Blue-green algae bloom in Lake Erie’s summer conditions. Unfortunately for those looking to spend summer on the water, the dominant organism in this bloom produces a toxin that “can cause liver damage, numbness, dizziness, and vomiting.” Bloom season can last from late June into October, depending on the how many nutrients get washed into the lake and when wind mixes the lake water in the fall. A new hyperspectral instrument aboard NASA’s PACE spacecraft will identify bloom species from space, helping scientists track, understand, and predict blooms like these. (Image credit: W. Liang; via NASA Earth Observatory)
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Eerie Aurora
This surreal image comes from an aurora on Halloween 2013. Photographer Ole C. Salomonsen captured it in Norway during one of the best auroral displays that year. The shimmering green and purple hues are the glow of oxygen and nitrogen in the upper atmosphere reacting to high-energy particles streaming in from the solar wind. These geomagnetic storms can disrupt GPS satellites, compromise radio communication, and even corrode pipelines, but they also create these stunning nighttime displays. (Image credit: O. Salomonsen; via APOD)
The Great Red Spot’s Cycle
First spotted by humanity in 1664, Jupiter‘s Great Red Spot is a seemingly endless storm. Strictly speaking, there is debate as to whether observations prior to 1831 were of the same storm, but there’s no denying that the storm has raged unabated since regular observations began in the first half of the nineteenth century. Despite its longevity, the Great Red Spot is not unchanging. Overall, its major axis is shrinking, making the storm more circular over time. The storm also has a 90-day cycle in which its size, shape, and brightness vary, as seen below. Researchers note that the changes are relatively subtle — at least to the eye — but now that they’ve been identified, it may be possible to use amateur astronomers’ data to track these variations more closely. (Image credits: GRS – K. Gill/NASA, snapshots – A. Simon et al.; research credit: A. Simon et al.; via Gizmodo)
Over a 90 day cycle, Jupiter’s Great Red Spot oscillates in size, shape, and other characteristics. 
Self-Cleaning With Salt Critters
Even freshwater contains trace salts and minerals that cause scaly buildups as they evaporate. Getting rid of the scale usually requires toxic chemicals and/or lots of scrubbing, neither of which are desirable at the industrial level. At the same time, we’re extremely limited in the amount of freshwater that we have available; only about 1% of Earth’s water is liquid and fresh. If we could use salt water in more industrial processes, that would preserve freshwater for drinking and agriculture. But how do we tackle the scaly buildup?
(A) On microtextured surfaces, salt from evaporating drops can work its way into the gaps, destroying the superhydrophobicity of the surface. (B) In contrast, nanotextured surfaces give the salt nowhere to adhere, resulting in “salt critters” that grow upward and detach. Enter “salt critters.” Researchers found that when salt water evaporated from microtextured surfaces designed to shed water, salt would eventually build up in the gaps, breaking the hydrophobic effect and allowing scale to build up. In contrast, a nanotextured surface left nowhere for the salt to adhere. On these surfaces, evaporating salt water built jellyfish-like salt critters that rose from the surface and, eventually, broke off and rolled away, leaving the surface pristine. (Image credit: S. McBride; research credit: S. McBride et al.; via Physics Today)
Lenticular Landscape
Mountain ridgelines push oncoming winds up and over their peaks, creating the conditions for some spectacular condensation. If the displaced air is moist enough, it cools and condenses into a cloud that appears to hover over the peak. In reality, winds are constantly moving up and over the mountain, condensing into visible cloud where the temperature is cool enough and then morphing back to water vapor once temperatures increase. This process can create stacked lenticular clouds like those seen here. This spot in New Zealand sees lenticular clouds so often that the formation has its own name: Taieri Pet! (Image credit: satellite image – L. Dauphin, b/w – National Library; via NASA Earth Observatory)
Black-and-white photo of an instance of the Taieri Pet lenticular cloud structure. 
