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By NASA
Explore This Section Earth Earth Observer Editor’s Corner Feature Articles Meeting Summaries News Science in the News Calendars In Memoriam Announcements More Archives Conference Schedules Style Guide 21 min read
A Decade of Global Water Cycle Monitoring: NASA Soil Moisture Active Passive Mission
Introduction
The NASA Soil Moisture Active Passive (SMAP) mission, launched in 2015, has over 10 years of global L-band radiometry observations. The low frequency [1.4 GHz frequency or 21 cm (8 in) wavelength] measurements provide information on the state of land surfaces in all weather conditions – regardless of solar illumination. A principal objective of the SMAP mission is to provide estimates of surface soil moisture and its frozen or thawed status. Over the land surface, soil moisture links the water, energy, and carbon cycles. These three cycles are the main drivers of regional climate and regulate the functioning of ecosystems.
The achievement of 10 years in orbit is a fitting time to reflect on what SMAP has accomplished. After briefly discussing the innovative measurement approach and the instrument payload (e.g., a radiometer and a regrettably short-lived L-band radar), a significant section of this article is devoted to describing the mission’s major scientific achievements and how the data from SMAP have been used to serve society (e.g., applied sciences) – including SMAP’s pathfinding role as Early Adopters. This content is followed by a discussion of how SMAP has dealt with issues related to radio frequency interference in the L-Band region, a discussion of the SMAP data products suite, future plans for the SMAP active–passive algorithm, and a possible follow-on L-band global radiometry mission being developed by the European Union’s Copernicus Programme that would allow for data continuity beyond SMAP. This summary for The Earth Observer is excerpted from a longer and more comprehensive paper that, as of this article’s posting, is being prepared for publication in the Proceedings of the Institute of Electrical and Electronics Engineers (IEEE).
SMAP Measurement Approach and Instruments
The SMAP primary and operating instrument is the L-band radiometer, which collects precise surface brightness temperature data. The radiometer includes advanced radio frequency interference (RFI) detection and mitigation hardware and software. The radiometer measures vertical and horizontal polarization observations along with the third and fourth Stokes parameters (T3 and T4) of the microwave radiation upwelling from the Earth. The reflector boom and assembly, which includes a 6 m (20 ft) deployable light mesh reflector, is spun at 14.6 revolutions-per-minute, which creates a 1000 km (621 mi) swath as the SMAP satellite makes its Sun-synchronous orbit of the Earth – see Figure 1. This approach allows coverage of the entire globe in two to three days with an eight-day exact repeat. The radiometer instrument is calibrated monthly by pointing it to the deep sky.
Figure 1. An artist’s rendering of the SMAP Observatory showing both the radiometer and radar. Figure credit: NASA/Jet Propulsion Laboratory/California Institute of Technology The original SMAP instrument design included a companion L-band radar, which operated from April through early July 2015, acquiring observations of co- and cross-polarized radar backscatter at a spatial resolution of about 1 km (0.6 mi) with a temporal revisit of about three days over land. This data collection revealed the dependence of L-band radar signals on soil moisture, vegetation water content, and freeze thaw state. The radar transmitter failed on July 7, 2015. Shortly thereafter, the radar receiver channels were repurposed to record the reflected signals from the Global Navigation Satellite System (GNSS) constellation in August 2015, making SMAP the first full-polarimetric GNSS reflectometer in space for the investigation of land surface and cryosphere.
Scientific Achievements from a Decade of SMAP Data
A decade of SMAP soil moisture observations have led to a plethora of scientific achievements. The data have been used to quantify the linkages of the three main metabolic cycles (e.g., carbon, water, and energy) on land. They have also been used to improve drought assessments and flood prediction as well as the accuracy of numerical weather prediction (NWP) models. They are also used to measure liquid water and thickness of ice sheets, and sea surface salinity. The subsections that follow describe how SMAP data are being put to use in myriad ways that benefit society.
Quantifying Processes that Link the Terrestrial Water, Energy, and Carbon Cycles
The primary SMAP science goal is to develop observational benchmarks of how the water, energy, and carbon cycles link together over land. Soil moisture is the variable state of the land branch of the water cycle. It links the water cycle to the energy cycle through limiting latent heat flux – the change in energy as heat exchanges when water undergoes a phase change, such as evapotranspiration at the land–atmosphere interface. Soil moisture also links the water and carbon cycles, which is evident through plant photosynthesis. SMAP global observations of soil moisture fields, in conjunction with remote sensing of elements of the energy and carbon cycles, can reveal how these three cycles are linked in the real world as a benchmark for weather and Earth system models.
Photosynthesis is down-regulated by both the deficit in water availability and the lack of an adequate amount of photosynthetically active radiation. Global maps reveal how soil moisture and light regulate photosynthesis – see Figure 2. These benchmark observational results can be used to assess how Earth system models link to the three main metabolic cycles of the climate system.
