Radiation Exposure Comparisons for a Trip to Mars

Measurements with the MSL Radiation Assessment Detector (RAD) on NASA's Curiosity Mars rover during the flight to Mars and now on the surface of Mars enable an estimate of the radiation astronauts would be exposed to on an expedition to Mars. NASA reference missions reckon with durations of 180 days for the trip to Mars, a 500-day stay on Mars, and another 180-day trip back to Earth. RAD measurements inside shielding provided by the spacecraft show that such a mission would result in a radiation exposure of about 1 sievert, with roughly equal contributions from the three stages of the expedition. A Sievert is a measurement unit of radiation exposure to biological tissue. This graphic shows the estimated amounts for humans on a Mars mission and amounts for some other activities.

Image credit: NASA/JPL-Caltech/SwRI

Note: For more information, see PIA17600: Radiation Measurements on Mars.

Possible Recent Erosion in Gale Crater

Images of locations in Gale Crater taken from orbit around Mars reveal evidence of erosion in recent geological times and development of small scarps, or vertical surfaces. These two images come from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.

The image on the left shows the Yellowknife Bay area examined by NASA's Curiosity Mars rover during the rover's first 11 months on Mars. The red arrow points to the contact between the Sheepbed and Gillespie geological members. The blue arrow points to the contact between the Gillespie Lake member and overlying Glenelg member, which also forms a small scarp. These two geological contacts form scarps due to variations in rock hardness as eroded by the wind. The effect is to generate rock exposures that are relatively youthful in a geological timescale, on the order of 70 million years.

The image on the right shows the KMS_9 area, which Curiosity may investigate on the rover's route to Mount Sharp. The purple arrow points to the contact between the lowermost striated unit and the middle bedded unit. The yellow arrow marks the contact between the middle bedded unit and the upper smooth hummocky material. It is possible that the rocks adjacent to these scarps have also been only recently exhumed and exposed due to wind erosion.

The left image is a portion of HiRISE observation ESP_028335_1755, taken on August 12, 2012. Other image products from this observation are available at http://www.uahirise.org/ESP_028335_1755. The right image was taken on August 9, 2010, and other products from the same observation are available at http://www.uahirise.org/ESP_018920_175.

Image credit: NASA/JPL-Caltech/MSSS

Juventae Chasma Topography

Color-coded topography map of Juventae Chasma. White and red show the highest terrains, while blue and purple show the deepest.

The floor of Juventae Chasma sits some 5.8 km below the surrounding plateau. It is filled with sand in the southern part (left), which takes on a smooth appearance, in contrast to the northern (right) part of this image where many blocky rock fragments have slumped down from the chasma walls. Two large mounds of layered material sit inside Juventae Chasma and comprise minerals altered by water.

This region was imaged by the high-resolution stereo camera on ESA’s Mars Express on 4 November 2013 (orbit 12,508), with a ground resolution of 16 ms per pixel. The image center is at about 4°S / 298°E.

Image credit: ESA/DLR/FU Berlin (G. Neukum)

Note: For more information, see Juventae Chasma 3D.

Tithonium Chasma

The steep northern wall of Tithonium Chasma crosses this VIS image. Landslide deposits from slope failure can be seen at the lower left corner of the image.

Orbit Number: 52610 Latitude: -4.11268 Longitude: 274.623 Instrument: VIS Captured: 2013-10-23 18:45

Photo credit: NASA/JPL-Caltech/Arizona State University

Juventae Chasma Perspective

The largest layered mound in Juventae Chasma is seen here in close-up perspective view. It is about 53 km long, up to 20 km wide and rises some 3.3 km above the surrounding area, comparable to a small mountain range on Earth.

Its surface is etched with grooves carved by strong prevailing winds blowing through the chasma. Layers in the mound consist of sulphate-rich materials, an indication that the rocks have been altered by water.

The mound is a relic of at least 3 billion years of martian history and its layers were most likely built up as lake deposits over time. But ice-laden dust raining out from the atmosphere – a phenomenon observed at the poles of Mars – may also have contributed to the formation of the layers.

This region was imaged by the high-resolution stereo camera on ESA’s Mars Express on 4 November 2013 (orbit 12,508), with a ground resolution of 16 m per pixel. The image center is at about 4°S / 298°E.

Image credit: ESA/DLR/FU Berlin (G. Neukum)

Channels in Elysium Planitia

The channels in this VIS image are located in Elysium Planitia and were likely created by lava flow.

Orbit Number: 52601 Latitude: 12.7686 Longitude: 147.552 Instrument: VIS Captured: 2013-10-23 02:51

Photo credit: NASA/JPL-Caltech/Arizona State University

Juventae Chasma

Intriguing mounds of light-toned layered deposits sit inside Juventae Chasma, surrounded by a bed of soft sand and dust.

