Monday, 15 December 2025
Frosted Dunes
These polar dunes on Mars show both carbon dioxide frost (the white colored areas) along with darker material that’s been exposed due to sublimation, and is blown by the wind to form these dark spots. The largest dunes can reach several hundred meters in width. Taken by the HiRISE camera onboard NASA's Mars Reconnaissance Orbiter in 2018 from 302 km above the surface. The imaged area is less than 1 km across.
Tuesday, 16 December 2025
Aurora and Moonbow from Skógafoss
Night on Earth can feel uncanny, as though the colors have quietly slipped away. The familiar world flattens into shades of gray. And yet, on a few rare nights each year, color returns—suddenly and spectacularly.
When the Sun, Moon, and Earth align just right, moonlight meets the mist at the base of a great waterfall. The result is a moonbow: a rainbow born not of daylight, but of reflected lunar light.
That light begins its journey at the Sun, traveling ninety-three million miles through space before glancing off the Moon’s surface. From there, it slips into Earth’s atmosphere, scatters through countless water droplets in the falling spray, and finally enters an eye. A signal travels to the brain, and the mind reconstructs the scene as something beautiful.
The aurora borealis follows a similar logic, though its source is far more violent. Charged particles from geomagnetic storms race toward Earth, guided by magnetic fields into the upper atmosphere, where they excite atoms into glowing pillars of light. Again, the brain assembles invisible processes into visible wonder.
Moonbows and auroras are not only beautiful; they are physics.
Color carries information. It tells us about structure, about energy, about processes unfolding over time. Because light travels freely across the universe, it becomes our messenger. By studying it, we can explore distant worlds without ever leaving Earth—and learn their stories, written in color, across the dark.
Wednesday, 17 December 2025
Jupiter's Marbled Clouds
This image from NASA's Juno spacecraft captures dramatic atmospheric features in Jupiter's northern hemisphere during its 18th close flyby of the gas giant. The swirling clouds surround a circular feature within the "Jet N6" region of the jet stream. Jupiter's atmosphere lacks a solid surface, allowing storms and wind patterns, or jet streams, to persist for centuries. The colors in the atmosphere come from the composition of different cloud layers made of elements like ammonia, water ice, sulfur, and phosphorus gases.
Thursday, 18 December 2025
Sprites Over Château de Beynac
A flash of lightning, and then—something else. High above a storm, a crimson figure blinks in and out of existence. If you see it, you are a lucky witness of a sprite, one of the least-understood electrical phenomena in Earth’s upper atmosphere.
Sprites occur at some 50 miles (80 kilometers) altitude, high above thunderstorms. They appear moments after a lightning strike – a sudden reddish flash that can take a range of shapes, often combining diffuse plumes and bright, spiny tendrils. Some sprites tend to dance over the storms, turning on and off one after another. Many questions about how and why they form remain unanswered. Sprites are the most frequently observed type of Transient Luminous Events (TLEs); TLEs can take a variety of fanciful shapes with equally fanciful names.
Friday, 19 December 2025
A Rare Gourd
NASA’s Hubble Space Telescope captured an uncommon sight – the death of a low-mass star – in this image of the Calabash Nebula released on Feb. 3, 2017.
Here, we can see the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed — the gas shown in yellow is moving close to a million kilometers an hour.
Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye – in astronomical terms. Over the next thousand years, the nebula is expected to evolve into a fully-fledged planetary nebula.
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