Figure 2. Observed regulation of photosynthesis by water availability [left] and light availability [right]. Blue denotes greater limitation. Photosynthesis rates for both maps determined using solar-induced fluorescence (SIF) measurements (mW/m2 nm sr) from the Tropospheric Ozone Monitoring Instrument (TROPOMI) on the European Union’s Copernicus Sentinel-5P mission. Water availability was determined using soil moisture (SM) measurements from the Soil Moisture Active Passive (SMAP) mission. Light availability was determined using measurements of photosynthetically active radiation (PAR) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua platforms. The resulting maps show the model slope (mW/m2/nm/sr) of the estimated SIF-SM relationship in the water-limited regime [left] and the model slope (10-3/nm/sr) of estimated SIF-PAR relationship in the light-limited regime [right]. Figure credit: Jonard et al (2022) in Biogeosciences Development of Improved Flood Prediction and Drought Monitoring Capability
SMAP products have also been widely used in applied sciences and natural hazard decision-support systems. SMAP’s observation-based soil moisture estimates offer transformative information for managing water-related natural hazards, such as monitoring agricultural drought – defined as a persistent deficit in soil moisture – and flood volumes – defined as the landscape’s water absorption capacity during precipitation events. The SMAP project produces a parallel, near-real-time data stream that is accessed by a number of federal and state agencies in decision-support systems related to drought monitoring, food security, and landscape inundation and trafficability.
Enhancing Weather and Climate Forecasting Skill
SMAP’s enhancement of numerical weather prediction, model skill, and reduction of climate model projection uncertainties is based on the premise of the contribution of solar energy to weather and climate dynamics. Soil moisture has a strong influence on how available solar energy is partitioned into components (e.g., sensible heat flux versus latent heat flux) over land. The influence propagates through the atmospheric boundary layer and ultimately influences the evolution of weather.
To give an example, land surface processes can affect the evolution of the U.S. Great Plains low-level jets (GPLLJs). These jets drive mesoscale convective weather systems. Previous studies have shown that GPLLJs are sensitive to regional soil moisture gradients. Assimilation of SMAP soil moisture data improves forecasts of weakly synoptically forced or uncoupled GPLLJs compared to forecasts of cyclone-induced coupled GPLLJs. For example, the NASA Unified Weather Research and Forecasting Model, with 75 GPLLJs at 9 km (5.6 mi) resolution both with and without SMAP soil moisture data assimilation [SMAP data assimilation (DA) and no-DA respectively], shows how the windspeed mean absolute difference between SMAP DA and no-DA increase approximately linearly over the course of the simulation with maximum differences at 850 hPa (or mb) for the jet entrance and core – see Figure 3.
Figure 3. The impact of adding soil moisture data [SMAP data assimilation (DA) minus no-DA] to a model simulation from theNASA Unified Weather Research and Forecasting Model (NU-WRF)) of the Great Plains Low Level Jet (GPLLJ). The results show the mean over 75 independent GPLLJ events. The plots correspond to wind speed difference with height (y-axis) and time (hours on x-axis). The panels are for jet entrance [left], jet core [middle] and jet exit [right]. Soil moisture data assimilation enhances the intensity of the simulated GPLLJ. The stippling corresponds to 99% statistical confidence. Figure credit: Ferguson (2020) in Monthly Weather Review Measuring Liquid Water Content and Thickness of Ice Sheets
The mass loss of Greenland and Antarctica ice sheets contributes to sea-level rise – which is one of the most impactful and immediate damaging consequences of climate change. The melt rates over the last few years have raised alarm across the globe and impact countries with coastal communities. The cryosphere community has raised a call-to-action to use every observing system and model available to monitor the patterns and rates of land ice melt.
Surface melt affects the ice cap mass loss in many ways: the direct melt outflow from the ablation zone of the Greenland ice sheet, the structural change of the percolation zone of the Greenland ice sheet, changes in the melt water retention and outflow boundaries, changes in the structure of the Antarctic ice shelves, and destabilization of the buttressing of the glacier outflow through various processes (e.g., hydrofracturing and calving). The long-term climate and mass balance models rely on accurate representation of snow, firn, and ice processes to project the future sea level.
The SMAP L-band radiometer has relatively long wavelength [21 cm (8 in)] observations compared to other Earth-observing instruments. It enables the measurement of liquid water content (LWC) in the ice sheets and shelves as it receives the radiation from the deep layers of the snow/firn/ice column. Relatively high LWC values absorb the emission only partially, making the measurement sensitive to different liquid water amounts (LWA) in the entire column. Figure 4 shows the cumulative LWA for 2015–2023 based on SMAP measurements.
Figure 4. Total annual sum of SMAP daily liquid water amount (LWA) for 2015–2023. The black solid line on each map represents grid edges, and the grey color mask inside the ice sheet indicates melt detections by decreasing brightness temperature. Figure Credit: Andreas Colliander [Finnish Meteorological Institute]. The SMAP L-band radiometer has also been used to derive the thickness of thin sea ice [Soil Moisture and Ocean Salinity (SMOS) mission have been recalibrated to SMAP, using the same fixed incidence angle. The data show strong agreement and demonstrate clear benefits of a combined dataset. The L-band thin ice thickness retrievals provide a useful complement to higher-resolution profiles of thicker ice obtained from satellite altimeters (e.g. ESA’s CryoSat-2 and NASA’s Ice, Clouds and land Elevation Satellite–2 missions).
