Wednesday, November 19, 2014

Pink Cliffs

This small ridge, about 3 feet (1 meter) long, appears to resist wind erosion more than the flatter plates around it. Such differences are among the rock characteristics that NASA's Curiosity Mars rover is examining at selected targets at the base of Mount Sharp.

The ridge pictured here, called "Pink Cliffs," is within the "Pahrump Hills" outcrop forming part of the basal layer of the mountain. This view is a mosaic of exposures acquired by Curiosity's Mast Camera (Mastcam) shortly before a two-week walkabout up the outcrop, scouting to select which targets to examine in greater detail during a second pass.

Pink Cliffs is one of the targets chosen for closer inspection. This image combines several frames taken with the Mastcam on October 7, 2014, the 771st Martian day, or sol of Curiosity's work on Mars. The color has been approximately white-balanced to resemble how the scene would appear under daytime lighting conditions on Earth.

Figure 1 is a version with a scale bar overlaid on the image.

An image showing the Pahrump Hills walkabout route is at PIA19039. An overhead map showing the walkabout drives, from Sol 780 (Oct. 16) to Sol 794 (Oct. 30) is at

Image credit: NASA/JPL-Caltech/MSSS

Sunday, November 16, 2014

Spring in Inca City II

It is about two weeks later in Inca City and the season is officially spring. Numerous changes have occurred. Large blotches of dust cover the araneiforms. Dark spots on the ridge show places where the seasonal polar ice cap has ruptured, releasing gas and fine material from the surface below.

At the bottom of the image fans point in more than one direction from a single source, showing that the wind has changed direction while gas and dust were flowing out. Was the flow continuous or has the vent opened and closed?

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18893: Spring in Inca City II.

Saturday, November 15, 2014

Spring in Inca City I

Every winter a layer of carbon dioxide ice — or, dry ice — condenses in the Southern polar region, forming a seasonal polar cap less than 1 meter deep. Early in the spring the ice layer begins to sublimate (going directly from a solid to gas) from the top and bottom of the ice layer. Under the ice gas pressure builds up until a weak spot in the ice layer ruptures. The gas rushes out and as it escapes it erodes a bit of the surface.

Fine particles are carried by the gas to the top of the ice and then fall out in fan-shaped deposits. The direction of the fan shows the direction either of the wind or down the slope. If the wind is not blowing a dark blotch settles around the spot the gas escaped.

This region is known informally as Inca City, and it has a series of distinctive ridges. On the floor between the ridges are radially organized channels, known colloquially as spiders, more formally called "araneiforms." The channels have been carved in the surface over many years by the escaping pressurized gas. Every spring they widen just a bit.

This was the first image to be acquired after the sun rose on Inca City, marking the end to polar night. A few fans are visible emerging from the araneiforms.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18892: Spring in Inca City I.

Sunday, November 2, 2014

Partially-Filled Impact Crater in Elysium Planitia

This image shows an impact crater that was cut by lava in the Elysium Planitia region of Mars. The relatively flat, shallow floor, rough surface texture, and possible cooling cracks seem to indicate that the crater was partially filled with lava. The northern part of the image also shows a more extensive lava flow deposit that surrounds the impact ejecta of the largest impact crater in the image.

Which way did the lava flow? It might appear that the lava flowed from the north through the channel into the partially filled crater. However, if you look at the anaglyph with your red and blue 3D glasses, it becomes clear that the partially filled crater sits on top of the large crater's ejecta blanket, making it higher than the lava flow to the north. Since lava does not flow uphill, that means the explanation isn't so simple.

We have seen much evidence for lava flows in this region that flowed to much higher levels than the present surface, then deflated or drained away. That may have happened here: lava flowed from from north to south to fill this crater, but then it drained back to the north, carving this channel.

The topographic information that we gained from having a stereo pair let us answer a question that we could not have with only a single image. This is a great example of why we take stereo images, where the two images are used to make a 3D image.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18887: Which Way is Up?

Saturday, November 1, 2014

Hardened Dunes in Arcadia Planitia

HiRISE, with its high resolution and 8 years in orbit about Mars, has shown that many dunes and ripples on the planet are active. This demonstrates that in some areas sand is loose enough and winds strong enough, that significant change can occur.

Nevertheless, other Martian dunes are clearly *inactive*. This image in Arcadia Planitia shows dunes in a crater. Unlike active dunes on the planet, those here are bright, and, zooming in, there are several lines of evidence indicating that the dunes have become indurated, that is, hardened into cohesive sediment or even into sandstone rock. For example, the dune field at the southern edge is cut off by a step cliff, indicating erosion of hard material. Although fine scale ripples on the original dune surface are preserved, we also see large scale fluting from southwest to northeast, a common texture associated with wind-induced sand abrasion.

How these dunes became indurated is unknown. One possibility is that this area of Mars was buried and then exhumed, a process that seems to have occurred many times in the Martian past over various areas of the planet. During burial, compaction and possibly ground water circulation would have indurated the dunes, leaving them as a hard sandstone that, when exhumed, was subsequently partially eroded.

