The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Glacier?
  Ice can be a powerful force of erosion, particularly when it accumulates into thick deposits.
• Mantling Material on Crater Floor
  This image shows remnants of a mantling deposit on the floor of a crater in the Southern highlands of Mars.
• Scarp and Channels in a Crater in Terra Cimmeria
  This image shows a crater in Terra Cimmeria, approximately 10 km in diameter. The roughly concentric ridges and troughs in this crater's floor are known as "concentric crater fill."
• Gullies in Trough near Gorgonum Chaos
  This image shows gullies in a trough that is near Gorgonum Chaos, a region filled with gullies.
• Alluvial Fan along a Crater Wall
  This observation covers an alluvial fan along the wall of a large crater in the mid latitudes of the Southern hemisphere of Mars.
• Valleys on the Ejecta Blanket from Cerulli Crater
  This HiRISE image reveals valleys that cross the ejecta from the large impact crater Cerulli to the south.

The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Lava Flows at the Base of Olympus Mons
  Olympus Mons is the largest volcano in the Solar System and is thought to be quite young (compared to other features on Mars). So, what happens to all those lava flows running off of Olympus Mons?
• Lava Channel on the Flank of Ascraeus Mons
  Ascraeus Mons is one of the giant shield volcanoes on Mars. Its flanks are built up of innumerable lava flows, but most are buried by too much dust to see features of interest.
• Gullies and Seasonal Frost in a Crater
  This scene shows the curving, Eastern interior walls of a 12 kilometer-diameter impact crater in the Southern mid-latitudes of Mars.
• Alluvial Fan in Far Western Terra Tyrrhena
  This image shows portions of an alluvial fan complex in Harris Crater, an approximately 83-kilometer diameter crater located on the Northern rim of the Hellas Basin.
• Dunes in Mars' Polar Erg
  Near the North pole of Mars, the landscape is dominated by sand dunes forming a massive erg (sand sea), much like parts of the Sahara Desert on Earth.
• Cones Formed by Hot Lava Running over Water or Ice
  These cones are similar in size and shape to cones found in Iceland where hot lava has run over wet ground.