Extending and Expanding the Aquarius Sea Surface Salinity Record
The joint NASA/Argentinian Aquarius/Satélite de Aplicaciones Científicas (SAC)-D (Aquarius), which operated from 2011–2015, used an L-band radiometer and an L-band scatterometer to make unprecedented monthly maps of global sea surface salinity at 150-km (93-mi) resolution. The SMAP L-band radiometer has not only extended the sea surface salinity record in the post-Aquarius period, it has also increased the spatial resolution and temporal frequency of these measurements because of its larger reflector and wider swath. The increased resolution and revisit allow new and unprecedented perspectives into mixing and freshwater events, coastal plume tracking, and other more local oceanic features.
Providing New Perspectives on Global Ecology and Plant Water Stress
The L-band vegetation optical depth (VOD) – which is related to water content in vegetation – has been retrieved simultaneously with soil moisture using SMAP’s dual-polarized brightness temperatures and is being used to better understand global ecology. Water in above-ground vegetative tissue attenuates and thus depolarizes surface microwave emission, and VOD quantifies this effect. SMAP can provide global observations of VOD in all weather conditions with a two to three day temporal frequency. Changes in VOD indicate either plant rehydration or growth. Ecologists benefit from this new ecosystem observational data, which augments optical and near-infrared vegetation indices [e.g., leaf area index (LAI)] and has a higher temporal frequency that is not affected by clouds and does not saturate as rapidly for dense vegetation.
Examples of how the data have been used include deciphering the conditions when vegetation uptakes soil water only for rehydration (i.e., VOD increase with no LAI change) compared to plant growth (i.e., increase in both VOD and LAI). The applications of VOD are increasing and the ecology community views this product as a valuable additional perspective on soil–plant water relations.
At the moment, this measurement has no ground-based equivalent. Therefore, field experiments with airborne instruments and ground sampling teams are needed to firmly establish the product as a new observational capability for global ecology.
Applied Science Collaboration: SMAP Observations Serving Society
The SMAP project has worked with the NASA Earth Science Division Applied Sciences Program (now known as Earth Science to Action) and the natural hazards monitoring and forecasting communities for pre- and post-launch implementation of SMAP products in their operations. In some operational applications, for which long-term data continuity is a requirement, the SMAP data are still used for assessment of current conditions, as well as research and development.
The Original Early Adopters
Prior to its launch, the SMAP mission established a program to explore and facilitate applied and operational uses of SMAP mission data products in decision-making activities for societal benefit. To help accomplish these objectives, SMAP was the first NASA mission to create a formal Applications Program and an Early Adopter (EA) program, which eventually became a requirement for all future NASA Earth Science directed satellite missions. SMAP’s EA program increases the awareness of mission products, broadens the user community, increases collaboration with potential users, improves knowledge of SMAP data product capabilities, and expedites the distribution and uses of mission products after launch.
SMAP Data in Action
Several project accomplishments have been achieved primarily through an active continuous engagement with EAs and operational agencies working towards national interests. SMAP soil moisture data have been used by the U.S. Department of Agriculture (USDA) for domestic and international crop yield applications. For example the USDA’s National Agricultural Statistics Service (NASS) conducts a weekly survey of crop progress, crop condition, and soil moisture condition for U.S. cropland. NASS surveys and publishes state-level soil moisture conditions in the NASS Crop Progress Report.
The traditional field soil moisture survey is a large-scale, labor-intensive data collection effort that relies heavily on responses from farmers, agricultural extension agents and/or other domain experts for field observations. One weakness of these observations is that they are based on subjective assessments rather than quantitative measures and can lead to spatial inconsistency based on the human responses from the respective counties. Moreover, the NASS Crop Progress Reports do not provide specific geolocation information for the assessed soil moisture conditions – which are extremely useful metadata to provide to data users. NASS implemented the use of SMAP observations in their weekly reports during the growing period (March–November). SMAP maps estimated root-zone soil moisture for the week of November 14–20, 2022, over NASS Pacific (California and Nevada) and Delta (Arkansas, Mississippi and Louisiana) regional domains—see Figure 5.
Figure 5. SMAP-based soil moisture estimates for California, Nevada, Arkansas, Mississippi, and Louisiana, used by the U.S. Department of Agriculture’s (USDA) National Agricultural Statistics Service (NASS) in their weekly report covering November 14–20, 2022. These data are available for selected states at the NASS website linked in the text. Figure Credit: NASS SMAP Radio Frequency Interference Detection and Mitigation
Although SMAP operates within the protected frequency allocation of 1400–1427 MHz, the radiometer has been impacted by radio frequency interference over the mission lifetime. Unauthorized in-band transmitters as well as out-of-band emissions from transmitters operating adjacent to the allocated spectrum have been observed in SMAP measurements since its launch. The previously launched SMOS and Aquarius radiometers provide evidence of global RFI at L-band. Consequently, SMAP was designed to incorporate a novel onboard digital detector on the back end to enable detection and filtering of RFI. The radiometer produces science data in time and frequency, enabling the use of multiple RFI detection methods in the ground processing software.