The origin of the chasma is linked to faulting associated with volcanic activity more than 3 billion years ago, causing the chasma walls to collapse and slump inwards, as seen in the blocky terrain in the right-hand side of this image.

At the same time, fracturing and faulting allowed subsurface water to spill out and pool in the newly formed chasm. Observations by ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter show that the large mounds inside the chasma consist of sulphate-rich materials, an indication that the rocks were indeed altered by water.

The mounds contain numerous layers that were most likely built up as lake-deposits during the Chasma’s wet epoch. But ice-laden dust raining out from the atmosphere – a phenomenon observed at the poles of Mars – may also have contributed to the formation of the layers.

While the water has long gone, wind erosion prevails, etching grooves into the exposed surfaces of the mounds and whipping up the surrounding dust into ripples.

The image was taken by the high-resolution stereo camera on ESA’s Mars Express on 4 November 2013 (orbit 12 508), with a ground resolution of 16 m per pixel. The image center is at about 4°S / 298°E.

Image credit: ESA/DLR/FU Berlin (G. Neukum)

Note: For more information, see Juventae Chasma Context.

Arcuate Fractures in Elysium Planitia

The arcuate or curved fractures in this VIS image are located on the eastern margin of Elysium Planitia.

Orbit Number: 52575 Latitude: -0.338087 Longitude: 175.334 Instrument: VIS Captured: 2013-10-20 23:34

Photo credit: NASA/JPL-Caltech/Arizona State University

Yellowknife Bay Geological Formations and Drill Sites

This mosaic of images from Curiosity's Mast Camera (Mastcam) shows geological members of the Yellowknife Bay formation, and the sites where Curiosity drilled into the lowest-lying member, called Sheepbed, at targets "John Klein" and "Cumberland." The scene has the Sheepbed mudstone in the foreground and rises up through Gillespie Lake member to the Point Lake outcrop. These rocks record superimposed ancient lake and stream deposits that offered past environmental conditions favorable for microbial life. Rocks here were exposed about 70 million years ago by removal of overlying layers due to erosion by the wind.

The 50-centimeter scale bars at different locations in the image are about 20 inches long. The lower scale bar is about 26 feet (8 meters) away from where Curiosity was positioned when the view was recorded. The upper scale bar is about 98 feet (30 meters) from the rover's location. The scene is a portion of a 111-image mosaic acquired during the 137th Martian day, or sol, of Curiosity's work on Mars (December 24, 2012). The foothills of Mount Sharp are visible in the distance, upper left, southwest of camera position.

Image credit: NASA/JPL-Caltech/MSSS

Candor Chasma

Shadows cast by the high walls and high hills within Candor Chasma are visible in this image. The Odyssey spacecraft and THEMIS camera are passing over the surface of Mars at a local time near 5 in the afternoon. The sun is close to the western horizon and shadows are being created by tall topographic features.

Orbit Number: 52547 Latitude: -6.7789 Longitude: 290.464 Instrument: VIS Captured: 2013-10-18 14:20

Photo credit: NASA/JPL-Caltech/Arizona State University

Possible Ancient Lake in Gale Crater

This illustration depicts a concept for the possible extent of an ancient lake inside Gale Crater. The existence of a lake there billions of years ago was confirmed from examination of mudstone in the crater's Yellowknife Bay area. For this illustration, the possible extent was estimated by mapping ancient lake and stream deposits and recognizing that water flowed from the crater rim into the basin (arrows). The water would have pooled in the linear depression created between the crater rim and Mt. Sharp. The area's history likely included the coming and going of multiple lakes of different sizes as climate conditions evolved.

The base map combines image data from the Context Camera on NASA's Mars Reconnaissance Orbiter and color information from Viking Orbiter imagery. The 25-kilometer scale bar at lower right is 15.5 miles long. North is up.

Image credit: NASA/JPL-Caltech/MSSS

Note: For more information, see PIA17594: View into 'John Klein' Drill Hole in Martian Mudstone, PIA17598: Clay Mineral Structure Similar to Clays Observed in Mudstone on Mars, PIA17599: Volatiles Released by Heating Sample Powder from Martian Rock 'Cumberland', and NASA Curiosity: First Mars Age Measurement and Human Exploration Help.

Dune Field in Olympia Undae

Today's VIS image shows another portion of the large dune field near the north polar cap.

Orbit Number: 52489 Latitude: 81.5273 Longitude: 162.846 Instrument: VIS Captured: 2013-10-13 21:01

Photo credit: NASA/JPL-Caltech/Arizona State University

Mars 360: The North Pole

Enjoy views of the martian north pole from all angles in this new animation from ESA’s Mars Express.

