Sand Dunes Thawing on Mars
3.03.2008

What are these strange shapes on Mars? Defrosting sand dunes. As spring now dawns on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured above, are beginning to thaw. The carbon dioxide and water ice actually sublime in the thin atmosphere directly to gas.

A Lunar Corona over Turin
16.09.2019

What are those colorful rings around the Moon? A corona. Rings like this will sometimes appear when the Moon is seen through thin clouds. The effect is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud.

When Rainbows Smile
11.03.2022

Want to see a rainbow smile? Look near the zenith (straight up) when the sun is low in the sky and you might. This example of an ice halo known as a circumzenithal arc was captured above a palm tree top from Ragusa, Sicily on February 24.

APOD: 2024 May 30 Б A Lunar Corona over Paris
30.05.2024

Why does a cloudy moon sometimes appear colorful? The effect, called a lunar corona, is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently.

APOD: 2025 December 16 Б Andromeda and Sprites over Australia
16.12.2025

WhatБs happening over that tree? Two very different things. On the left is the Andromeda galaxy, an object that is older than humanity and will last billions of years into the future. Andromeda (M31) is similar in size and shape to our own Milky Way Galaxy.

Shadow at the Lunar South Pole
28.11.1995

In 1994, the space probe Clementine spent 70 days in lunar orbit mapping the Moon's surface. Shown above is a dramatically detailed composite view centered on the Moon's South Pole constructed from 1500 Clementine images.

Veins of Heaven
31.07.2014

Transfusing sunlight through a a still dark sky, this exceptional display of noctilucent clouds was captured earlier this month above the island of Gotland, Sweden. From the edge of space, about 80 kilometers above...

Milky Way over Yellowstone
29.01.2020

The Milky Way was not created by an evaporating lake. The pool of vivid blue water, about 10 meters across, is known as Silex Spring and is located in Yellowstone National Park in Wyoming, USA. Steam rises off the spring, heated by a magma chamber deep underneath known as the Yellowstone hotspot.

Lunar Dust and Duct Tape
29.05.2021

Why is the Moon so dusty? On Earth, rocks are weathered by wind and water, creating soil and sand. On the Moon, the history of constant micrometeorite bombardment has blasted away at the rocky surface creating a layer of powdery lunar soil or regolith.

Galaxy by the Lake
10.09.2022

This 180 degree panoramic night skyscape captures our Milky Way Galaxy as it arcs above the horizon on a winter's night in August. Near midnight, the galactic center is close to the zenith with the clear waters of Lake Traful, Neuquen, Argentina, South America, planet Earth below.