APOD: 2026 August 5 – Spokes on Saturn’s B Ring

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

Spokes on Saturn’s B Ring

Explanation: Don’t get spooked by Saturn’s ghostly spokes! Today we feature a nearly two-hour timelapse of Saturn and its rings looping forwards and backwards. A day on Saturn is only 10 hours long, so two hours of observation covers quite a bit of its rotation. If you look closely, a ghoulish shadow appears and disappears as Saturn’s B ring rotates. Decades of observation with Voyager 2, Cassini, and Hubble show the appearance of Saturn’s spokes varies with the planet’s seasons. Like Earth, Saturn’s spin axis is tilted compared to the plane of its orbit around the Sun. During Saturn’s equinox, the rings are less tilted away from the Sun and the planet receives more evenly distributed sunlight and solar wind. Although their origin is still uncertain, Saturn’s spokes may be shadows of and reflections off of dust and ice levitating above the rings caused by electromagnetic interactions between the solar wind and the planet’s magnetic field.

Find dark skies and look up this August to witness the Perseid meteor shower uninhibited by the Moon!
Tomorrow’s picture: the COSMOS

Date:	August 5, 2026
Credit & Copyright:	Brad Croslin
Authors & editors:	Robert Nemiroff, Jerry Bonnell, Cecilia Chirenti, Keighley Rockcliffe
A service of:	ASD at NASA / GSFC, NASA Science Activation & Michigan Tech. U.

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The Paradox of Lençóis Maranhenses National Park

The coastal dune system in Lençóis Maranhenses National Park in northeastern Brazil is among the most surreal landscapes on Earth. At first glance, the park looks like a desert, but it is far from it. This place receives about 125 centimeters (50 inches) of rain per year—slightly more than Seattle and double what falls in London. 

The result is a paradox: rows of sparkling white quartz dunes, some rising 30 meters (100 feet), soar over a mosaic of blue and green freshwater lagoons. The park’s name stems from the Portuguese word lençóis, meaning “bedsheets,” a reference that makes the most sense when the park is viewed from afar. From that perspective, the sweeping curves of the largest coastal dune field in South America resemble a rumpled, white bedsheet.

These Landsat 9 images were captured in June 2026, around the time when lagoon water levels typically peak. The partially impermeable layer of bedrock and clay beneath the sand prevents the lagoons from draining during the wet season. However, as rains subside between August and November, the water table falls, and by December, most of the lagoons dry up.

The dune field, a tan area within an expanse of green, is the centerpiece of the park. It spans about 900 square kilometers (350 square miles), roughly the size of New York City. From above, shallower lagoons appear light blue, often taking on turquoise or aquamarine hues as sunlight reflects off the sand below. Deeper lagoons are darker, a result of the deeper water absorbing more red, yellow, and green wavelengths, leaving mostly blue light to scatter back. Suspended sediment, microscopic algae, and dissolved organic matter also contribute to the array of colors, giving some lagoons greener and browner tones.                                    

Green vegetation surrounds the dune field, which sits at the intersection of three Brazilian biomes: the Amazon rainforest to the west, the tropical wooded savannas of the Cerrado to the south, and the dry shrublands and thorn forests of the Caatinga to the east. Closest to the dunes are mangroves and restinga forests, ecosystems well adapted to sandy, coastal soils.

The dune field exists because of the rare convergence of geologic and climatic conditions. Rivers, including the Mearim and Parnaíba, deliver the key ingredient—quartz sand—to this unusually flat portion of the Maranhão coastline in massive quantities. It has accumulated here over the past few hundred thousand years driven in part by fluctuating sea levels and shoreline transgression and regression. Persistent easterly trade winds have also played a critical role. During the dry season, winds often reach at least 50 kilometers per hour, fast enough to build the dunes and push them westward at a pace of roughly 4 to 25 meters per year. That is fast for sand dunes, though not the fastest in the world. Satellites have tracked small barchan dunes in Namibia’s Sperrgebiet region moving at rates exceeding 80 meters per year.

Landsat images, meanwhile, show the dune field at Lençóis Maranhenses has extended westward by about 0.5 kilometers between 1986 and 2026 in some areas due to the conveyor belt of dunes running inland from the coastline. The nearly constant movement of sand prevents vegetation from becoming established across much of the dune field.