On-orbit data demonstrate that the RFI detection and filtering performs well and improves the quality of SMAP brightness temperature measurements. The algorithms are most effective at filtering RFI that is sparse in time and frequency, with minimal impact on the noise equivalent delta temperature (NEDT) – a measure of the radiometer sensitivity. Some areas of the globe remain problematic as RFI that is very high level and persistent results in high percentages of data loss due to removal of contaminated data. A global map of RFI detection rate for January 2025 shows a large contrast between Eastern and Western Hemispheres and between Northern and Southern Hemispheres – see Figure 6. Regions of isolated RFI and severe RFI correspond to populated areas. A detection rate of 100% means all pixels are flagged and removed, resulting in data loss. Analysis of spectral information reveal many sources are likely terrestrial radar systems; however, many wideband, high-level sources and low-level, non-radar sources also persist. Over areas of geopolitical conflict, the time-frequency data show interference covering the entire radiometer receiver bandwidth.
Figure 6. Percentage of pixels on a 0.25° grid for January 2025 that have been flagged for removal by the Soil Moisture Active Passive radio frequency interference detection algorithms. Figure Credit: Priscilla N. Mohammed [GSFC] The RFI challenge is further addressed through official spectrum management channels and formal reports that include the geolocated coordinates of sources, interference levels, frequency of occurrence during the observed period, and spectral information – all of which aid field agents as they work to identify potential offenders. Reports are submitted to the NASA Spectrum office and then forwarded to the country of interest through the Satellite Interference Reporting and Resolution System.
SMAP Science Data Products
The current suite of SMAP science data products is available in the Table. The principal data products are grouped in four levels designated as L1–4. The L1 products are instrument L-band brightness temperature in Kelvin and include all four Stokes parameters (i.e., horizonal and vertical polarization as well as third and fourth Stokes). Both 6:00 AM equatorial crossing (descending) and 6:00 PM equatorial crossing (ascending data) are contained in the products. The user has access to quality flags of the conditions under which measurements are available for each project. The L1B products are time-ordered and include fore and aft measurements. L1C products are on the Equal-Area Scalable Earth V2 (EASE2) grid with polar and global projections. L2 data products are geophysical retrievals (i.e., soil moisture, VOD, and binary freeze/thaw classification on a fixed Earth grid). The L2 half-orbit products are available to the public within a day of acquisition. L3 products are daily composites and include all half-orbits for that day.
The SMAP project also produces L4 data that are the result of data assimilation. The L4 products take advantage of other environmental observations, such as precipitation, air temperature and humidity, radiative fluxes at the land surface, and ancillary land use and soil texture information, to produce estimates of surface [nominally 0–5 cm (0–2 in)] and subsurface (e.g., root-zone up to a meter) soil moisture. The data assimilation system is a merger of model and measurements and hence resolves the diurnal cycle of land surface conditions. The data assimilation system also provides estimates of surface fluxes of carbon, energy, and water, such as evaporation, runoff, gross primary productivity (GPP), and respiration. The difference between GPP and respiration is the net ecosystem exchange, which is the net source/sink of the carbon cycle over land.
The SMAP suite of products also include near-real-time (NRT) brightness temperature and soil moisture products for use in operational weather forecast applications. The NRT product targets delivery to users within three hours of measurement acquisition. The NRT uses predicted SMAP antenna pointing (instead of telemetry) and model predicted ancillary data (soil temperature) in order to support operational centers that require more than three hours of data products for updating weather forecast models. To date SMAP has met its required and target (for NRT) latency requirements.
Two other data projects merge synergistically with other (colocated) satellite measurements. The SPL2SMAP_S merges SMAP L-band radio brightness measurements with C-band synthetic aperture radar (SAR) measurements from the ESA Copernicus Sentinel-1 mission. The SAR data have high resolution and allow the generation of 1 and 3 km (0.62 and 1.8 mi) merged surface soil moisture estimates. The high resolution soil moisture information, however, is only available when there is coincident SMAP and Sentinel-1 measurements. The refresh rate of this product is limited and can be as long as 12 days.
The merged SMOS–SMAP passive L-band radiometry data allows the generation of global, near daily surface soil moisture estimates, which are required to resolve fast hydrologic processes, such as gravity drainage and recharge flux. These parameters are only partially resolved with the SMAP, with a two to three day data refresh rate. This product interpolates the multi-angular SMOS data to the SMAP 40º incident angle and uses all SMAP algorithms, including correction of waterbody impact on SMAP brightness temperature, and ancillary data for geophysical inversions to soil moisture and VOD, ensuring consistency. The combined SMAP–SMOS data product may not be available daily across locations, such as Japan, parts of China, and the Middle East, where RFI affects data collection.