The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• DTM: Area Traversed by Mars Exploration Rover
  This digital terrain model covers the area that has been explored by Opportunity on Meridiani Planum.
• Concentric Crater Fill in the Northern Plains
  This observation shows part of an unnamed crater located in the Northern plains.
• Dry Ice and Dunes
  Mars has a vast sea of sand dunes in the high latitude region encircling its North polar cap, known as the North polar erg.
• Gullies in a Crater Wall
  This image displays several nice examples of classical "alcove-channel-apron" gullies in a 10 kilometer (about 6 miles) diameter crater located in Mars' Northern mid-latitudes.
• DTM: North Polar Crater
  Impact craters on the North polar cap, such as the one in this digital terrain model, are rare which tells us that the landscape is being actively resurfaced.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Bull's-Eye Impact Crater
  What caused the central pit within this impact crater: unusual subsurface layering or a lucky second impact?
• Layered Rocks in a Crater in Arabia Terra
  This image shows a ground surface composed of many thin light– and dark–toned layers.
• Dark Dunes in Herschel Crater
  This observation shows part of the floor of Herschel Crater, a roughly 300 kilometer wide impact basin located in the southern cratered highlands of Mars.
• Layered Deposits in Aureum Chaos
  This observation shows an outcrop of a large slab of layered deposits in Aureum Chaos.
• Dust Fans on the Seasonal Carbon Dioxide Polar Cap
  During the long dark night of Martian winter at the South Pole, carbon dioxide in its solid form accumulates and forms a seasonal polar cap.
• Popular Landform in Cydonia Region
  HiRISE captured this image (in 2007) of an eroded mesa made famous by its similarity to a human face in a Viking Orbiter image with much lower spatial resolution and a different lighting geometry.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Boulder Tracks on the Slopes of Noctis Labyrinthus
  This image spans the floor and two walls of a pit in Noctis Labyrinthus, a system of deep, steep-walled valleys on the western edge of Valles Marineris.
• Future Mars Landing Site in Acidalia Mensa
  Candidate landing site in Acidalia Mensa for future Mars missions.
• Spokes, Creep, and Channels in a Crater in Utopia Planitia
  This observation shows an unnamed impact crater located in Utopia Planitia; this crater is more than 10 kilometers (6.25 miles) in diameter and 700 meters (765 yards) deep.
• Slipping and Sliding in Coprates Chasma
  This observation shows a landslide in the Coprates Chasma region of Valles Marineris that occurred when a large unstable area of rock broke away from the cliffs along the top of the image.
• Layered Mesa in Coprates Chasma
  This observation shows a mesa within Coprates Chasma, a large trough in the Valles Marineris canyon system.
• Mantles and Flows in Moreux Crater
  This HiRISE image shows part of the central uplift of Moreux Crater, at about 42° North of the equator.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Future Mars Landing Site in Antoniadi Crater
  Candidate landing site in Antoniadi Crater for future Mars missions.
• White Rock Landform in Pollack Crater
  This image shows a portion of a relatively bright landform named "White Rock" on the floor of Pollack crater in the Sinus Sabaeus region of Mars.
• Meanders in Nanedi Valles
  This observation shows a portion of Nanedi Valles, an equatorial Martian valley network.
• Dissected Mantled Terrain
  A northern mid-latitude scene consisting of craters, intercrater plains, and mantled material is visible in this HiRISE image.
• Glacier-Like Flow on Arsia Mons Flank
  This observation shows glacier-like flow in a depression in the flanks of Arsia Mons.
• Interior Layered Deposits in Juventae Chasma
  This observation shows a portion of interior layered deposits (ILD) in Juventae Chasma.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Bouldery Deposit on Crater Floor
  This image shows a degraded impact crater in the southern highlands.
• (Almost) Silent Rolling Stones in Kasei Valles
  This observation shows the very steep side of a plateau, part of the northern limit of the Kasei Valles system, which is one of the largest outflow channel systems on Mars.
• Light Outcrop on Crater Floor
  This observation shows part of the floor of a large impact crater in the southern highlands, north of the giant Hellas impact basin.
• Gullies on Gorgonum Chaos Mesas
  This observation shows part of Gorgonum Chaos, a large cluster of chaotic terrain found in the southern hemisphere.
• Sand Dune Field in Richardson Crater
  This observation is a view of the sand dune field in Richardson Crater covered with seasonal frost.
• South Polar Layered Deposits and Residual Cap
  This image shows a variety of surface textures within the south polar residual cap of Mars.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Sand Dunes near the North Pole
  This HiRISE image shows some large sand dunes near the North Pole of Mars.
• Strange Squishy Impact Crater
  This crater is one of a small group of highly unusual craters found in the Northern lowlands near the Elysium Mons volcano.
• Butterfly Ejecta around a Fresh
  The approximately 650 meter (2135 foot) diameter crater in this image is relatively fresh, as evidenced by its sharp rim and unmodified shape.

The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Diverse Lava Flows on Olympus Mons
  The flanks of Olympus Mons are covered with lava flow after lava flow.
• Clay Diversity on Flank of Mawrth Vallis
  This observation is a candidate landing site for the Mars Science Laboratory (MSL) rover -- named Curiosity -- to be launched in 2011.
• Gullies and Arcuate Ridges
  This observation shows gullies and arcuate ridges in a crater in the southern hemisphere of Mars.
• Scalloped Depressions with Layers in the Northern Plains
  This image, of the northern plains of Mars, is marked by depressions in a layer of material that covers the region.
• Light-Toned Material in Melas Chasma
  This observation shows an outcrop of bright material in Melas Chasma, part of the giant Valles Marineris trough system.
• Monitoring South Polar Cap Swiss-Cheese Terrain Change
  This image is taken in one of the troughs that are typical within the stack of Martian south polar layered deposits.
• Aram Chaos Sediments
  Aram Chaos appears to be a former impact crater.