The ice cap has a diameter of about 1000 km and consists of many thin layers of ice mixed with dust that extend to a depth of around 2 km below the cap. The prominent gap in the ice cap is a 318 km-long, 2 km-deep chasm called Chasma Boreale.

The layers result from variations in the orbit and rotation of Mars that affect the amount of sunlight received at the poles, and thus the amount of melting and deposition of materials over time. Meanwhile, strong prevailing winds are thought to be responsible for shaping the spiral troughs.

The polar ice cap in this movie was constructed using data provided by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument, MARSIS.

Low-frequency radio waves beamed towards the surface are reflected back to Mars Express from the planet’s surface and from interfaces between layers of different materials underground.

The strength and timing of the radar echoes are a gauge of the depths of different types of interfaces, such as between rock, water or ice. This information can then be translated into 3D views, as seen in this movie.

Video credit: ESA/ASI/NASA/JPL/La Sapienza University/INAF (A. Frigeri)

Dunes in Olympia Undae

The sand dunes in this VIS image are located near the north polar cap. It is springtime and the dunes will darken with time as the winter frost sublimates in the sun.

Orbit Number: 52488 Latitude: 81.0121 Longitude: 190.215 Instrument: VIS Captured: 2013-10-13 19:18

Photo credit: NASA/JPL-Caltech/Arizona State University

Slope Streaks in Terra Sabaea

Numerous dark slope streaks are located on the inner rim of this unnamed crater in Terra Sabaea.

Orbit Number: 52480 Latitude: 0.505546 Longitude: 34.1236 Instrument: VIS Captured: 2013-10-13 03:57

Photo credit: NASA/JPL-Caltech/Arizona State University

Ithaca Rock

The rock "Ithaca" shown here, with a rougher lower texture and smoother texture on top, appears to be a piece of the local sedimentary bedrock protruding from the surrounding soil in Gale Crater. NASA's Curiosity Mars rover used its Mast Camera (Mastcam) to take this image during the 439th Martian day, or sol, of Curiosity's work on Mars (October 30, 2013). The black-outline rectangle indicates the area where the rover's Chemistry and Camera instrument (ChemCam) used its laser and remote micro-imager to inspect Ithaca. That inspection included the 100,000th laser shot fired by ChemCam on Mars. The 0.1 meter scale bar at lower left is about 4 inches.

Photo credit: NASA/JPL-Caltech/MSSS

Note: For more information, see PIA17591: Target for 100,000th Laser Shot by Curiosity on Mars, PIA17593: ChemCam Spectrum from Martian Rock Target 'Ithaca', and Laser Instrument on NASA Mars Rover Tops 100,000 Zaps.

Slope Streaks in Terra Sabaea

Dark slope streaks mark the inner rim of this unnamed crater in Terra Sabaea.

Orbit Number: 52468 Latitude: 0.339369 Longitude: 20.0279 Instrument: VIS Captured: 2013-10-12 04:15

Photo credit: NASA/JPL-Caltech/Arizona State University

Climbing Murray Ridge

After driving uphill about 139 feet (42.5 meters) during the 3,485th Martian day, or sol, of its work on Mars (November 12, 2013), NASA's Mars Exploration Rover Opportunity captured this image with its navigation camera. The climb ascended "Murray Ridge" above "Solander Point" on the western rim of Endeavour Crater.

The view is toward the north-northeast. The distance between the two parallel tracks is about 3.3 feet (1 meter). This sol's drive brought Opportunity's cumulative driving distance to 24.01 miles (38.64 kilometers).

Photo credit: NASA/JPL-Caltech

Lava Channels West of Elysium Mons

The channels and linear depression in this VIS image are located on the western margin of the Elysium Volcanic complex. The channels were created by lava flow.

Orbit Number: 52464 Latitude: 29.9196 Longitude: 139.502 Instrument: VIS Captured: 2013-10-11 20:12

Photo credit: NASA/JPL-Caltech/Arizona State University

Opportunity's Traverse Map Through Sol 3486

NASA's Mars Exploration Rover Opportunity has been working on Mars since landing inside Eagle Crater on January 25, 2004 (Universal Time; evening of January 24, Pacific Standard Time). The gold line on this image shows Opportunity's route from the landing site, in upper left, to the area it is investigating on the western rim of Endeavour Crater as the date approaches for the rover's 10th anniversary on Mars, in Earth years.

The map shows Opportunity's location as of the 3,486th Martian day, or sol, of its exploration of Mars (November 13, 2013). By that sol, it had driven 24.01 miles (38.64 kilometers) and was ascending "Murray Ridge" above "Solander Point" on the rim of Endeavour Crater. The features are all within the Meridiani Planum region of equatorial Mars, which was chosen as Opportunity's landing area because of earlier detection of the mineral hematite from orbit.