Table. Soil Moisture Active Passive suite of science products are available through the National Snow and Ice Data Center, one of NASA’s Distributed Active Archive Centers.
Product Type Product description Resolution (Gridding) Granule Extent SPL1BTB Geolocated, calibrated brightness temperature in time order 36 km Half Orbit SPL1CTB_E Backus-Gilbert interpolated, calibrated brightness temperature in time order (9 km) Half Orbit SPL1CTB Geolocated, calibrated brightness temperature on Equal-Area Scalable Earth V2 (EASE2) grid 36 km Half Orbit SPL1CTB_E Backus-Gilbert interpolated, calibrated brightness temperature on EASE2 grid (9 km) Half Orbit SPL2SMP Radiometer soil moisture and vegetation optical depth 36 km Half Orbit SPL2SMP_E Radiometer soil moisture and vegetation optical depth based on SPL1CTB (9 km) Half Orbit SPL2SMAP_S SMAP radiometer/Copernicus Sentinel-1 soil moisture 3 km Sentinel-1 SPL3SMP Daily global composite radiometer soil moisture and vegetation optical depth based on SPL1CTB 36 km Daily–Global SPL3SMP_E Daily global composite radiometer soil moisture and vegetation optical depth based on SPL1CTB_E (9 km) Daily–Global SPL3FTP Daily composite freeze/thaw state based on SPL1CTB 36 km Daily–Global SPL3FTP_E Daily composite freeze/thaw state based on SPL1CTB_E (9 km) Daily–Global SPL4SMAU Surface and Root Zone soil moisture 9 km 3 hours – Global SPL4CMDL Carbon Net Ecosystem Exchange 9 km Daily–Global SPL1BTB_NRT Near Real Time Geolocated, calibrated brightness temperature in time order 36 km Half Orbit SPL2SMP_NRT Near Real Time Radiometer soil moisture 36 km Half Orbit L2/L3 SMOS SM SMOS soil moisture and VOD based on SMAP algorithms (9 km) Half Orbit/Daily Global Future Directions for the SMAP Active–Passive Algorithm
Although the SMAP radar failed not long after launch, the data that were collected have been used to advance the development of the SMAP Active–Passive (AP) algorithm, which will be applied to the combined SMAP radiometer data and radar data from the NASA–Indian Space Research Organisation (ISRO) Synthetic Aperture Radar [NISAR] mission, a recently-launched L-Band Synthetic Aperture mission to produce global soil moisture at a spatial resolution of 1 km (0.62 mi) or better. The high resolution product can advance applications of SMAP data (e.g., agricultural productivity, wildfire, and landslide monitoring).
Data Continuity Beyond SMAP
A forthcoming mission meets some – but not all – of the SMAP measurement requirements and desired enhancements. The European Union’s Copernicus Program Copernicus Imaging Microwave Radiometer (CIMR) mission is a proposed multichannel microwave radiometry observatory that includes L-band and four other microwave channels sharing a large mesh reflector. The mesh reflector is similar to the one that is used on SMAP, but larger. The successful SMAP demonstration of rotating large deployable mesh antennas for Earth observations has been useful to the CIMR design.
In terms of RFI detection capability, CIMR will also use an approach that is similar to SMAP. With regard to instrument thermal noise (NEDT) and data latency, CIMR meets or comes close to the next-mission desired characteristics and equals or exceeds SMAP in most of the attributes. The native L-band resolution of CIMR is ~60 km (37 mi); however, the measurements are coincident and higher-resolution measurements in this configuration allow reconstruction of L-band radiometry at higher resolution than CIMR’s L-band. It may be possible to combine the L- and C-bands and achieve a reconstructed ~15 km (9 mi) L-band product based on the coincident and overlapping measurements. A refresh rate of one day is possible with the wide-swath characteristic of CIMR.
CIMR is currently in development; the first version, CIMR-1A, is expected to launch within this decade and the second version, CIMR-1B, in the mid 2030s. Since the Copernicus program supports operational activities (e.g., numerical weather prediction), the program includes plans for follow-on CIMR observatories so that the data record will be maintained without gaps in the future.
Conclusions
The SMAP mission was launched in 2015 and has produced over 10 years of science data. Because of its unique instrument and operating characteristics, the global low-frequency microwave radiometry with the SMAP observatory has resulted in surface soil moisture, vegetation optical depth, and freeze/thaw state estimates that outperform past and current products. The data have been widely used in the Earth system science community and also applied to natural hazards applications.
The Earth system science and application communities are actively using the decade-long, high-quality global L-band radiometry. The intensity and range of SMAP science data usage is evident in the number of peer-reviewed journal publications that contain SMAP or Soil Moisture Active Passive in their title or abstract and use SMAP data in the study (i.e., search: www.webofscience.com data-base). The authors acknowledge that many publications escape this particular query approach. Currently the bibliography includes over 1700 entries and over 20,000 citations spanning several elements of Earth system science, including hydrologic science and regional and global water cycle, oceanic and atmospheric sciences, cryosphere science, global ecology as well as microwave remote sensing technologies.
