concluded that a planet like the Earth in the middle of the habitable zone should be able to sustain an atmosphere for almost two billion years, while one near the outer edge could last indefinitely, helped by the warming effects of greenhouse gases.
Another big danger for planets orbiting stars like Wolf 359 is from X-ray flares, or occasional bright bursts of X-rays, on top of the steady, everyday output from the star. Combining observations made with Chandra and XMM-Newton resulted in the discovery of 18 X-ray flares from Wolf 359 over 3.5 days.
Extrapolating from these observed flares, the team expects that much more powerful and damaging flares would occur over longer periods of time. The combined effects of the steady X-ray and UV radiation and the flares mean that any planet located in the habitable zone is unlikely to have a significant atmosphere long enough for multicellular life, as we know it on Earth, to form and survive. The exception is the habitable zone’s outer edge if the planet has a significant greenhouse effect.
These results were presented at the 245th meeting of the American Astronomical Society in National Harbor, Maryland, and are being prepared for publication in a journal. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
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By NASA
Webb Webb News Latest News Latest Images Blog (offsite) Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read Newfound Galaxy Class May Indicate Early Black Hole Growth, Webb Finds
A team of astronomers sifted through James Webb Space Telescope data from multiple surveys to compile one of the largest samples of “little red dots” to date. Credits:
NASA, ESA, CSA, STScI, Dale Kocevski (Colby College). In December 2022, less than six months after commencing science operations, NASA’s James Webb Space Telescope revealed something never seen before: numerous red objects that appear small on the sky, which scientists soon called “little red dots” (LRDs). Though these dots are quite abundant, researchers are perplexed by their nature, the reason for their unique colors, and what they convey about the early universe.
A team of astronomers recently compiled one of the largest samples of LRDs to date, nearly all of which existed during the first 1.5 billion years after the big bang. They found that a large fraction of the LRDs in their sample showed signs of containing growing supermassive black holes.
“We’re confounded by this new population of objects that Webb has found. We don’t see analogs of them at lower redshifts, which is why we haven’t seen them prior to Webb,” said Dale Kocevski of Colby College in Waterville, Maine, and lead author of the study. “There’s a substantial amount of work being done to try to determine the nature of these little red dots and whether their light is dominated by accreting black holes.”
Image A: Little Red Dots (NIRCam Image)
A team of astronomers sifted through James Webb Space Telescope data from multiple surveys to compile one of the largest samples of “little red dots” to date. From their sample, they found that these mysterious red objects that appear small on the sky emerge in large numbers around 600 million years after the big bang and undergo a rapid decline in quantity around 1.5 billion years after the big bang. NASA, ESA, CSA, STScI, Dale Kocevski (Colby College). A Potential Peek Into Early Black Hole Growth
A significant contributing factor to the team’s large sample size of LRDs was their use of publicly available Webb data. To start, the team searched for these red sources in the Cosmic Evolution Early Release Science (CEERS) survey before widening their scope to other extragalactic legacy fields, including the JWST Advanced Deep Extragalactic Survey (JADES) and the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) survey.
The methodology used to identify these objects also differed from previous studies, resulting in the census spanning a wide redshift range. The distribution they discovered is intriguing: LRDs emerge in large numbers around 600 million years after the big bang and undergo a rapid decline in quantity around 1.5 billion years after the big bang.
The team looked toward the Red Unknowns: Bright Infrared Extragalactic Survey (RUBIES) for spectroscopic data on some of the LRDs in their sample. They found that about 70 percent of the targets showed evidence for gas rapidly orbiting 2 million miles per hour (1,000 kilometers per second) – a sign of an accretion disk around a supermassive black hole. This suggests that many LRDs are accreting black holes, also known as active galactic nuclei (AGN).
“The most exciting thing for me is the redshift distributions. These really red, high-redshift sources basically stop existing at a certain point after the big bang,” said Steven Finkelstein, a co-author of the study at the University of Texas at Austin. “If they are growing black holes, and we think at least 70 percent of them are, this hints at an era of obscured black hole growth in the early universe.”