UNESCO declared the park a World Heritage site in 2024, citing its remarkable geology and rich biodiversity. The park is home to more than 850 documented species, including fish, birds, reptiles, mammals, and phytoplankton. Among them are four endangered species, including the neotropical otter, West Indian manatee, scarlet ibis, and oncilla (a type of wild cat). Among the lagoons’ most remarkable inhabitants are the trahira (Hoplias malabaricus), a predatory fish species with large canine-like teeth. During the dry season, it burrows far enough under the sand to find damp mud, where it enters a dormant state, emerging after the rains to hunt insects and other fish.

NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.

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References & Resources

• Atlas Obscura (2020, July 16) The Brazilian Desert That Turns Into a Thousand Lagoons. Accessed August 4, 2026.
• C.M. de M. Luna, M. (2011) Model for the genesis of coastal dune fields with vegetation. Geomorphology, 129(3-4), 215-224.
• CNN (2022, March 9) The unknown and otherworldly landscape of Brazil’s Lençóis Maranhenses National Park. Accessed August 4, 2026.
• Global Alliance of National Park (2026) Lencois Maranhenses National Park. Accessed August 4, 2026.
• Google Arts & Culture Lençóis Maranhenses National Park, Brazil. Accessed August 4, 2026.
• Luís Silva dos Santos, A., et al. (2019) Modelling Dunes from Lençóis Maranhenses National Park (Brazil): Largest dune field in South America. Scientific Reports, 9(7434).
• Marques, M., et al. (2015) Coastal plain forests in southern and southeastern Brazil: ecological drivers, floristic patterns and conservation status. Brazilian Journal of Botany, 38, 1–18.
• Miranda, J.P., et al., (2012) Reptiles from Lençóis Maranhenses National Park, Maranhão, northeastern Brazil. ZooKeys, 246, 51-68.
• National Geographic (2010, July) A Sea of Dunes. Accessed August 4, 2026.
• Parteli, E.J.R. (2021) Profile measurement and simulation of a transverse dune field in the  Lençóis Maranhenses. Accessed August 4, 2026.
• Revista pesquisa fapesp (2013) The secrets of the Lençóis Maranhenses. Accessed August 4, 2026.
• Smithsonian Magazine (2014, June 20) How Do Thousands of Clear Blue Lagoons End Up In These Brazilian Sand Dunes? Accessed August 4, 2026.
• UNESCO (2024) Lençóis Maranhenses National Park. Accessed August 4, 2026.

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NASA Will Attempt to Observe Rocket Part’s Lunar Impact

Using ground-based telescopes and space-based assets, NASA and SpaceX are tracking a used Falcon 9 upper stage from a commercial mission expected to impact the Moon on Wednesday, Aug. 5, near the Einstein and Bell craters. The impact poses no danger to Earth and NASA scientists are planning to collect lunar data from the event and refine techniques for tracking objects in space. 

On Jan. 15, 2025, SpaceX launched the Falcon 9 rocket and successfully deployed Firefly Aerospace’s Blue Ghost 1 lunar lander to the Moon under NASA’s CLPS (Commercial Lunar Payload Services) initiative. Solar activity and gravitational forces caused the stage’s unplanned return to the Moon. NASA and SpaceX remain in communication about the upper stage and its flight path.

Independent astronomers first identified the trajectory using publicly available data. NASA’s Center for Near Earth Object Studies at the agency’s Jet Propulsion Laboratory in Southern California, which tracks natural objects that could pose hazards to Earth, later confirmed the stage has a 100% chance of impacting the Moon. NASA will continue tracking it as part of training operations.

Because the Moon has no atmosphere to slow incoming objects, it is struck by meteoroids daily. Human‑made object impacts are far less common but do occur. The rocket stage is expected to create a crater about 60 feet wide and 12 feet deep and throw dust and rock outward as ejecta. For comparison, a meteoroid with the same energy as the upper stage hits the Moon about every six days, so the lunar surface is constantly absorbing impacts with the same force. Despite the disturbance, observing impacts gives scientists valuable insight by revealing how ejecta plumes behave, helping to understand the Moon’s geology and refine models that guide future exploration and science missions.

The impact will not be visible to the naked eye on Earth, but NASA will attempt to observe it in real time. The Meteoroid Environments Office at the agency’s Marshall Space Flight Center in Huntsville, will use ground‑based telescopes to image the impact; however, weather and lighting conditions may make viewing difficult.