To Learn More About SMAP
A more comprehensive bibliography of studies published based on SMAP data products, a set of one-page SMAP science and applications highlights in standardized format, and SMAP project documents including assessment reports are all available online via the links provided.
Acknowledgements
The authors wish to acknowledge the contributions of the SMAP Science Team, the SMAP Algorithm Development Team, and the SMAP Project Office engineers and staff. All of these teams contribute to the ongoing SMAP science product generation and uses reported in this article.
Dara Entekhabi
Massachusetts Institute of Technology
darae@mit.edu
Simon Yueh
Jet Propulsion Laboratory/California Institute of Technology
simon.h.yueh@jpl.nasa.gov
Rajat Bindlish
NASA Goddard Space Flight Center
rajat.bindlish@nasa.gov
Mark Garcia
Jet Propulsion Laboratory/California Institute of Technology
mark.d.garcia@jpl.nasa.gov
Jared Entin
NASA Headquarters
jared.k.entin@nasa.gov
Craig Ferguson
NASA Headquarters
craig.r.ferguson@nasa.gov
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Earth Science View the full article
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By USH
The weight of the gods was crushing, their toil beyond endurance. Let the burden pass to humankind! So speak the oldest verses carved into clay, a fragment from the Atrahasis tale of Mesopotamia. Yet what if these divine figures were not simply legends? What if the stories hint at something far older and stranger than we have allowed ourselves to believe? The name Anunnaki comes from the etched symbols of Sumerian records, their lines recounting the deeds of deities who shaped the world and watched over the Earth.
From the cradle of ancient Mesopotamia comes a story older than any empire, etched into clay tablets and whispered through time: the tale of the Anunnaki. Were they gods, symbols, or something far stranger visitors from beyond the stars who shaped human civilization? The myths of Sumer speak of creation, rebellion, giants, and a great flood. But when paired with the ancient astronaut theory, these legends take on a new dimension, one that could rewrite human history.
Who were the Anunnaki? In the ancient Sumerian texts of Mesopotamia, they are described as the offspring of An, the sky god, and Ki, the earth goddess. Their names appear across the Atrahasis epic, the Enuma Elish, the Epic of Gilgamesh, and the Sumerian King List, etched into clay tablets more than 4,000 years ago.
To mainstream historians, the Anunnaki are mythological gods. Yet in the ancient astronaut theory, they were real beings, extraterrestrial visitors who shaped early civilization.
Author Zecharia Sitchin popularized the idea that the Anunnaki came from Nibiru, a hidden “twelfth planet” on a long, elliptical orbit. According to his interpretation of Sumerian records, the Anunnaki faced an environmental crisis. Their planet’s atmosphere was failing, and the solution they sought was gold, which could be ground into particles and suspended as a shield.
This quest for survival brought them to Earth more than 400,000 years ago. They mined resources, altered life, and may even have engineered humanity itself.
The tablets describe how the lesser gods, the Igigi, were forced into back-breaking labor until they rebelled. To replace them, the Anunnaki created humans.
In myth, mankind was formed from clay mixed with divine blood. In Sitchin’s interpretation, this was genetic engineering: the fusion of Anunnaki DNA with Homo erectus. The first prototype was Adamu, a name that echoes the biblical Adam.
The Sumerian “Edin,” later mirrored in the Hebrew Eden, may not have been a paradise garden but an Anunnaki laboratory outpost.
Two Anunnaki brothers shaped humanity’s destiny: Enki – the god of wisdom and waters, often seen as humanity’s ally, granting knowledge. Enlil – stern and authoritarian, seeking control and fearing that humans might grow too powerful. Their rivalry runs through Mesopotamian myth, influencing stories of divine punishment, survival, and human struggle.
Over time, some Anunnaki defied the rules and took human women as partners. Their offspring were the Nephilim, giants and “mighty men of renown.” The Book of Enoch calls their fathers the Watchers, led by Shemyaza.
According to the stories, these hybrids grew violent, corrupted the world, and became uncontrollable. The solution was drastic: a great flood to wipe the Earth clean.
The Atrahasis epic, the story of Utnapishtim in the Epic of Gilgamesh, and the biblical Noah all describe the same event: a chosen man warned by a god, a vessel built to preserve life, animals carried aboard, and birds released to find land. Humanity survived, but weaker, with shorter lifespans, and forever changed.
Supporters of the ancient astronaut theory believe the Anunnaki left traces in stone:
Mesopotamian ziggurats – described as “bonds between heaven and earth,” possibly landing platforms.
The Great Pyramid of Giza – aligned to true north, massive in scale, theorized as a power plant or beacon rather than a tomb.
Megalithic monuments worldwide – stone circles, cyclopean walls, and sacred sites possibly linked to Anunnaki influence.
