Roll Cloud Over Wisconsin
31.08.2011

What kind of cloud is this? A type of arcus cloud called a roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud.

Moons, Rings, Shadows, Clouds: Saturn (Cassini)
2.04.2018

While cruising around Saturn, be on the lookout for picturesque juxtapositions of moons, rings, and shadows. One quite picturesque arrangement occurred in 2005 and was captured by the then Saturn-orbiting Cassini spacecraft. In the featured image, moons Tethys and Mimas are visible on either side of Saturn's thin rings, which are seen nearly edge-on.

A Roll Cloud Over Uruguay
2.06.2013

What kind of cloud is this? A roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud.

Saturn's Cloud Tops
17.03.1996

This close-up of the tops of Saturn's clouds was taken by the Voyager 1 robot spacecraft as it passed the giant planet in November 1980. Saturn's clouds are mostly composed of hydrogen and helium gas, but the small addition of other elements gives the clouds their colors.

Mammatus Clouds Over Mexico
30.12.2007

Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud.

Colorful Water Clouds Over Mars
17.04.2001

One place where water can be found on Mars is in clouds. In the above picture colorful water clouds are visible just after sunrise in and around a maze of canyons known as Noctis Labyrinthus (the labyrinth of the night).

Clouds and Crescents
4.01.2014

A crescent Venus shines along the western horizon at dusk in this clearing sky. The Earth's sister planet is smiling between the low clouds near the bottom of the frame during its January 2nd conjunction with the slender, young crescent Moon above.

A Lenticular Cloud Over New Hampshire
30.04.2003

Why does this cloud look so strange? Actually, pictured above are several clouds all stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes.

Mammatus Clouds over Saskatchewan
11.08.2021

When do cloud bottoms appear like bubbles? Normally, cloud bottoms are flat. This is because moist warm air that rises and cools will condense into water droplets at a specific temperature, which usually corresponds to a very specific height. As water droplets grow, an opaque cloud forms.

APOD: 2024 July 9 Б Noctilucent Clouds over Florida
9.07.2024

These clouds are doubly unusual. First, they are rare noctilucent clouds, meaning that they are visible at night -- but only just before sunrise or just after sunset. Second, the source of these noctilucent clouds is actually known.