A Proton Aurora
17.12.2003

What are auroras made out of? Most auroras are caused by the solar wind exciting electrons that are funneled down the Earth's magnetic field. These electrons strike air molecules, liberating other electrons that glow when re-acquired.

Titan, Rings, and Saturn from Cassini
8.03.2011

How thin are the rings of Saturn? Saturn's rings to be about one kilometer thick, making them many times thinner, in relative proportion, than a razor blade. This thinness sometimes appears in dramatic fashion during an image taken nearly along the ring plane.

Dark Sand Cascades on Mars
25.11.2012

They might look like trees on Mars, but they're not. Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost. The above image was taken in 2008 April near the North Pole of Mars.

Dark Sand Cascades on Mars
29.11.2015

They might look like trees on Mars, but they're not. Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost. The above image was taken in 2008 April near the North Pole of Mars.

APOD: 2025 November 2 Б A Horseshoe Einstein Ring from Hubble
2.11.2025

What's large and blue and can wrap itself around an entire galaxy? A gravitational lens mirage. Pictured here, the gravity of a massive elliptical galaxy (luminous red galaxy: LRG) has gravitationally distorted the light from a much more distant blue galaxy.

Jupiter, Io, and Shadow
7.12.2002

Pictured above is the innermost of Jupiter's Galilean satellites, Io, superposed in front of the gas giant planet. To the left of Io is a dark spot that is Io's own shadow. A solar eclipse would be seen from within the shadow spot on Jupiter.

The Face on Mars
22.07.1995

This image, showing what looks to be a human face sculpted on the martian surface, was produced using data from NASA's Viking 1 orbiter in 1976. Described in a press release...

The Einstein Cross Gravitational Lens
27.03.2005

Most galaxies have a single nucleus -- does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar.

A Picturesque Venus Transit
23.06.2004

The rare transit of Venus across the face of the Sun earlier this month was one of the better-photographed events in sky history. Both scientific and artistic images have been flooding in from the areas that could see the transit: Europe and much of Asia, Africa, and North America.

Dark Sand Cascades on Mars
19.01.2010

They might look like trees on Mars, but they're not. Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost. The above image was taken in 2008 April near the North Pole of Mars.