The base image for the map is a mosaic of images taken by the Context Camera on NASA's Mars Reconnaissance Orbiter. The 5-kilometer scale bar is 3.1 miles long, and the diameter of Endeavour Crater is about 14 miles (22 kilometers). North is up.

Opportunity completed its three-month prime mission in April 2004 and has continued operations in bonus extended missions. It has found several types of evidence of ancient environments with abundant liquid water. The Mars Reconnaissance Orbiter reached Mars in 2006, completed its prime mission in 2010, and is also working in an extended mission.

Image credit: NASA/JPL-Caltech/MSSS/NMMNHS

Daedalia Planum

Today's VIS image shows a small portion of the lava flows that comprise Daedalia Planum.

Orbit Number: 52449 Latitude: -20.3058 Longitude: 233.727 Instrument: VIS Captured: 2013-10-10 12:05

Photo credit: NASA/JPL-Caltech/Arizona State University

Lava Channel East of Olympus Mons

The channel in the bottom part of this VIS image was created by lava flow rather than water flow. This feature is located in the Tharsis plains east of Olympus Mons.

Orbit Number: 52423 Latitude: 20.9613 Longitude: 240.14 Instrument: VIS Captured: 2013-10-08 11:01

Photo credit: NASA/JPL-Caltech/Arizona State University

Rubicon Valles

Today's VIS image shows part of Rubicon Valles located on the northwestern flank of Alba Mons.

Orbit Number: 52423 Latitude: 44.6535 Longitude: 244.022 Instrument: VIS Captured: 2013-10-08 11:00

Photo credit: NASA/JPL-Caltech/Arizona State University

Surface Textures Southeast of Aeolis Planum

The surface textures in this VIS image located southeast of Aeolis Planum likely had wind action as one of the contributing processes.

Orbit Number: 52402 Latitude: -7.56114 Longitude:150.354 Instrument: VIS Captured: 2013-10-06 15:59

Photo credit: NASA/JPL-Caltech/Arizona State University

Nicholson Crater

This VIS image shows part of the large deposit on the floor of Nicholson Crater.

Orbit Number: 52387 Latitude: 0.130557 Longitude: 194.999 Instrument: VIS Captured: 2013-10-05 12:18

Photo credit: NASA/JPL-Caltech/Arizona State University

Hydraotes Chaos

The ridges and mesas in this VIS image are part of Hydraotes Chaos.

Orbit Number: 52370 Latitude: 1.85829 Longitude: 325.257 Instrument: VIS Captured: 2013-10-04 02:43

Photo credit: NASA/JPL-Caltech/Arizona State University

Textured Mesa Southeast of Bosporus Planum

Also imaged by MRO's Context Camera, this observation shows one of two odd, rounded mesas with a knobby/pitted texture.

This mesa may be the last remnants of a formerly more extensive geologic unit. Given the particular pitted texture, this formation could be ice-rich.

High resolution images can greatly help to characterize the surface texture and allow us to compare other mid-latitude-type landforms, which may have some connection with ice and sublimation degradation processes.

Photo credit: NASA/JPL/University of Arizona

Note: These mesas are located southeast of Bosporus Planum. For more information, see PIA17703: A Textured Mesa.

Intersection of Fractures in Echus Chasma

In this image, we see an intersection of several fractures on the floor of Echus Chasma. One "sector" appears to have been filled by a more recent viscous lava flow.

Echus Chasma is considered to be the water source region that formed Kasei Valles, a large valley that extends thousands of kilometers to the north. HiRISE may help determine the relative roles of lava and water in the region.

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see PIA17704: Martian Intersection.

Coprates Chasma

Today's VIS image shows part of Coprates Chasma.

Orbit Number: 52347 Latitude: -13.3246 Longitude: 295.016 Instrument: VIS Captured: 2013-10-02 03:24

Photo credit: NASA/JPL-Caltech/Arizona State University

Nirgal Vallis Tributaries

Nirgal Vallis is one of the largest and longest valley networks on Mars (approximately 400 kilometers in length). Oriented roughly east-west and located north of the Argyre impact basin, its western region contains numerous short, theater-headed tributaries that merge into a long, sinuous, and deeply entrenched main valley that extends eastward to Uzboi Vallis.

The area in this image (centered at -27.1730 latitude, 313.7340 longitude) is of the western most tributaries. Valley heads are steep and abrupt with blunt terminations. Although Nirgall Vallis formed long ago, likely by flowing water, abundant wind-blown sediments transformed into the dune fields that now line the valley floors. However, the distinctive valley pattern shape with steep walls and flat floors led many to propose that ground water flowed out to the surface along the valley heads and walls of the numerous tributaries. This process, known as sapping, begins with ground water flowing along subsurface fractures or permeable layers and carrying out sediments with it as it emerges at the cliff face.