Waves Break Up Floating Rafts
Small particles can float on a liquid, held together as a raft through capillary action. But those rafts — like the tea skin below — break up when waves jostle them. In this study, researchers looked at how standing waves broke up a raft of graphite powder. Although the raft’s break-up resembles fields of sea ice breaking apart, the researchers found that different mechanisms were responsible. In their experiment, waves pushed and pulled horizontally at the raft, causing it to fracture. But that push-and-pull is negligible in sea ice, where sheets instead break from the up-and-down motion of waves vertically bending the ice. Nevertheless, the new insights are valuable for various biofilms and some ice floes. (Image and research credit: L. Saddier et al.; via APS Physics)
The skin atop a cup of tea breaks up into polygons after stirring with a spoon. Although the effect resembles sea ice breakup, the specific wave mechanism differs. 
Feeding Hurricanes
With the strong hurricane season pummeling the southern U.S. this year, you may have heard comments about how warm oceans are intensifying hurricanes. Let’s take a look at how this works. Above is a map of ocean surface temperatures in late September, as Helene was developing and intensifying. For hurricanes, the critical ocean surface temperature is about 27 degrees Celsius — above this temperature, the warm waters add enough energy and moisture to the storm to intensify it. In this image, the waters colored from medium red to black are at or above this temperature. In fact Helene’s path — shown in a dotted white line — took it across particularly warm (and therefore dark) eddies with temperatures up to 31 degrees Celsius.
Many factors affect a hurricane’s formation and intensification; understanding and predicting storms, their path, and their strength remains an active area of research. But warmer ocean temperatures are better at sustaining the hurricane’s warm core, and their moisture is easier to evaporate, thereby fueling the storm. Unfortunately, as the climate warms, we have to expect that warmer oceans will help rapidly intensify tropical storms and hurricanes. (Image credit: W. Liang; via NASA Earth Observatory)
When Fires Make Rain
The intense heat from wildfires fuels updrafts, lifting smoke and vapor into the atmosphere. As the plume rises, water vapor cools and condenses around particles (including ash particles) to form cloud droplets. Eventually, that creates the billowing clouds we see atop the smoke. These pyrocumulus clouds, like this one over California’s Line fire in early September 2024, can develop further into full thunderstorms, known in this case as pyrocumulonimbus. The storm from this cloud included rain, strong winds, lightning, and hail. Unfortunately, storms like these can generate thousands of lightning strikes, feeding into the wildfire rather than countering it. (Image credit: L. Dauphin; via NASA Earth Observatory)
“Immersion”
Some seabirds, including gannets and boobies, feed by plunge diving. From high in the air, they fold their wings and dive like darts into the water, impacting at speeds around 24 m/s to help them reach the depths where their prey swim. With their narrow beaks and necks, the critical moments in this feat come when the bird’s head is submerged but its body remains out of the water. At this point, the bird’s head is decelerating quickly and its body is still moving at full speed; if the neck cannot withstand this combination of forces, it will buckle.
But plunge divers, it turns out, have a secret weapon that helps them handle impact: their head shape. A study of water entry dynamics using 3D-printed models of birds’ heads found that plunge divers have a shape that increases the amount of time it takes to enter the water. The impact forces stretch out over that longer period of contact, which also stretches out the time it takes for the bird to reach its maximum deceleration. The end result? That extended contact time protects birds from unsafe levels of deceleration, just like a crumple-zone in a crashing car keeps its occupants from experiencing the worst decelerations. (Image credit: K. Zhou/BPOTY; research credit: S. Sharker et al.; via Colossal)
Engineering Our Landfills
We create a lot of waste and, at least for now, much of that waste goes into landfills. Properly managing garbage requires much more than digging a hole in the ground, as Grady from Practical Engineering shows in this video. Maintaining a landfill requires careful management of water, soil, landfill strata, and even gas buildup. And these challenges don’t end once the trucks stop arriving. Landfills require decades of care even after their closure. Check out the video to learn more about how these artificial structures are built, managed, and maintained. (Video and image credit: Practical Engineering)
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