North Pole Below
20.10.2000

Orbiting over the north pole of planet Earth on May 5, the MODIS instrument on-board the Terra spacecraft, recorded this view of the ice cap 700 kilometers below. A radial grid centered on the pole is shown on top of the approximately true color image where each pixel covers about one square kilometer.

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.

Neutron Mars
15.03.2002

Looking for water on Mars, researchers using detectors on board the orbiting Mars Odyssey spacecraft have created this false-color global map of energetic neutrons from the otherwise Red Planet. What do neutrons have to do with water?

Unusual Plates on Mars
28.02.2005

What are those unusual plates on Mars? A leading current interpretation holds that they are blocks of ice floating on a recently frozen sea covered by dust. The unusual plates were photographed recently by the European Space Agency's Mars Express spacecraft currently orbiting Mars.

Night Lightning on Jupiter
16.12.1997

Why is there lightning on Jupiter? Lightning is a sudden rush of electrically charged particles from one location to another. To create lightning, charges must first separate inside a cloud. On Earth, drafts of colliding ice and water droplets usually create this charge separation, but what happens on Jupiter?

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.

Europa's Surface
13.08.1996

Voyager spacecraft images of Europa's surface, like the one above, are suggestive of sea ice on Earth. The criss-crossing dark streaks may indeed be cracks in its ice-covered surface caused by Jupiter's tidal stresses accompanied by the freezing and expansion of an underlying layer of water.

Young Martian Terrain
1.08.2001

What caused the pits, ridges, and gullies on otherwise smooth Martian terrain? One hypothesis is water. The lack of craters at this mid-latitude location indicates that the terrain is quite young by geological standards, perhaps only 100,000 years old.

La Nina Earth
15.02.1999

La Niña is a temporary climate change caused by unusually cold water in the central Pacific Ocean. Cold water topping an unusually low sea level is shown as purple in the above false-color picture taken by the orbiting TOPEX/Poseidon satellite in mid-January.

Old Faithful Meets Hale-Bopp
26.05.1997

As Comet Hale-Bopp leaves our Northern Skies, it provides us with yet another burst of joy. On May 11th the fading comet was photographed behind the famous "Old Faithful" water geyser of Yellowstone National Park, Wyoming, USA, Planet Earth.