Eventually, the loss of support from beneath undermines the cliff face, causing it to slump into the valley. With continued sapping, tributaries grow progressively in a headward direction. This kind of erosion is common in the Colorado Plateau of the Southwestern United States and helped form the distinctive shape of the Grand Canyon. Wrinkle ridges intersecting several tributaries may have provided additional avenues for ground water flow into the valley system.

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see PIA17701: Nirgal Vallis Tributaries.

Gale Crater

This VIS image of Gale Crater shows the region of the crater that is "home" to the Curiosity Rover.

Orbit Number: 52340 Latitude: -4.58873 Longitude: 137.411 Instrument: VIS Captured: 2013-10-01 13:32

Photo credit: NASA/JPL-Caltech/Arizona State University

Hydrated Sulfate Landslides in Ophir Chasma

Giant landslides in Ophir Chasma host a variety of geologic surfaces and mineralogies. Some possess a variety of hydrated sulfate minerals that formed in the presence of partially acidic liquid water.

This image of an ancient, approximately 3 billion year-old landslide shows two distinct surface albedos, which are proportions of reflected light. These different toned surfaces also mark a transition from one sulfate mineralogy to another and variations in surface evolution.

The upper slopes to the north are light-toned due to an abundance of hydrated sulfate minerals and bright surface dust. The surfaces that make up the southern portions of the landslide are darker in tone due to the greater frequency of dark sediment that form strings of sand drifts. Additionally, the underlying units of bedrock consist of darker minerals with less hydration then those to the north, implying a change in the ancient aqueous environments that formed them.

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see PIA17702: Hydrated Sulfate Landslides in Ophir Chasma.

Iani Chaos

Several different surface textures are present on the lower elevations of Iani Chaos.

Orbit Number: 52283 Latitude: -0.827418 Longitude: 341.65 Instrument: VIS Captured: 2013-09-26 20:57

Photo credit: NASA/JPL-Caltech/Arizona State University

Murray Ridge on the Rim of Endeavour Crater

This scene shows the "Murray Ridge" portion of the western rim of Endeavour Crater on Mars. The ridge is the NASA's Mars Exploration Rover Opportunity's work area for the rover's sixth Martian winter.

The ridge rises about 130 feet (40 meters) above the surrounding plain, between "Solander Point" at the north end of the ridge and "Cape Tribulation," beyond Murray Ridge to the south. This view does not show the entire ridge. The visible ridge line is about 10 meters (33 feet) above the rover's location when the component images were taken.

The scene sweeps from east to south. The planar rocks in the foreground at the base of the hill are part of a layer of rocks laid down around the margins of the crater rim. At this location, Opportunity is sitting at the contact between the Meridiani Planum sandstone plains and the rocks of the Endeavour Crater rim. On the upper left, the view is directed about 22 kilometers (14 miles) across the center of Endeavour crater to the eastern rim.

Opportunity landed on Mars in January 2004 and has been investigating parts of Endeavour's western rim since August 2012.

The scene combines several images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the 3,446th Martian day, or sol, of the mission's work on Mars (October 3, 2013) and the following three sols. On Sol 3451 (October 8, 2013), Opportunity began climbing the ridge. The slope offers outcrops that contain clay minerals detected from orbit and also gives the rover a northward tilt that provides a solar-energy advantage during the Martian southern hemisphere's autumn and winter.

The rover team chose to call this feature Murray Ridge in tribute to Bruce Murray (1931-2013), an influential advocate for planetary exploration who was a member of the science teams for NASA's earliest missions to Mars and later served as director of NASA's Jet Propulsion Laboratory, in Pasadena.

This view is presented in approximately true color, merging exposures taken through three of the Pancam's color filters, centered on wavelengths of 753 nanometers (near-infrared), 535 nanometers (green) and 432 nanometers (violet).

Image credit: NASA/JPL-Caltech/Cornell/Arizona State University

Note: For more information, see PIA17583: 'Murray Ridge' on Rim of Endeavour Crater on Mars, False Color, PIA17585: Opportunity's View Climbing 'Murray Ridge', PIA17586: A New Perspective on Murray Ridge, PIA17588: 'Murray Ridge' in Stereo from Mars Rover Opportunity, and Mars Rover Teams Dub Sites in Memory of Bruce Murray.

Wind Streaks in Syrtis Major Planum

This image shows several wind streaks in Syrtis Major Planum.

