Friday, December 23, 2011

Valley in Ismenius Lacus Region

A valley extends across the center of the image, and a tributary joins it from the north, while another branch connects from the south. This branch--which resembles half of a crater--is really just a bend in the channel, much more incised than the muted valley going across the scene.

There is evidence of mass wasting (gravity moving dry materials off high-standing regions onto low-lying regions), visible where a series of ridges appear to be piling up near the floor of the bend.

The terrain surrounding the valley has craters of a range of ages, judging by their different states of degradation. One small fresh crater near the right side of the image has dark, high-standing rays extending from it. A larger more degraded crater is located in the bottom third of the image. A great deal of material has flowed off the crater walls into its center. It is likely that ground ice aided the movement of this material.

Photo credit: NASA/JPL/University of Arizona

Note: The location of this image, Ismenius Lacus, lies in the larger region of Arabia Terra and is located northeast of Cerulli Crater.

Wednesday, December 21, 2011

Radargram of Mars' North Polar Plateau

The upper panel is a radargram profile from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), showing data from the subsurface of Mars in the ice-rich north polar plateau of Mars. It shows layers detected to a depth of about 1.5 miles (2.7 kilometers) beneath the surface in a transect about 930 miles (1,500 kilometers) long. A basal unit of a sand- and dust-rich icy material comprises more than half of the bulk of the polar plateau in this radargram profile. Its base can be traced from beneath the Olympia Undae sand sea at left, across the entire polar stack, to the margin of the Rupes Tenuis plateau at right, where there are no overlying north polar layered deposits (NPLD). The vertical dimension is time delay of radio-signal echo. The apparent deepening of the basal unit's lower boundary at the center is an artifact of the slowing of the radar wave in the icy material. In fact, the lower boundary is nearly flat.

The lower panel shows the path of the spacecraft ground track while these radar observations were being made, on a topographical map derived from Mars Orbiter Laser Altimeter data. Total relief in the topography from highest (red) to lowest (purple) is 1.7 miles (2.7 kilometers).

Image credit: ESA/NASA/JPL-Caltech/Univ. of Rome/ASI/GSFC

Note: For more information, see MARSIS Completes Measurement Campaign Over Martian North Pole.

Monday, December 19, 2011

Faults in Ius Chasma

Ius Chasma is one of many steep-sided interconnected depressions (chasmata) that comprise Valles Marineris, the largest canyon system in the Solar System.

The chasma is approximately 900 kilometers long and is located in western Valles Marineris. The floor of Ius Chasma is between 8 to 10 kilometers deep and is divided by a prominent east-west trending ridge known as Geryon Montes.

The region in this image is located (approximately 7.8 degrees South, 279.5 degrees East) on the floor of Ius Chasma. A variety of light and medium-toned terrains and layered units of different rock types comprise the chasma floor. Prominent faults of various sizes have displaced and deformed these layered units and outcrops, some in a spectacular fashion.

The ejecta of small fresh-appearing impact craters formed in the light-toned units reveal the existence of a darker (likely basaltic) underlying substrate. Linear dunes are located on top of the lighter-tone outcropping units and are ubiquitous on the chasma floor. These dunes are oriented in a north-south direction and indicate prevailing westerly winds through the canyon.

Photo credit: NASA/JPL/University of Arizona

Sunday, December 18, 2011

Fresh Crater North of Tharsis Region

This impact crater is approximately one kilometer in diameter. The ejecta blanket (remnants of the material from the original impact) is still visible indicating that the crater may be very fresh.

But what do we mean by the word "fresh," or even "recent," as some craters are described? When talking about craters on Mars, both terms are relative: the impact that created the crater in this observation could have occurred millions of years ago! We can often differentiate between older and younger craters by looking at their rims. A crater rim that appears more defined or sharp, versus one that is clearly eroded, indicates the former is more recent, or "fresh."

The Tharsis region on Mars is home to some of the largest shield volcanoes on the Red Planet, including the largest, Olympus Mons.

This is a stereo pair with ESP_019140_2310.

Photo credit: NASA/JPL/University of Arizona

Saturday, December 17, 2011

Layering in Central Candor Chasma

This HiRISE image shows faulted layered deposits in a part of Valles Marineris called Candor Chasma.

Often faults cut through the layered material in this area, indicating that the rocks underwent stress causing them to crack and shift in position after they were deposited.

This area also has a high abundance of hematite. Hematite is a mineral that can precipitate out of water, so its presence on Mars is of special interest for understanding the distant past.

