Saturday, December 20, 2014

Daga Vallis

The THEMIS VIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. Today's false color image shows part of Daga Vallis on Eos Mensa.

Orbit Number: 2012 Latitude: -11.8784 Longitude: 317.167 Instrument: VIS Captured: 2002-05-29 04:14

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

Wednesday, December 17, 2014

Possible Methane Sources and Sinks

This illustration portrays possible ways that methane might be added to Mars' atmosphere (sources) and removed from the atmosphere (sinks). NASA's Curiosity Mars rover has detected fluctuations in methane concentration in the atmosphere, implying both types of activity occur in the modern environment of Mars.

A molecule of methane consists of one atom of carbon and four atoms of hydrogen. Methane can be generated by microbes and can also be generated by processes that do not require life, such as reactions between water and olivine (or pyroxene) rock. Ultraviolet radiation (UV) can induce reactions that generate methane from other organic chemicals produced by either biological or non-biological processes, such as comet dust falling on Mars. Methane generated underground in the distant or recent past might be stored within lattice-structured methane hydrates called clathrates, and released by the clathrates at a later time, so that methane being released to the atmosphere today might have formed in the past.

Winds on Mars can quickly distribute methane coming from any individual source, reducing localized concentration of methane. Methane can be removed from the atmosphere by sunlight-induced reactions (photochemistry). These reactions can oxidize the methane, through intermediary chemicals such as formaldehyde and methanol, into carbon dioxide, the predominant ingredient in Mars' atmosphere.

Image credit: NASA/JPL-Caltech/SAM-GSFC/University of Michigan

Note: For more information, see:
* PIA19086: Tunable Laser Spectrometer on NASA's Curiosity Mars Rover
* PIA19087: Methane Measurements by NASA's Curiosity in Mars' Gale Crater
* PIA19089: Some Data from Detection of Organics in a Rock on Mars
* PIA19090: Comparing 'Cumberland' With Other Samples Analyzed by Curiosity
* PIA19091: Mars Has Ways to Make Organics Hard to Find
* NASA Rover Finds Active and Ancient Organic Chemistry on Mars
* How NASA Curiosity Instrument Made First Detection of Organic Matter on Mars
* Curiosity Detects Methane Spike on Mars

Friday, December 12, 2014

Impact Crater in Morava Valles

Morava Valles is a small outflow channel in the Margaritifer Sinus region of Mars. Several of the interior channels of Morava emanate from a localized region of terrain that is caving in, also called “subsidence.”

This region, comprised of jumbled blocks of flat-topped hills, is known as chaotic terrain. These channels, which emerge from the chaotic region, are separated by elongated hills that coalesce into a single channel before disappearing into the Margaritifer Chaos to the north. Chaotic terrains are thought to be the regions where ground water erupted catastrophically onto the surface, forming highly erosive flows that carved the outflow channels. The hills just downstream of the chaotic source region were shaped into streamlined islands by the erosive flows, forming blunt rounded ends in the upstream direction and tapering towards the north in the downstream direction.

Although windblown sediments now cover the original flood-carved channel floor in a sea of dunes, a 1.5 kilometer diameter impact crater provides a window into the sediment on the channel floor. The crater exposes several layers along its upper walls including a distinct bouldery layer just below the mantle of windblown sediments. These boulders may have originated from the eruption site and were transported and emplaced on the channel floor by high energy floods. Alternatively, these bouldery layers may be lava that subsequently flowed across the flood scarred channel floors.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA19116: Seeing Beneath the Surface in Morava Valles.

Tuesday, December 9, 2014

Gale Crater Lake

This illustration depicts a lake of water partially filling Mars' Gale Crater, receiving runoff from snow melting on the crater's northern rim. Evidence of ancient streams, deltas and lakes that NASA's Curiosity Mars rover mission has found in the patterns of sedimentary deposits in Gale Crater suggests the crater held a lake such as this more than three billion years ago, filling and drying in multiple cycles over tens of millions of years.

Gale Crater is 96 miles (154 kilometers) in diameter. This view is looking toward the southeast. The land surface in this illustration is the area's modern shape. Three billion years ago, the rim would have been higher and less eroded. A large layered mountain, Mount Sharp, now stands in the middle of Gale Crater. Accumulation of sediments in lakes, deltas, streams and wind-blown deposits is proposed to have formed the layers making up the lower portion of the mountain. When the crater first held a lake, it might have had central peak, much smaller than Mount Sharp, formed as a rebound from the impact that excavated the crater. Such a peak might have appeared as an island in the lake.

