In many geophysical and metallurgical processes, there is a stage with a porous layer of liquid-infused solid known as a mushy layer. Such layers form in sea ice, in cooling metals, and even in the depths of our mantle. Within the mushy layer, temperature, density, and concentration can vary dramatically from one location to another.
The image above shows a mushy layer made from a mixture of water and ammonium chloride. Above the mushy layer, green plumes drift upward, carrying lighter fluid. Look closely within the mushy layer and you’ll see narrow channels feeding up to the surface. These are known as chimneys. In sea ice, chimneys like these carry salty brine out of the ice and into the seawater, increasing its salinity. See this Physics Today article for more details on the dynamics of mushy layers. (Image credit: J. Kyselica; via Physics Today)
I’m not normally one to talk about myself here on FYFD. This site was made to keep the focus on the science, but I’m making an exception today to share a very special exhibit that I’m a part of: the #IfThenSheCan Exhibit, which opens today at the Smithsonian in Washington, DC as part of their #WomensFuturesFestival.
The exhibit features over 120 statues of real women in STEM careers — everything from robotics to marine biology, artificial intelligence to aerospace engineering. It is an absolutely amazing bunch of women, and I am so honored to be a part of it.
My statue, while on display in Dallas. Photo by Regina Binz.
If you’re in the DC area before March 27th, be sure to swing by the National Mall and see the statues. (If not, you can take a virtual tour, too!) Currently, they are all located at the Arts + Industries Building, the Smithsonian Castle and the adjacent Enid A. Haupt Garden, but after March 7th, some of the statues will move to other museums around the Mall. Mine is heading to the National Air and Space Museum!
When I was twelve years old, I visited DC for the first time, and everything about that trip made a huge impression on me. I was in awe of the history, the memorials, the public transit, and, most of all, the National Air and Space Museum. My parents complained that every time we walked the Mall, I made a beeline — as if drawn by a magnetic field — right up the steps of that building. To be a part of that museum now, some twenty years later, is something I never could have imagined.
I’m so proud to be part of this initiative full of amazing women inspiring the next generation of STEM innovators! Special thanks to AAAS and Lyda Hill Philanthropies for making it all possible. (Image credits given in each description/caption.)
Water is an odd substance because it is densest at 4 degrees Celsius, well above its melting point at 0 degrees Celsius. This density anomaly means that melting ice takes on very different shapes, depending on the temperature of the water surrounding it. At low temperatures (under 4 degrees Celsius), the cold water melting off the ice is denser than the surroundings, so it sinks. The sinking fluid melts lower portions of the ice faster, leading to an inverted pinnacle (Image 1).
In contrast, at higher temperatures (above 7 degrees Celsius), the meltwater is lighter than the surroundings and therefore rises, creating an upward-pointing pinnacle (Image 3). At intermediate temperatures, some areas of the ice see rising meltwater and some see sinking. This complicated flow pattern sets up vortices that result in a scalloped edge along the ice (Image 2). (Image and research credit: S. Weady et al.; via APS Physics)
Line-like clouds criss-cross the Pacific Ocean in this satellite image. Each one is a ship track, a remnant left behind a passing ship. As they travel, ships leave a trail of exhaust that seeds the atmosphere with aerosols that serve as additional nucleation sites for clouds. The tiny particles interact with existing low-level clouds, making them brighter. Of course, the aerosols are present in the wake of ships regardless of whether they seed clouds that we can observe. (Image credit: J. Stevens; via NASA Earth Observatory)
Lava flows are, by definition, transient. In his LAVA series, photographer Jan Erik Waider explores the changing vistas and textures of Iceland’s Fagradalsfjall volcano eruption. Using a telephoto lens, he captures incredible details of the charred, cooling outer crust of the lava and the glowing molten interior. Only minutes later, fresh lava tore through, destroying these natural sculptures. You can find prints of his images on his website. (Image credit: J. Waider; via Colossal)
This astronaut photo shows the Isles of Scilly off the Cornish coast. The pale turquoise waters mark shallow reefs and shoals between the islands while blues reveal deeper waters surrounding the isles. The sun angle is perfect for highlighting the complex wave patterns caused by the winds and tides. Look closely and you’ll see swells intersecting one another and even diffracting around the smaller islets. (Image credit: NASA; via NASA Earth Observatory)
Soap bubbles are delicate and ephemeral, always a breath away from collapse due to thinning driven by gravity or evaporation. But that frailty can be countered. Adding microparticles to the bubble’s shell in place of surfactants counters drainage and makes bubbles last for tens of minutes (left). Adding glycerol to the mix takes things a step further (right). The glycerol, which absorbs water from the surrounding air, counteracts the evaporation, allowing bubbles to remain intact — with no discernible change to their radius — almost indefinitely. So far the researchers have made such a bubble last for 465 days! (Image and research credit: A. Roux et al.; via APS Physics)
As summer approaches in the Southern Ocean, sea ice melts, but the process is not purely one-way. Temperatures in some locations are cold enough for some limited new freezing. The result is a mix of ice conditions like those seen here. The oldest, thickest ice is part of the ice shelf in the image’s lower right. Normally, younger sea ice would nestle against this shelf, but strong winds have blown that ice north-eastward.
In the open waters between, delicate frazil ice — tiny needle-like crystals — forms. The wind, coupled with the wave motion, drives the frazil ice together to form streaks of nilas, which eventually accumulate into a layer along the older, broken, windswept ice. (Image credit: J. Stevens/USGS; via NASA Earth Observatory)
Lean in to a glass of champagne and you’ll hear a soft chorus of sound as the bubbles pop. Recently, researchers determined the specific mechanism in the process that’s responsible for that audible sound.
Bubbles pop when the thin film of liquid separating them from the atmosphere drains away. The moment the film opens corresponds to the start of the sound, as overpressurized air inside the bubble has a chance to escape. The researchers found that the bubble behaves like a open-ended Helmholtz resonator, and by the time the sound emission ends, the bubble’s collapse has barely begun. (Image credit: L. Lyshøj; research credit: M. Poujol et al.)
As scientists continue to unravel the peculiarities of ice, they’ve found that ice’s friction depends both on the object sliding on it and the ice’s hardness. At extremely low temperatures, water molecules at the ice’s surface are held rigidly by the hard ice, resulting in high friction. At intermediate temperatures, however, water molecules at the surface were more mobile — especially with a quick-moving slider going by — so the friction decreased.
But as the ice approached its melting point, the friction behavior shifted again. As the ice softened, sliding objects could begin to plough into the ice, dramatically increasing contact and friction. When ploughing begins depends on temperature, slider shape, contact pressure, slider speed, and ice hardness.
Beyond the lab, researchers found that weather plays a role in slideability, too, since humidity and air temperature can affect the thickness of the liquid-layer at the ice’s surface. (Image credit: SHVETS Productions; research credit: R. Liefferink et al.; via APS Physics; submitted by Kam-Yung Soh)