Contrary to Headlines, Cosmology Isn’t Broken
When LRDs were first discovered, some suggested that cosmology was “broken.” If all of the light coming from these objects was from stars, it implied that some galaxies had grown so big, so fast, that theories could not account for them.
The team’s research supports the argument that much of the light coming from these objects is from accreting black holes and not from stars. Fewer stars means smaller, more lightweight galaxies that can be understood by existing theories.
“This is how you solve the universe-breaking problem,” said Anthony Taylor, a co-author of the study at the University of Texas at Austin.
Curiouser and Curiouser
There is still a lot up for debate as LRDs seem to evoke even more questions. For example, it is still an open question as to why LRDs do not appear at lower redshifts. One possible answer is inside-out growth: As star formation within a galaxy expands outward from the nucleus, less gas is being deposited by supernovas near the accreting black hole, and it becomes less obscured. In this case, the black hole sheds its gas cocoon, becomes bluer and less red, and loses its LRD status.
Additionally, LRDs are not bright in X-ray light, which contrasts with most black holes at lower redshifts. However, astronomers know that at certain gas densities, X-ray photons can become trapped, reducing the amount of X-ray emission. Therefore, this quality of LRDs could support the theory that these are heavily obscured black holes.
The team is taking multiple approaches to understand the nature of LRDs, including examining the mid-infrared properties of their sample, and looking broadly for accreting black holes to see how many fit LRD criteria. Obtaining deeper spectroscopy and select follow-up observations will also be beneficial for solving this currently “open case” about LRDs.
“There’s always two or more potential ways to explain the confounding properties of little red dots,” said Kocevski. “It’s a continuous exchange between models and observations, finding a balance between what aligns well between the two and what conflicts.”
These results were presented in a press conference at the 245th meeting of the American Astronomical Society in National Harbor, Maryland, and have been submitted for publication in The Astrophysical Journal.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
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Science – Dale Kocevski (Colby College)
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Article: Webb Science: Galaxies Through Time
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Last Updated Jan 14, 2025 Editor Stephen Sabia Contact Laura Betz laura.e.betz@nasa.gov Related Terms
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
Artist concept highlighting the novel approach proposed by the 2025 NIAC awarded selection of the Thermo-Photo-Catalysis of Water for Crewed Mars Transit Spacecraft Oxygen Supply concept.NASA/Saurabh Vilekar Saurabh Vilekar
Precision Combustion
Precision Combustion, Inc. (PCI) proposes to develop a uniquely compact, lightweight, low-power, and durable Microlith® Thermo-Photo-Catalytic (TPC) Reactor for crewed Mars transit spacecraft O2 supply. As crewed space exploration mission destinations move from low Earth orbit to sustained lunar surface habitation toward Mars exploration, the need becomes more intense to supplant heritage physico-chemical unit operations employed for crewed spacecraft cabin CO2 removal, CO2 reduction, and O2 supply. The primary approach to date has been toward incremental improvement of the heritage, energy intensive process technologies used aboard the International Space Station (ISS), particularly for water electrolysis-based O2 generation. A major breakthrough is necessary to depose these energy intensive process technologies either partly or completely. This is achievable by considering the recent advances in photocatalysis. Applications are emerging for converting CO2 to useful commodity products and generating H2 from atmospheric water vapor. Considering these developments, a low power thermo-photo-catalytic process to replace the heritage high-power water electrolysis process is proposed for application to a Mars transit vehicle life support system (LSS) functional architecture. A key component in realizing this breakthrough is utilizing a catalyst substrate such as Microlith that affords high surface area and promotes mass transport to the catalyst surface. The proposed TPC oxygenator is expected to operate passively to continually renew the O2 content of the cabin atmosphere. The targeted mission for the proposed TPC oxygenator technology deployment is a 2039 Long Stay, Earth-Mars-Earth mission opportunity. This mission as defined by the Moon to Mars (M2M) 2024 review consists of 337.9 days outbound, 348.5 days in Mars vicinity, and 295.8 days return for a total 982.2-day mission. The proposed Microlith oxygenator technology, if successful, is envisioned to replace the OGA technology in the LSS process architecture with significant weight and power savings. In Phase I, we will demonstrate technical feasibility of Microlith TPC for O2 generation, interface requirements, and integration trade space and a clear path towards a prototype demonstration in Phase II will also be described in the final report.