The Sumerian King List also suggests a divine legacy, describing rulers with lifespans of thousands of years, perhaps evidence of semi-divine hybrids.
Mainstream archaeology sees the Anunnaki as symbolic deities, metaphors for cosmic order and human struggle. But in alternative history, they were real beings, extraterrestrial visitors from Nibiru, who shaped civilization, taught astronomy, metallurgy, agriculture, and law, and left their mark in myths and monuments that endure to this day.
Explore the mystery of the Anunnaki—Sumerian gods, Nibiru, genetic engineering, Nephilim, the Great Flood, and the ancient astronaut theory in the video below.
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By NASA
Explore This Section Science Courses & Curriculums for… STEM Educators Are Bringing… Overview Learning Resources Science Activation Teams SME Map Opportunities More Science Activation Stories Citizen Science 4 min read
STEM Educators Are Bringing Hands-On NASA Science into Virginia Classrooms
Professional learning experiences are integral to the enhancement of classroom instruction. Teachers, at the forefront of Science, Technology, Engineering, & Mathematics (STEM) education, play a key role in the advancement of STEM learning ecosystems and citizen science.
On June 24-25, 2025 – despite a major east coast heat wave – twenty-four educators from eight school districts in the Hampton Roads region of southeastern Virginia (Newport News, Hampton City, Virginia Beach City, Isle of Wight County, Poquoson City, Norfolk, York County, and Suffolk Public Schools) converged at the National Institute of Aerospace (NIA) in Hampton, VA for a professional development workshop led by experts from NASA Langley Research Center and the NASA Science Activation program’s NIA-led NASA eClips team. Developed in collaboration with another NASA Science Activation team, GLOBE (Global Learning and Observations to Benefit the Environment) Mission Earth, and with support from the Coastal Virginia STEM Hub (COVA STEM) – a “STEM learning ecosystem targeting pre-K to adult residents in Coastal Virginia” – this two-day training, also provided comprehensive resources, including lesson plans, pacing guides, classroom activities, and books, all designed for integration into Hampton Roads classrooms.
The NASA Langley team led workshop participants through a training about GLOBE, a program dedicated to advancing Earth System science through data collected by volunteer members of the public, also known as ‘citizen scientists’. GLOBE invites educators, students, and members of the public worldwide (regardless of citizenship) to collect and submit cloud, surface temperature, and land cover observations using the GLOBE Observer app – a real-time data collection tool available right on their smartphones. These observations are then used to help address scientific questions at local, regional, and global scales. Through this training, the educators participated in K-20 classroom-friendly sample lessons, hands-on activities, and exploring the GLOBE Observer app, ultimately qualifying them as GLOBE Certified Educators. Earth System science lessons, activities, and information on how to download the GLOBE Observer citizen science app are available on the GLOBE website. Similarly, NASA eClips, which focuses on increasing STEM literacy in K-12 students, provided educators with free, valuable, standards-based classroom resources such as educator guides, informational videos, engineering design packets, and hands-on activities, which are available to educators and students alike on the NASA eClips’ website. Throughout the training, educators collaborated in grade-level groups, brainstorming new ways to integrate these standards-based NASA science resources.
One educator envisioned incorporating GLOBE’s cloud resources and supportive NASA eClips videos into her energy budget unit. Others explored modifying a heat-lamp experiment to include humidity and heat capacity. One teacher enthusiastically noted in response to a GLOBE urban heat island lesson plan, “The hands-on elements are going to be really great deliverables!” The creative energy and passion for education were palpable.
The dedication of both NIA and NASA Langley to education and local community support was evident. This professional learning experience offered educators immediately-applicable classroom activities and fostered connections among NASA science, NASA eClips, the GLOBE Program, and fellow educators across district lines. One educator highlighted the value of these networking opportunities, stating, “I do love that we’re able to collaborate with our colleagues so we can plan for our future units during the school year”. Another participant commented, “This is a great program…I am going to start embedding [this] in our curriculum.”
GME (supported by NASA under cooperative agreement award number NNX16AC54A) and NASA eClips (supported by NASA under cooperative agreement award number NNX16AB91A) are part of NASA’s Science Activation Portfolio. Learn more about how Science Activation connects NASA science experts, real content, and experiences with community leaders to do science in ways that activate minds and promote deeper understanding of our world and beyond: https://science.nasa.gov/learn
GLOBE educator Marilé Colón Robles demonstrates a kinesthetic activity. Share
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Last Updated Aug 04, 2025 Editor NASA Science Editorial Team Location NASA Langley Research Center Related Terms
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By NASA
Before astronauts venture around the Moon on Artemis II, the agency’s first crewed mission to the Moon since Apollo, Mark Cavanaugh is helping make sure the Orion spacecraft is safe and space-ready for the journey ahead.
As an Orion integration lead at NASA’s Johnson Space Center in Houston, he ensures the spacecraft’s critical systems— in both the U.S.-built crew module and European-built service module—come together safely and seamlessly.