Note: a version of the cutout is with only the scale bar is here.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18890: Hardened Dunes in Arcadia Planitia.

Friday, October 31, 2014

Sand Forming at a Channel in Athabasca Valles

This image shows a small channel cutting into young volcanic lavas in a region where massive catastrophic flooding took place in the relatively recent past. The Athabasca Valles region includes a vast lava flow, thought to be the youngest on Mars, with even younger outflow channels that were carved by running water. The source of the water is believed to be the Cerberus Fossae valleys to the north, which may have penetrated to an over-pressurized aquifer in the subsurface.

Nowadays, erosion by gravity, wind, and frost gradually wears down the rims of the outflow channels. In this scene, we see dark materials along the channel rim that were probably exposed by this erosion. The dark materials are less red than the surrounding surface and so they appear blue in this enhanced color picture. Viewed close up, the dark materials show ripples that suggest they are made up of mobile sand. It is possible that this sand originated elsewhere and simply collected where we see it today, but the fact that sand is not found elsewhere in the scene suggest to us that it is eroding out of the volcanic layers at the retreating rim of the channel.

Sand sources are important because mobile sand grains have only a limited lifetime, wearing down and chipping apart each time they impact the surface. Erosion of the volcanic materials in this region may provide sands to replace those that are destroyed. Few such sand sources have so far been identified on Mars.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18889: Sand Sources Near Athabasca Valles.

Thursday, October 30, 2014

Possible Landing Site of the Mars 3 Lander

Despite the recent successes of missions landing on Mars, like the Mars Science Laboratory (Curiosity) or the arrival of new satellites, such as India's MOM orbiter, the Red Planet is also a graveyard of failed missions.

The Soviet Mars 2 lander was the first man-made object to touch the surface of the Red Planet when it crashed landed on 27 November 1971. It is believed that the descent stage malfunctioned after the lander entered the atmosphere at too steep an angle. Attempts to contact the probe after the crash were unsuccessful.

HiRISE acquired this image to aid in the search for the missing lander. If the Mars 2 debris field is found it could serve as a future landing location for a mission to study the effects of crash landing on the Martian surface and effects of aging on man-made objects.

This caption is based on the original science rationale. To date, the debris field has not been located, but this spot was noted as a probable location for the Mars 3 lander.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18888: Search for the Mars 2 Debris Field. The Mars 3 Lander is believed to have landed in Ptolemaeus Crater.

Friday, October 17, 2014

Wdowiak Ridge

This vista from NASA's Mars Exploration Rover Opportunity shows "Wdowiak Ridge," from left foreground to center, as part of a northward look with the rover's tracks visible at right.

Opportunity's panoramic camera (Pancam) recorded the component images for this mosaic on September 17, 2014, during the 3,786th Martian day, or sol, of Opportunity's work on Mars.

The ridge stands prominently on the western rim of Endeavour crater, about 200 yards or meters west of the rim's main crest line. Its informal name is a tribute to Opportunity science team member Thomas J. Wdowiak (1939-2013).

This panorama spans about 70 compass degrees from north-northwest on the left to east-northeast on the right. Wdowiak Ridge rises steeply about 40 feet from base to top. It extends about 500 feet (150 meters) in length. For scale, the distance between Opportunity's parallel wheel tracks is about 3.3 feet (1 meter).

Wdowiak Ridge is visible from overhead in the map at, from the northeastern end near the rover's Sol 3751 location to Odyssey Crater near the rover's Sol 3789 location.

This version of the image is presented in approximate true color by combing 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 University/Arizona State University

Note: For more information, see PIA18615: Opportunity's Northward View of 'Wdowiak Ridge' (False Color), PIA18616: Opportunity's Northward View of 'Wdowiak Ridge' (Stereo), and NASA's Opportunity Rover Gets Panorama Image at 'Wdowiak Ridge'.

Friday, October 10, 2014

Preparing for Comet Siding Spring (C/2013 A1)

This artist's concept shows NASA's Mars orbiters lining up behind the Red Planet for their "duck and cover" maneuver to shield them from comet dust that may result from the close flyby of comet Siding Spring (C/2013 A1) on October 19, 2014.

The comet's nucleus will miss Mars by about 87,000 miles (139,500 kilometers), shedding material as it hurtles by at about 126,000 miles per hour miles (56 kilometers per second), relative to Mars and Mars-orbiting spacecraft.

NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data. The NASA orbiters at Mars are Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN.

Image credit: NASA/JPL-Caltech

Note: For more information, see PIA18612: View of Comet Siding Spring from Southern Hemisphere (Artist's Concept) and NASA Prepares its Science Fleet for October 19 Mars Comet Encounter.

Wednesday, October 8, 2014

Thumbprint Ridges at Planum Australe

While yesterday's VIS image showed a texture of oval depressions (swiss cheese), today's VIS image shows a linear surface texture of the south polar cap. This texture is described as looking like a thumbprint.

Orbit Number: 56378 Latitude: -77.7252 Longitude: 184.825 Instrument: VIS Captured: 2014-08-29 21:37

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