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Artist concept highlighting the novel approach proposed by the 2025 NIAC awarded selection of Inflatable Starshade for Earthlike Exoplanets concept.NASA/John Mather John Mather
NASA Goddard Space Flight Center
We will design the first family of ISEE’s (Inflatable Starshade for Earthlike Exoplanets) with sizes from 35 to 100 m diameter. A starshade would enable any telescope to observe exoplanets, a top priority for astronomy worldwide. Compared with other starshade concepts, we aim for a lower mass, cost and complexity, while still providing high performance and science yield (>100 targets). Our starshades would be compatible with the 6 m diameter Habitable Worlds Observatory (HWO) now being planned, as well as the world’s largest telescope, the 39 m diameter European Extremely Large Telescope now being built in Chile, working as part of the HOEE, (Hybrid Observatory for Earthlike Exoplanets), and other future telescopes. We need to observe oxygen at visible wavelengths and ozone at UV.
An ISEE, positioned between a target star and the telescope, would block the starlight without blocking the exoplanets. Starshades have perfect optical efficiency, they work with any telescope, and they can block the starlight much better than the requirement, for a star >1010 times brighter than the target.
The competing technology uses a nearly perfect and perfectly stable space telescope like HWO, with an internal coronagraph, to keep the starlight away from the image of the planet. Coronagraphs have the key advantages that they are compact, testable, and have instant availability. However, tested coronagraphs have not yet met the contrast requirement. Moreover, there is no possibility of an ultraviolet coronagraph. If the extreme picometer stability and optical perfection requirements on HWO and its coronagraph could be relaxed by using it with a starshade, then HWO itself could be built at much lower cost and risk. If UV observations of exoplanets are essential, then a 35 m starshade with HWO is the only possible solution.
The HWO will be NASA’s next great observatory, and it will include a high performance coronagraph to observe exoplanets. This choice changed the landscape for the competing starshade technology. A starshade mission could still become necessary if: A. The HWO and its coronagraph cannot be built and tested as required; B. The HWO must observe exoplanets at UV wavelengths, or a 6 m HWO is not large enough to observe the desired targets; C. HWO does not achieve adequate performance after launch, and planned servicing and instrument replacement cannot be implemented; D. HWO observations show us that interesting exoplanets are rare, distant, or are hidden by thick dust clouds around the host star, or cannot be fully characterized by an upgraded HWO; or E. HWO observations show that the next step requires UV data, or a much larger telescope, beyond the capability of conceivable HWO coronagraph upgrades.
An inflatable starshade would overcome the main obstacle to starshades: their mechanical design. Starshades have never been flown, they have strict shape and edge requirements, and they must be propelled and precisely positioned. Prior designs based on discrete elements can be scaled up to the size required for HWO (35-60 m) and HOEE (100 m), but they are massive and hard to test leading to high cost and risk. Our mass budget aims for 250 kg for the 35 m HWO case, 650 kg for the 60 m case and 1700 kg for the 100 m HOEE case.We will extend our ideas and produce detailed designs and finite element models, suitable for strength, stiffness, stability, and thermal analysis. We will develop small-scale laboratory test equipment and verify solutions to issues like bonding large sheets of high-strength material into inflatable systems. Deliverable items would include mass/power budgets, strength and stiffness, and lab tests of critical items. We will update mission concepts for HWO and HOEE based on the starshade parameters.
Depending on progress with the HWO mission, starshades could be required to complete our knowledge of exoplanets. An inflatable starshade could make them possible.
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