Mark Cavanaugh stands in front of a mockup of the Orion spacecraft inside the Space Vehicle Mockup Facility at NASA’s Johnson Space Center in Houston.NASA/Robert Markowitz With nearly a decade of experience at NASA, Cavanaugh currently works within the Orion Crew and Service Module Office at Johnson. He oversees the technical integration of the European Service Module, which provides power, propulsion, and life support to Orion during Artemis missions to the Moon. His work includes aligning and verifying essential systems to keeping the crew alive, including oxygen, nitrogen, water storage, temperature regulation, and spacecraft structures.
In addition to his integration work, Cavanaugh is an Orion Mission Evaluation Room (MER) manager. The MER is the engineering nerve center during Artemis flights, responsible for real-time monitoring of the Orion spacecraft and real-time decision-making. From prelaunch to splashdown, Cavanaugh will lead a team of engineers who track vehicle health and status, troubleshoot anomalies, and communicate directly with the flight director to ensure the mission remains safe and on track.
Mark Cavanaugh supports an Artemis I launch attempt from the Passive Thermal Control System console on Aug. 29, 2022, in the Orion Mission Evaluation Room at NASA’s Johnson Space Center.NASA/Josh Valcarcel Cavanaugh’s passion for space exploration began early. “I’ve wanted to be an aerospace engineer since I was six years old,” he said. “My uncle, who is also an aerospace engineer, used to take me to wind tunnel tests and flight museums as a kid.”
That passion only deepened after a fifth-grade trip from Philadelphia to Houston with his grandfather. “My dream of working at NASA Johnson started when I visited the center for the first time,” he said. “Going from being a fifth grader riding the tram on the tour to contributing to the great work done at Johnson has been truly incredible.”
Turning that childhood dream into reality did not come with a straight path. Cavanaugh graduated from Pennsylvania State University in 2011, the same year NASA’s Space Shuttle Program ended. With jobs in the space industry in short supply, he took a position with Boeing in Houston, working on the International Space Station’s Passive Thermal Control System. He later supported thermal teams for the Artemis Moon rocket called the Space Launch System, and the Starliner spacecraft that flew astronauts Butch Wilmore and Suni Williams during their Boeing Crew Flight Test mission, before a mentor flagged a NASA job posting that turned out to be the perfect fit.
He joined NASA as the deputy system manager for Orion’s Passive Thermal Control System, eventually stepping into his current leadership role on the broader Orion integration team. “I’ve been very lucky to work with some of the best and most supportive teammates you can imagine,” he said.
Mark Cavanaugh with his mother, Jennifer, in front of the Artemis I Orion spacecraft following the thermal vacuum test at the Space Environments Complex at NASA’s Neil Armstrong Test Facility in Sandusky, Ohio. Cavanaugh says collaboration and empathy were key to solving challenges along the way. “I’ve learned to look at things from the other person’s perspective,” he said. “We’re all working toward the same incredible goal, even if we don’t always agree. That mindset helps keep things constructive and prevents misunderstandings.”
He also emphasizes the importance of creative problem-solving. “For me, overcoming technical challenges comes down to seeking different perspectives, questioning assumptions, and not being afraid to try something new—even if it sounds a little ridiculous at first.”
Mark Cavanaugh riding his motorcycle on the Circuit of the Americas track in Austin, Texas. Outside of work, Cavanaugh fuels his love of speed and precision by riding one of his three motorcycles. He has even taken laps at the Circuit of the Americas track in Austin, Texas.
When he is not on the track or in the control room, Cavanaugh gives back through student outreach. “The thing I always stress when I talk to students is that nothing is impossible,” he said. “I never thought I’d get to work in the space industry, let alone at NASA. But I stayed open to opportunities—even the ones that didn’t match what I originally imagined for myself.”
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Bring NASA Science into Your Library!
Calling all librarians! NASA sponsors dozens of research projects that need help from you and the people in your community. These projects invite everyone who’s interested to collaborate with scientists, investigating mysteries from how star systems form to how our planet sustains life. You can help by making observations with your cell phone or by studying fresh data on your laptop from spacecraft like the James Webb Space Telescope. You might discover a near-Earth asteroid or a new food option for astronauts. Participants learn new skills and meet scientists and other people around the world with similar interests.
Interested in sharing these opportunities with your patrons? Join us on August 26, 2025 at 1 p.m. EST for a 1-hour online information session. A librarian and a participatory science professional will provide you with a NASA Citizen Science Librarian Starter Kit and answer all your questions. The kit includes everything you need to host a NASA Science Program for patrons of all ages.
Editable poster to advertise event Event prep guide (for the host and for the space) Community connection ideas Editable event agenda Handout for participants Scan the QR code above or go to https://shorturl.at/tKfTt to register for the session.
Kara Reiman, Librarian and Educator (Left) and Sarah Kirn, Participatory Science Strategist, NASA (Right) Share
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Last Updated Jul 21, 2025 Related Terms
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