Additionally, NASA’s Lunar Reconnaissance Orbiter and the ShadowCam instrument aboard South Korea’s Korea Pathfinder Lunar Orbiter will look for chances to image the site before and after the impact. Image availability will depend on lighting, orbital timing, and spacecraft position, and it may take several days to receive imagery. Any data collected will help scientists better understand artificial impacts and their exploration implications.

Although unplanned in this instance, disposing of upper stages on the lunar surface is a technically accepted and safe method and, in some cases, can be the only practical option for missions in low lunar orbit. Many operators choose controlled impacts because they provide predictable and trackable end of life outcomes.

NASA is committed to debris mitigation and demonstrating responsible disposal practices that safeguard Earth, its orbital environment, and other planetary bodies while enabling discoveries that deepen our understanding of the solar system and benefit humanity.

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NASA’s PUNCH Sharpens Solar Storm Forecasting in First Test

Using continuous imagery from NASA’s PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission, scientists predicted the near-Earth arrival of a solar eruption to within 30 minutes in an initial proof of concept test. The results, presented Tuesday at the Committee on Space Research Scientific Meeting and under review at the journal Space Weather, could revolutionize the way Earth-impacting storms are forecasted.

“We thought PUNCH would be good at this, but it’s a stunning result,” said Craig DeForest, principal investigator for PUNCH at Southwest Research Institute’s Solar System Science and Exploration Division in Boulder, Colorado. “To put it in perspective, this could be the space weather equivalent of going from a steam engine to a modern internal combustion engine.”

Solar storms are caused by huge explosions of material off the Sun called coronal mass ejections. Forecasting when the ejections will reach Earth is key for mitigating their impacts on power grids, satellites, and astronauts. However, until recently, coronal mass ejections could not continuously be tracked for much of their journey across the solar system.

That changed in 2025 with the launch of the PUNCH mission, which uses four spacecraft in low Earth orbit to make continuous 3D observations of the inner solar system. Before PUNCH, coronal mass ejections could only be seen as they traversed one-fifth the way from the Sun to Earth, leaving scientists to guess what happened over the rest of the distance. With PUNCH’s wider field-of-view, scientists can now routinely track the solar explosions nearly all the way to Earth, capturing a new image every four minutes.

Scientists used data from a coronal mass ejection that left the Sun on May 31, 2025, to retroactively test if they could improve forecast modeling. Scientists input the images into a computer model, which analyzed the leading edge of the coronal mass ejection over time. As it moved and evolved across the inner solar system, the model used the coronal mass ejection’s speed and geometry to calculate when it would reach Earth.

Twelve hours after the coronal mass ejection left the Sun, the model settled on a final prediction showing the storm would arrive eight hours later. That predicted arrival time was ultimately accurate to within a half hour, making it 10 times better than currently used methods, which only provide a 5-hour window. In addition, the model itself revealed when the estimate had stabilized, so that a space weather forecaster would be able to predict the arrival time with confidence.

“We accomplished an order of magnitude better result than the state-of-the-art method with a really basic process, just informed by the fact that the coronal mass ejection could be tracked continuously across the solar system,” DeForest said.

These first results demonstrate the power of PUNCH’s wide-field imagery to track the solar events as they travel out from the Sun. Ultimately, the scientists think that with more refined PUNCH data and better models, they could be able to forecast coronal mass ejection arrival times even further in advance.

Beyond space weather forecasting, the images also help scientists glean new insights on coronal mass ejections. The high-resolution images allowed the scientists to see new structures in coronal mass ejections, revealing that the clouds of material are clumpier than previously thought and continue to evolve as they cross the solar system.

The PUNCH data is also helping scientists better understand how plasma, the solar material launched by coronal mass ejections, moves across space. This information can help astrophysicists better understand plasma’s behavior across the galaxy, such as in star-forming regions where it is nearly impossible to study on small scales.

Southwest Research Institute, based in San Antonio, leads the PUNCH mission and operates the mission’s four spacecraft from its facilities in Boulder. The mission is managed by Space Science Mission Operations at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, for the Science Mission Directorate at the agency’s headquarters in Washington.

By Mara Johnson-Groh
NASA’s Goddard Space Flight Center, Greenbelt, Md.

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