Illustration credit: NASA/JPL-Caltech

Note: For more information, see:
* PIA19067: Curiosity Mars Rover's Route from Landing to Base of Mount Sharp
* PIA19068: Inclined Martian Sandstone Beds Near 'Kimberley'
* PIA19069: Bedding Pattern Interpreted as Martian Delta Deposition
* PIA19070: Sets of Beds Inclined Toward Mount Sharp
* PIA19071: How a Delta Forms Where River Meets Lake
* PIA19072: Sol 696 (July 22, 2014), Left
* PIA19073: Multiple Deltas Built Out Over Time
* PIA19074: Sedimentary Signs of a Martian Lakebed
* PIA19075: Thin-Laminated Rock in 'Pahrump Hills' Outcrop
* PIA19076: Cross-Bedding at 'Whale Rock'
* PIA19077: Crystals May Have Formed in Drying Martian Lake
* PIA19078: Sediment Accumulation in Dry and Wet Periods
* PIA19079: Sedimentation and Erosion in Gale Crater, Mars
* PIA19081: Martian Rock's Evidence of Lake Currents
* NASA's Curiosity Rover Finds Clues to How Water Helped Shape Martian Landscape
* Mars Mountain was All Wet

Monday, December 8, 2014

Enigmatic Feature in Athabasca Lava Flows

What is this enigmatic landform?

The circular feature is nearly 2 kilometers (1.2 miles) wide. It looks like a circular island surrounded by a "sea" of smooth-looking lava flows. The Athabasca region contains some of the youngest lava flows on Mars. Therefore, it is highly possible that volcanism played a role in creating this feature.

Perhaps lava has intruded underneath this mound and pushed it up from beneath. It looks as if material is missing from the mound, so it is also possible that there was a significant amount of ice in the mound that was driven out by the heat of the lava. There are an array of features like this in the region that continue to puzzle scientists.

We hope that close inspection of this HiRISE image, and others around it, will provide some clues regarding its formation.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18932: An Enigmatic Feature in Athabasca Lava Flows.

Sunday, December 7, 2014

Clays Along the Coprates Chasma Plateau

This image shows exposures of deposits along the plateau just to the south of Coprates Chasma.

Whereas Coprates Chasma and many of the other chasmata of Valles Marineris contain kilometer-thick light-toned mounds made up of sulfates, several of the deposits along the plateau have signatures of clays. This indicates that water was here for extensive periods of time to cause the plains to weather and alter into clays.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18933: Clays along the Coprates Chasma Plateau.

Saturday, December 6, 2014

Dunes and Wind Streaks in Arabia Terra

Arabia Terra is one of the more dusty regions on Mars, where ever-falling red dust covers the surface allowing only minor variations in color and tone. One exception is when wind-driven, dark-toned sand moves across the surface ejecting the bright dust into the atmosphere to reveal the dust-free surface below.

This HiRISE image shows sand dunes with surrounding larger tear drop-shaped light streaks pointing west (or, to the left). This orientation, along with the morphology of the local dunes, indicates winds from the east have stripped sand particles off the dunes and carried them downwind to form these light streaks. More importantly, active sand has a role in the slow erosion of the rocks here and the overall landscape evolution of the region.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18931: Dunes and Wind Streaks in Arabia Terra.

Friday, December 5, 2014

Braided TARs in Syrtis Major

Transverse aeolian ridges (TARs) are commonly found throughout the Martian tropics, including rocky regions such as Syrtis Major that are largely devoid of dust.

These bright wind-blown ripples most often occur in simple sets of ridges with regular size and spacing. Typical TARs stand a few meters tall and have a wavelength (that is to say, separation) of 30 to 60 meters. HiRISE has not detected any changes among the TARs today, suggesting that they are inactive.

In this scene, we see TARs with a highly unusual morphology. Instead of single ridges, we see sets of small ridges that are separated by about 50 meters. The smaller ripples are spaced only 5 to 8 meters apart. Between the smaller ripples are even smaller striations that are perpendicular to the ridge crests with regular spacings of less than 2 meters.

This image raises a number of puzzling questions. Why are the ripples organized into two distinct wavelengths? Did the different wavelengths result from different processes or from different conditions? When did these wavelength-specific conditions or processes take place? Did they occur together, or did they alternate, or did one take place after the other? Were the processes depositional or erosional, or both?

The complexity of Martian TARs makes us think twice about any single explanation for their origin.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18930: Braided TARs in Syrtis Major.

Thursday, December 4, 2014

False Color Arsia Mons

This false color image shows part of the summit caldera of Arsia Mons. The mottled bluish tones are from clouds.

Orbit Number: 56650 Latitude: -9.51318 Longitude: 239.933 Instrument: VIS Captured: 2014-09-21 07:27

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

Wednesday, December 3, 2014

False Color Noctis Labyrinthus

This false color image covers part of Noctis Labyrinthus. The bluish tone in the lower elevation depressions may indicate atmospheric haze.

Orbit Number: 56612 Latitude: -5.85669 Longitude: 255.491 Instrument: VIS Captured: 2014-09-18 04:23

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