The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Impact Crater Cut by Faults
  This image reveals an interesting coincidence of two important planetary processes: impact cratering and tectonism.
• Dunes and Polygons in Olympia Undae
  This observation shows dark dunes and light polygonal terrain in Olympia Undae, also known as the North Polar Erg.
• Aeolian Ripples within Slope Streak Beds
  Slope streaks, commonly seen in dust-rich equatorial regions of Mars, have been observed in all spacecraft images from the early Mariner missions to the most recent Mars Reconnaissance Orbiter mission.
• Dusty Lava Flows on Ascreaus Mons
  Ascreaus Mons is one of the giant shield volcanoes in the Tharsis region of Mars.
• Southern Layered Mound and Floor in Gale Crater
  This observation shows the interior of Gale Crater, a region being considered as a landing site for the 2011 Mars Science Laboratory.
• Joint Observation of the Isidis Basin with the Rosetta Mission
  This image of the floor of the Isidis Basin was taken in coordination with the Mars flyby of the European Rosetta mission.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Impact Crater Teetering on the Edge of a Canyon
  This observation shows the intersection of several geologic features at the edge of the huge Valles Marineris system of canyons on Mars.
• Ancient Terrain Near Tyrrhena Patera
  This observation covers a small part of the plains surrounding the volcano Tyrrhena Patera.
• Southern Hemisphere Craters
  This observation shows two southern hemisphere craters.
• Dusty Volcanic Vent in Syria Planum
  Previous images of this area by other space missions indicate that this is a shield volcano with very shallow slopes.
• Sample Tharsis Tholus Caldera Wall
  This image captures one of the cleaner portions of the interior wall of the caldera at the top of Tharsis Tholus.
• Ancient Lava Plain in Thaumasia Planum
  This observation samples part of an ancient lava plain in Thaumasia Planum.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Exposures of Different Rocks in Eos Chasma
  The bright rock exposures in this image occur along the walls of a 60-kilometer diameter impact crater.
• Northern Hemisphere Gullies on West-Facing Crater Slope
  This image shows the eastern (west-facing) side of an impact crater in the mid-latitudes of the Northern hemisphere.
• Flow Features in Amazonis Planitia
  Located between the Tharsis and Elysium volcanic provinces, Amazonis Planitia's relatively smooth surface and sparseness of sizeable craters has made it a good example for the most recent period in Mars geological history.
• Exposed Light Material in Upland Region in Aureum Chaos
  The plateau visible in this image is located within Aureum Chaos.
• Low Albedo Feature in Aeolis and Zephyria Regions
  This image is taken of an interesting linear feature in the Aeolis and Zephyria regions.

The following new captioned and spotlight images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Polygonal Ridges
  This image from the Gordii Dorsum region of Mars shows a large area covered with polygonal ridges in an almost geometric pattern.
• Gully Landforms in Aram Chaos
  This observation shows erosional features on light-toned rocks in Aram Chaos, a crater near the equator of Mars that has been nearly filled with sedimentary rocks.
• Pit Craters of Tractus Catena
  These pits formed through collapse above an underground void.
• Eroding Crater Fill
  This image shows the edge of a mound of sediments in the center of a large impact crater near Amenthes Planum.

Scientists have reconstructed the formation of two curious features in the northern ice cap of Mars -- a chasm larger than the Grand Canyon and a series of spiral troughs -- solving a pair of mysteries dating back four decades while finding new evidence of climate change on Mars.

In a pair of papers to be published in the journal Nature on May 27, Jack Holt and Isaac Smith of The University of Texas at Austin's Institute for Geophysics and their colleagues describe how they used radar data collected by NASA's Mars Reconnaissance Orbiter to reveal the subsurface geology of the red planet's northern ice cap.

The following new captioned images taken by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter spacecraft are now available:

• Geezer Gullies at Tempe Terra
  This image shows gullies in the walls of a large impact crater in Tempe Terra.
• Viscous Flow in Protonilus Mensae
  This subimage highlights a feature that resembles a terrestrial glacier, indicating that material has viscously flowed at this location.
• Star Dunes in Crater in Tyrrhena Terra
  An amazing aspect of Mars that is captured in many HiRISE images is geologic diversity within a small area.
• Icy Northern Dunes
  Like Earth, Mars has seasonal polar caps that grow in the winter and retreat in the spring, but on Mars the seasonal caps are composed primarily of carbon dioxide (dry ice).
• Pits along Fractures in Crater Floor Material
  This image shows the degraded rim of a large impact crater which is partly filled with material that is fractured in several places, especially near the crater rim.
• Collapse!
  This observation shows part of an unnamed crater whose fill material has collapsed.
• Intra-Crater Structure in NW Hellas Basin
  This area of Hellas Basin has a number of unusual features which are thought to be quite old because of the high crater density.
• Big Impact-Triggered Dust Avalanche
  MRO's Context camera (CTX) acquired the image at lower left on18 Nov 2007 and the adjacent image on 14 Feb 2010, showing a large new slope streak in the aureole (giant landslide deposits) of Olympus Mons.
• Megabreccia in the Central Uplift of Stokes Crater
  Stokes is a large, approximately 60 kilometer diameter (38 miles) impact crater located in the Northern lowland plains of Mars.
• Deformed Craters and Polygons in Utopia Planitia
  This image of Utopia Planitia shows some deformed craters. The crater rims are not round but elliptical and even angular.
• Knobs near Reull Vallis
  This observation shows a knob and large crater near Reull Vallis, east of the Hellas Basin.
• Light-Toned Rocks inside a Crater
  This approximately 20 kilometer diameter impact crater is located just to the south of Coprates Chasma in Valles Marineris.