Orbit Number: 52279 Latitude: 9.12948 Longitude: 69.5053 Instrument: VIS Captured: 2013-09-26 14:58

Photo credit: NASA/JPL-Caltech/Arizona State University

Ismeniae Fossae Perspective

Branches in the 2 km-wide trough of Ismeniae Fossae are seen in close-up detail in this scene. Material in the channels likely derived from the walls subsequently transported by glaciers or water flowing through the region. Smaller dendritic valley systems formed by water – possibly from melting ice – are seen at the bottom left and in the upper right portion of the image. The clusters of circular to elliptical depressions in the bottom left may be either secondary impact craters from debris flung out by larger impact craters, or collapse pits caused by the sublimation of subsurface ice.

This region was imaged by the High Resolution Stereo Camera on ESA’s Mars Express on 16 June 2013 (orbit 11709), with a ground resolution of about 20 m per pixel. The scene is located at approximately 40°N / 42°E.

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Lava Flows in Daedalia Planum

This VIS image shows a small portion of the lava flows that comprise Daedalia Planum.

Orbit Number: 52274 Latitude: -22.4732 Longitude: 238.098 Instrument: VIS Captured: 2013-09-26 03:18

Photo credit: NASA/JPL-Caltech/Arizona State University

Ismeniae Fossae

This scene shows a section of Ismeniae Fossae that straddles the southern highlands–northern lowlands of Mars. The 2 km-wide curvilinear trough that runs through this image contains numerous parallel grooves and ridges comprising material from the trough walls and material that has been dragged along the floor by ancient glaciers and ice-rich flows.

In the left portion of the scene the channel truncates a roughly 25 km-wide crater. Material in the crater walls has slumped down into the channel, smoothing over the grooved floor.

Around this crater, and elsewhere in Ismeniae Fossae, clusters of circular to elliptical, partially interconnected depressions are observed. These may be either secondary impact craters from debris flung out by larger impact craters, or collapse pits caused by the sublimation of subsurface ice.

The western portion of the 138 km-wide Moreux Crater is seen in the bottom right of the image. Numerous small dendritic valley systems west of the crater provide further evidence of water flowing in this region at some point in the Red Planet’s past, perhaps as water melting from the ice thought to have once covered this region.

The image was taken by the High Resolution Stereo Camera on ESA’s Mars Express on 16 June 2013 (orbit 11709), with a ground resolution of about 20 m per pixel. The image centre is at approximately 40°N / 42°E.

Photo credit: ESA/DLR/FU Berlin (G. Neukum)

Impact Crater with Ring Trough in Utopia Rupes

Does this observation show a possible proto-pedestal crater?

This crater has a ring trough, but the inner circle around the crater does not appear significantly elevated. Why did the ring around the crater collapse before anything else? Could it be an example of ice sublimating from below the surface?

A high resolution image shows us better details, as we can see in this close-up.

Photo credit: NASA/JPL/University of Arizona

Lava Rafts in Athabasca Valles

This image covers part of the Athabasca Valles flood lava plain, the youngest large lava flow on the surface of Mars.

At this location, there are two rafted pieces of lava crust with strange infrared properties. Compared to the rest of the lava flow, these two raised areas are cold at night and warm in the day. This property of the surface, where the temperature changes quickly, is called "low thermal inertia." Rocks tend to have relatively high thermal inertia, so this is unexpected.

This image confirms speculation from earlier, lower resolution images. The rafts are composed of broken up (brecciated) lava, forming an extraordinarily rough surface. Normally, such a jagged pile of lava rocks would have high thermal inertia. But in this location, the rough surface has served as a trap for wind-carried dust. Thus in these rafts, and only in these rafts, is the lava covered by a thick pile of fluffy dust.

Such dust is extremely insulating, meaning that all the solar heating is deposited in a very thin layer near the surface. Therefore, dust gets relatively hot during the day. Because the heat is deposited so shallowly, it is easily lost at night. So, the trapped dust is the explanation for the low thermal inertia of these lava rafts.

Photo credit: NASA/JPL/University of Arizona

Wind Streaks in Syrtis Major Planum

Today's VIS image shows wind streaks in Syrtis Major Planum.

Orbit Number: 52254 Latitude: 5.90248 Longitude: 69.7373 Instrument: VIS Captured: 2013-09-24 13:03

Photo credit: NASA/JPL-Caltech/Arizona State University

Sandstone Cliffs and Hematite Lag Deposits in Ophir Mensa

This target was one of the first close HiRISE views of the enigmatic Valles Marineris interior layered deposits. These light-toned sedimentary deposits are of interest to scientists because they are partially composed of minerals like hematite that likely formed in the presence of liquid water.

The lighter-tone linear units to the north are called "yardangs" and formed when downslope winds carved the fragile sandstone into channels. Over time, wind and gravity conspire to erode material downslope and onto the canyon floor. The darker-toned sandy deposits at the cliff base contain high concentrations of hematite (along with basaltic or volcanic sand) known from infrared orbital measurements.

HiRISE resolution can clearly show outcrops mass wasting finer materials out, and darker layers that are likely hematite-bearing units. This is an excellent candidate for what's called a "hematite lag deposit," where more resistant iron-rich hematite concretions have weathered out of the brittle mesa driven by gravity and wind, similar to that observed at the Mars Exploration Rover Opportunity landing site.

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see PIA17691: Sandstone Cliffs and Hematite Lag Deposits of Ophir Mensa.

Rabe Crater Dunes

This VIS image shows part of the sand sheet and dunes on the floor of Rabe Crater.

Orbit Number: 52231 Latitude: -43.6577 Longitude: 34.2642 Instrument: VIS Captured: 2013-09-22 14:29

Photo credit: NASA/JPL-Caltech/Arizona State University

Linear Ridges Near Nilosyrtis Mensae

Straight and meandering thin ridges are periodically found on Mars. Such ridges can form in a variety of ways.

Rivers beneath glaciers can deposit rocks and sand leaving a raised ridge, called an esker, when the glacier retreats. Sometimes sandy river beds can become cemented by minerals. Later when the river is gone and the uncemented soils next to the old river bed are eroded more easily, the old river bed itself is left standing.

In this observation, relatively straight and narrow ridges are found crisscrossing the slopes between rocky mesas and adjacent valleys. That these ridges extend along steep slopes is unlike the water-born ridges mentioned above. Additionally, some ridges appear to connect through the mesa and extend also down the opposite slope. These features of the ridges suggest that they cut deep into the interior of the mesas.

A ridge of volcanic rock called a dike occurs when magma is squeezed into a deep fracture in the surrounding rock and upward to (or near) the surface. This magma cools and solidifies into a strong rock that resists erosion better than the fracture rock the magma squeezed into earlier. When erosion of these rocks occurs, the harder volcanic rock is left standing as a ridge and reveals the underground plumbing system of the volcanic vent.

Photo credit: NASA/JPL/University of Arizona

Note: These ridges are located in a channel leading to Nilosyrtis Mensae in far northern Arabia Terra.

Delta Deposit at Ismenius Cavus

Today's VIS image shows a delta deposit where a tributary channel enters Ismenius Cavus in Mamers Valles.

Orbit Number: 52206 Latitude: 33.891 Longitude: 17.5017 Instrument: VIS Captured: 2013-09-20 14:40

Photo credit: NASA/JPL-Caltech/Arizona State University

Murray Buttes at the Foot of Mount Sharp

This view taken from orbit shows a cluster of small, steep-sided knobs called "Murray Buttes," on the planned route for NASA's Mars rover Curiosity to reach the slopes of Mount Sharp.

The scene covers a patch of ground about 0.8 mile (1.3 kilometers) across. North is up. The largest buttes in the group are about the size of a football field and the height of a goal post. Darker ground at upper right and lower left is part of sand dunes along the northern edge of Mount Sharp, within Gale Crater. Murray Buttes is located at a gap in that band of dunes, making passage through this area an attractive access route to the mountain slopes just south of this scene.

Curiosity's science team chose the informal name Murray Buttes in tribute to Bruce Murray (1931-2013), an influential advocate for planetary exploration who was a member of the science teams for NASA's earliest missions to Mars and later served as director of NASA's Jet Propulsion Laboratory.

Image credit: NASA/JPL-Caltech

Note: For more information, see Mars Rover Teams Dub Sites in Memory of Bruce Murray.

Rabe Crater Dunes

This VIS image shows part of the sand sheet and dunes on the floor of Rabe Crater.

Orbit Number: 52206 Latitude: -43.6487 Longitude: 34.9565 Instrument: VIS Captured: 2013-09-20 13:07

Photo credit: NASA/JPL-Caltech/Arizona State University

MAVEN: What Happened to Mars?

Billions of years ago when the planets of our solar system were still young, Mars was a very different world. Liquid water flowed in long rivers that emptied into lakes and shallow seas. A thick atmosphere blanketed the planet and kept it warm. In this cozy environment, living microbes might have found a home, starting Mars down the path toward becoming a second life-filled planet next door to our own.

But that's not how things turned out.

Today, Mars is bitter cold and desiccated. The planet's thin, wispy atmosphere provides scant cover for a surface marked by dry riverbeds and empty lakes. If Martian microbes still exist, they're probably eking out a meager existence somewhere beneath the dusty Martian soil.

What happened? This haunting question has long puzzled scientists. To find the answer, NASA is sending a new orbiter to Mars called MAVEN (Mars Atmosphere and Volatile Evolution).

"The goal of MAVEN is to figure out what processes were responsible for those changes in Martian climate," says Bruce Jakosky, Principal Investigator for MAVEN at the University of Colorado at Boulder.

Scheduled for launch in November 2013, and due to arrive in September 2014, MAVEN is bristling with instruments to study Mars’ upper atmosphere. That's where many researchers believe the answer lies.

The only way Mars could have been wet and warm 4 billion years ago, is if it also had a thick atmosphere. CO2 in the Martian atmosphere is a greenhouse gas, just as it is in our own atmosphere. A thick blanket of CO2 and other greenhouse gases would have provided the warmer temperatures and greater atmospheric pressure required to keep liquid water from freezing solid or boiling away.

Something caused Mars to lose that blanket. One possibility is the solar wind. Unlike Earth, Mars is not protected by a global magnetic field. Instead, it has “magnetic umbrellas” scattered around the planet that shelter only part of the atmosphere. Erosion of exposed areas by solar wind might have slowly stripped the atmosphere away over billions of years. Recent measurements of isotopes in the Martian atmosphere by Mars rover Curiosity support this idea: light isotopes of hydrogen and argon are depleted compared to their heavier counterparts, suggesting that they have floated away into space.

Scientists have also speculated that the planet's surface might have absorbed the CO2 and locked it up in minerals such as carbonate. However, this theory has faded in recent years as Mars rovers and orbiters have failed to find enough carbonate to account for the missing gas.

MAVEN will be the first mission to Mars specifically designed to help scientists understand the ongoing escape of CO2 and other gases into space. The probe will orbit Mars for at least one Earth-year. At the elliptical orbit's low point, MAVEN will be 125 km above the surface; its high point will take it more than 6000 km out into space. MAVEN's instruments will track ions and molecules in this broad cross-section of the Martian atmosphere, thoroughly documenting the flow of CO2 and other molecules into space for the first time.

Once Jakosky and his colleagues know how quickly Mars is losing CO2 right now, they can extrapolate backward in time to estimate the total amount lost during the last four billion years. "MAVEN will determine if loss to space was the most important player in driving Martian climate change," Jakosky says.

In the grand scheme of the Solar System, Earth orbits alongside a world that began with as much promise for life as our own … yet turned out so differently. After all these years, MAVEN could write the final chapter in a haunting planetary mystery.

Video credit: NASA

Linear Depressions in Memnonia Fossae

The linear depressions in this VIS image are part of Memnonia Fossae.

Orbit Number: 52200 Latitude: -21.509 Longitude: 211.495 Instrument: VIS Captured: 2013-09-20 01:09

Photo credit: NASA/JPL-Caltech/Arizona State University

Barchan Dunes on the Western Rim of Hellas Planitia

Sand dunes such as those seen in this image have been observed to creep slowly across the surface of Mars through the action of the wind. These are a particular type of dune called a "barchan," which forms when the wind blows in one direction (here, east to west) for long periods of time. Barchan dunes are common on Mars and in the desert regions of the Earth.

These barchan dunes are located on the western rim of the Hellas impact basin, in the Southern hemisphere of Mars. This area is covered by extensive deposits of layered rocks that were initially deposited as loose sediments and over time formed these rock layers. Portions of these layered rocks were subsequently eroded away and the remaining layers now form numerous flat-topped hills called "mesas." The barchan dunes are forming in the lee (downwind) of the mesas.

This area was previously image by HiRISE in 2008 (PSP_007676_1385) and was retargeted here through a public request (http://www.uahirise.org/hiwish). Careful comparison of repeat images such as these can reveal the speed and manner by which dunes move across the Martian surface. This information can be used to study the current atmosphere of Mars, the age and mobility of sand deposits on the planet's surface, and the hazards that sand dunes may pose to landed vehicles such as rovers.

Over the course of its mission, the science instruments on board the Mars Reconnaissance Orbiter (MRO) have returned over 200 terabits of data back to Earth. This image was taken on November 4, 2013, the same day that MRO's 200-terabit mark was surpassed.

Photo credit: NASA/JPL-Caltech/University of Arizona

Possible Shoreline in Southern Isidis Planitia

This area--known as the Deuteronilus contact of the Isidis Basin--has been interpreted as a possible ancient shoreline. There are also suggestions that this contact is of volcanic origin.

One direct benefit of a high resolution image is the ability to monitor the detailed morphology of the contact to help to determine whether this formation is the result of an ocean or of a volcanic filling of the Isidis Basin.

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see PIA17671: Hints of an Ancient Shoreline in Southern Isidis Planitia.

Breached Crater Rim in Coloe Fossae

This image shows an impact crater with a diameter of approximately 2 kilometers located in the Coloe Fossae region of Mars.

It is partially filled with a sediment flow that has breached the south rim and continues northwards for approximately 4 kilometers before abruptly terminating in a rounded lobe of blocky material.

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see PIA17672: Breached Rim of a Circular Depression.