Photo credit: NASA/JPL/University of Arizona

Friday, December 16, 2011

Spring Fans Bursting from Cracks in Ice

Sand dunes in the north polar region of Mars are covered every winter by a layer of carbon dioxide ice (dry ice). In the springtime the ice on the dunes cracks, often in polygonal patterns.

Once the ice layer has cracked the sand below can escape. It may be blown downwind, landing in fan-shaped deposits on top of the seasonal layer of ice. It may also slide down the sides of the dunes, often the case when the ice ruptures at the crest of the dune.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located in Olympia Undae to the northeast of Dokka Crater.

Wednesday, December 14, 2011

Crater in Utopia Rupes

The objective of this observation is to examine features of a mid-latitude crater.

In the Context Camera (CTX) image (P18_008030_2217) of this area, the crater floor has hollows and a high density of pits. The wall has the shape of the alcoves of gullies with the lower part covered up. Perhaps this crater once had gullies, but is now filled up.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in the Utopia Rupes region of western Utopia Planitia.

Tuesday, December 13, 2011

Meanders and Tributaries in Ridge Form in the Zephyria Region

This observation reveals two obvious features. The smaller, narrow ridges oriented vertically are yardangs, which are created by wind erosion; the wind strips away the surrounding terrain, and the ridges remain because they contain more hardened material.

The second feature—the inverted, meandering channel snaking through the image—is caused by similar processes. This was once a river bed that meandered due to changes in topography. As the river flowed, sediments were deposited on its floor, and over time, these sediments became hardened, so when the wind later stripped away the surrounding terrain, the hardened sediments remained, leaving an inverted form.

Photo credit: NASA/JPL/University of Arizona

Monday, December 12, 2011

Interacting Fossae Segments East of Athabasca Valles

Athabasca Valles starts suddenly along the Cerberus Fossae and flows southwest for approximately 400 kilometers. The source region is divided into two lobes, each roughly centered on the fossae.

Understanding the possible volume and flux of water in the ancient past may help in learning how the flood channel formed.

Photo credit: NASA/JPL/University of Arizona

Sunday, December 11, 2011

Shoemaker Ridge

The feature informally named "Shoemaker Ridge" in the "Cape York" segment of the western rim of Endeavour Crater includes outcrops that are likely impact breccias. Impact breccias are a type of jumbled rock previously examined by NASA's Mars Exploration Rover Opportunity at the "Chester Lake" target on Cape York. The view looks northward toward the southern edge of Shoemaker Ridge.

This image combines exposures taken by Opportunity's Panoramic Camera (Pancam) through three different color filters during the 2,715th Martian day, or sol, of the rover's work on Mars (September 13, 2011). It is presented in false color to emphasize differences among materials in the rock and soil. The filters used are centered on wavelengths of 753 nanometers (near infrared), 535 nanometers (green) and 412 nanometers (violet).

Most of Cape York is covered in densely packed basaltic sands with small embedded rock clasts. Outcrops are exposed particularly on the inboard, or southeast, side of the cape. The name Shoemaker Ridge pays tribute to one of the founding fathers of planetary geology, Eugene Shoemaker.

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

Note: An annotated version of the above image can be found here.

Saturday, December 10, 2011

Homestake Vein

This false-color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum.

"Homestake" is near the edge of the "Cape York" segment of the western rim of Endeavour Crater.

Exposures combined into this view were taken through Pancam filters admitting light with wavelengths centered at 753 nanometers (near infrared), 535 nanometers (green) and 432 nanometers (violet). The view is presented in false color to make some differences between materials easier to see.

The exposures were taken during the 2,769th Martian day, or sol, of Opportunity's career on Mars (November 7, 2011).

Photo credit: NASA/JPL-Caltech/Cornell/ASU

Note: For other pictures of Homestake Vein, see PIA15033: 'Homestake' Vein in Color, PIA15035: Close-up View of 'Homestake' Vein, PIA15036: Western Edge of 'Cape York,' with Bright Vein and Also, see the NASA Science News article, "Slam Dunk" Sign of Ancient Water on Mars.

Update: (3 May 2012) A further discussion of Opportunity at Endeavour Crater and the previously wet climate there (as indicated by the Homestake Vein, shown above) can be found at Paydirt at 8-Year-Old Mars Rover's 'New Landing Site'

Friday, December 9, 2011

Dunes in Vastitas Borealis

This scene is from early spring in the northern hemisphere of Mars. These barchan dunes are covered with a layer of seasonal carbon dioxide ice (dry ice). Bluish cracks in the ice are visible across the top of some of the dunes.

