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This Hubble image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. As the two galaxies smash together, billions of stars are born, mostly in groups and clusters of stars. The brightest and most compact of these are called super star clusters.
Credit: Credit: NASA, ESA, and the Hubble Heritage Team STScI/AURA)-ESA/Hubble Collaboration.

Acknowledgement: B. Whitmore ( Space Telescope Science Institute) and James Long (ESA/Hubble).

In the winter a layer of carbon dioxide ice (dry ice) covers the north polar sand dunes. In the spring the sublimation of the ice (going directly from ice to gas) causes a host of uniquely Martian phenomena.

In this subimage streaks of dark basaltic sand have been carried from below the ice layer to form fan-shaped deposits on top of the seasonal ice. The similarity in the directions of the fans suggests that they formed at the same time, when the wind direction and speed was the same. They often form along the boundary between the dune and the surface below the dunes.

Written by: Candy Hansen

Dunes are often found on crater floors. In the winter time at high northern latitudes the terrain is covered by carbon dioxide ice (dry ice). In the spring as this seasonal ice evaporates many unusual features unique to Mars are visible.

On the floor of this crater where there are no dunes, the ice forms an uninterrupted layer. On the dunes however, dark streaks form as surface material from below the ice is mobilized and deposited on top of the ice. In some cases this mobile material probably slides down the steep face of the dune, while in other cases it may be literally blown out in a process of gas release similar to removing a cork from a champagne bottle.

Written by: Candy Hansen

This composite image is a view of the colorful Helix Nebula taken with the Advanced Camera for Surveys aboard NASA/ESA Hubble Space Telescope and the Mosaic II Camera on the 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile. The object is so large that both telescopes were needed to capture a complete view.

The Helix is a planetary nebula, the glowing gaseous envelope expelled by a dying, sun-like star. The Helix resembles a simple doughnut as seen from Earth. But looks can be deceiving. New evidence suggests that the Helix consists of two gaseous disks nearly perpendicular to each other.

Credit: NASA, ESA, C.R. O'Dell (Vanderbilt University), and M. Meixner, P. McCullough, and G. Bacon ( Space Telescope Science Institute)

This image from the Gordii Dorsum region of Mars shows a large area covered with polygonal ridges in an almost geometric pattern.

The ridges may have originally been dunes which hardened (indurated) through the action of an unknown process. Groundwater might have been involved.

Written by: Nicolas Thomas

This enhanced-color image shows a surface with diverse colors just southwest of Nili Fossae. The color diversity of this mesa suggests that the surface has a varied composition, perhaps recording chemical processes of ancient Mars.

Much of the surface shows a chaotic mix of colors, but the northern impact crater exposes distinct layers. Different layers have different colors. There are several possible reasons for this: the events that formed the layers could have drawn material from different sources, or the layers could have been altered differently after they formed, for reasons such as varying porosity.

Written by: Colin Dundas

Mawrth Vallis has a rich mineral diversity, including clay minerals that formed by the chemical alteration of rocks or loose regolith" (soil) by water. There is a high surface area of bedded phyllosilicate (clay) exposures (tens of kilometers), located in the bright-toned materials.

The CRISM instrument on the MRO spacecraft detects a variety of clay minerals here, which could signify different processes of formation. The high resolution of the HiRISE camera helps us to see and trace out layers, polygonal fractures, and with CRISM, examine the distribution of various minerals across the surface.

This surface is scientifically compelling for the Mars Science Laboratory (MSL) rover Curiosity and this region is one of four candidate landing sites for MSL.

Written by: Jennifer Griffes