Dark fan-shaped deposits around the edges of the dunes are at spots where the ice has sublimated (gone directly from ice to gas) and the ice layer has ruptured, allowing the sand from the dune to escape out from under the ice. The sand is then free to be blown by the wind.

This image is one product from an observation by the High Resolution Imaging Science Experiment (HiRISE) camera taken on September 30, 2011, at 73.3 degrees north latitude, 355.1 degrees east longitude. Other image products from the same observation are at

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

Tuesday, December 6, 2011

Remnant of Unconformable Deposit in Electris

The Electris region of Mars contains some interesting features, such as the raised-relief blocks of material visible in this image.

One goal of this observation is to try to determine the origin of what's called the "mantling deposit." How was this deposit placed here? What types of geologic processes have acted to form the deposit? An image at high resolution can help provide details on the thickness and subtle variations within this deposit that can give us information on its origin and what erosional processes it has experienced.

This is a stereo pair with ESP_024074_1425.

Photo credit: NASA/JPL/University of Arizona

Note: This image lies in the midst the of the Gorgonum Chaos, which is in Terra Sirenum.

Monday, December 5, 2011

Phlegra Montes

Phlegra Montes is a range of gently curving mountains and ridges on Mars. They extend from the northeastern portion of the Elysium volcanic province to the northern lowlands. The High-Resolution Stereo Camera on ESA’s Mars Express collected the data for these images on 1 June 2011 during orbit 9465. This perspective view has been calculated from the Digital Terrain Model derived from the stereo channels.

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

Note: For more information, see Mountains and Buried Ice on Mars.

Sunday, December 4, 2011

Gullies in Acidalia Planitia

This observation covers gullies that were previously identified in the walls of a crater in a MOC image (E0502675).

Do these gullies have features that can be interpreted as characteristic of snow and/or ice melting? At HiRISE resolution, questions like this can possibly be answered.

HiRISE often re-images areas to track seasonal changes, so we expect to monitor these gullies for changes at intervals during several Mars years.

Photo credit: NASA/JPL/University of Arizona

Note: These gullies are in a crater in Acidalia Planitia, to the northeast of Gamboa Crater.

Saturday, December 3, 2011

Gully and Dunes

An earlier observation (ESP_019969_1215) of the same area shows a very interesting feature: a defrosting gully and dunes, with distinct defrosting spots along the gully channel.

Since HiRISE can re-image certain areas over time, this area seems like a worthwhile place to monitor the defrosting process and hopefully gain a deeper understanding of it. This observation was taken at the end of southern summer and will serve as a baseline for observing the gully defrosting next southern spring.

Photo credit: NASA/JPL/University of Arizona

Note: This image is taken in an unnamed crater southwest of Argyre Planitia.

Friday, December 2, 2011

Bright and Dark Terrain in Noctis Labyrinthus

This image shows the transitional terrain where the linear troughs and rounded pits of Noctis Labyrinthus merge with the larger chasmata of Valles Marineris. Unusual bright blocks can be seen beneath a layered dark mantle.

The bright blocks also have some layering and show hydration features in CRISM spectra. The bright blocks are jagged and irregular in shape, perhaps because they represent impact material or because they are partially obscured beneath a dark mantle so we cannot see their full extent.

The dark mantle consists of aeolian (wind-driven) material (as evidenced by linear ripples) as well as a finely layered unit. The dark layered mantle does not show any hydration features in CRISM spectra so perhaps it represents multiple events of wind deposition where each time this material was laid down it became a distinct layer.

This is a stereo pair with PSP_006692_1740.

Photo credit: NASA/JPL/University of Arizona

Thursday, December 1, 2011

Cross Section of Gale Crater

This artist's impression of Mars' Gale Crater depicts a cross section through the mountain in the middle of the crater, from a viewpoint looking toward the southeast. The rover Curiosity of NASA's Mars Science Laboratory mission will land in Gale Crater in August 2012. The landing area is on or near an alluvial fan indicated in blue. A key factor in selection of Gale as the mission's landing site is the existence of clay minerals in a layer near the base of the mountain, within driving range of the landing site. The location of the clay minerals is indicated as the green band through the cross section of the mountain. The image uses two-fold vertical exaggeration to emphasize the area's topography. The crater's diameter is 96 miles (154 kilometers).

The image combines elevation data from the High Resolution Stereo Camera on the European Space Agency's Mars Express orbiter, image data from the Context Camera on NASA's Mars Reconnaissance Orbiter, and color information from Viking Orbiter imagery.

Image Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS