Monday, April 30, 2012

Sedimentary Layers in West Candor Chasma

West Candor Chasma in central Valles Marineris contains some of the thickest of the fine-grained layered deposits on Mars.

We can't see the grain sizes with HiRISE, but as the material erodes in the wind it disappears--apparently carried away by the wind--so the grains must be small. The layers may have been deposited from windblown materials, fall of volcanic sediments, or carried in by water, or all of the above.

Subsequently the layers may have been altered by groundwater, producing hydrated minerals such as sulfates. The enhanced colors in the sub image are related to the minerals or to overlying dust or sand. The dark blue sharp-crested ridges are sand dunes.

Photo credit: NASA/JPL/University of Arizona

Sunday, April 29, 2012

Tharsis Montes and Olympus Mons

Shaded relief image of Tharsis Montes and Olympus Mons derived from Mars Orbiter Altimeter data which flew on board NASA's Mars Global Surveyor. New data (see M. Beuthe et al., 2012) suggest that Tharsis Montes formed one by one, starting with Arsia Mons, possibly by the movement of a single mantle plume moving under the surface.

Photo credit: NASA; text credit: ESA

Note: For more information, see Mars Express Explores the Roots of Martian Volcanoes.

Saturday, April 28, 2012

Olympus Mons Topographical Map

Olympus Mons color-coded according to height from white (highest) to blue (lowest), based on images captured by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express. New data (see M. Beuthe et al., 2012) find that Olympus Mons is built on a rigid lithosphere whereas the nearby Tharsis Montes partially sank into a less rigid lithosphere, suggesting that there were large spatial variations in the heat flux from the mantle at the time of their formation.

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

Note: For more information, see Mars Express Explores the Roots of Martian Volcanoes.

Friday, April 27, 2012

Terrain Near the MSL Landing Site

This image is of a region slightly to the southwest of where the MSL rover, called Curiosity, will land in August 2012.

It shows three distinct terrains: (a) older plains, (b) an overlying unit with a distinct margin, and (c) recent sand dunes. The dunes indicate that the strongest winds tend to blow from the southwest toward the northeast and, like many dune fields on Mars, are probably moving slowly.

The second unit has a margin that, at low resolution, is similar to a lava flow. It also has a hard surface that retains impact craters better than the older plains beneath it.

At full HiRISE resolution it is evident that this deposit is not lava. It has thin layers and a dense network of fractures across its surface. The tops of some lava flows and lava lakes are also fractured. However, HiRISE has confirmed that the size and other characteristics of lava fractures are quite different from the ones visible here. Hence, this is some kind of sedimentary deposit, possibly consisting of largely of hardened mud.

It is likely that Curiosity will have an opportunity to investigate terrain like this soon after landing as it drives to the layered mound to the south.

Photo credit: NASA/JPL/University of Arizona

Monday, April 23, 2012

Active Dune Gullies in Kaiser Crater

Gullies remain an interesting feature to study on Mars, especially because we are still learning about their formation and what processes still act on them.

In this observation, we see large gullies on a huge, barchan dune. We've observed these gullies before, seeing that they appear to be active at different times. When we say "active," we mean that we can see changes in their appearance between different HiRISE images of the same area.

The major objective of this and similar images is to better understand the mechanism for these changes. A specific hypothesis the HiRISE team is investigating is that the changes we see are associated with frost deposits. The frost may be thick and heavy enough to cause parts of the sand dune to collapse, especially if it is "lubricated" by a layer of gas at the base of the frost layer. The gas would form at the bottom of the frost if sunlight passes through the frost and heats the underlying dark sand, working like a greenhouse.

Photo credit: NASA/JPL/University of Arizona

Sunday, April 22, 2012

Disappearing Boulder Tracks

This image was taken in February 2012, in order to compare against image ESP_017985_1985, which was acquired in May 2010. These two images are separated by approximately one Mars year.

The original image showed a prominent series of dark markings that are the tracks left by boulders as they rolled and bounced down the slope. As they do this, they set off miniature dust avalanches. The bright, fine dust slides away, leaving a darker, larger grained dust underneath.

This follow-up image shows that the smaller dark tracks are gone, and the larger ones have faded considerably. This is most likely due to the fine bright dust that is transported in the atmosphere falling down and re-covering the dark markings.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in southeastern "peninsula" of far northwestern Terra Cimmeria that borders northeastern Isidis Planitia.

Saturday, April 21, 2012

Late Springtime Defrosting of Northern Dunes

This observation shows dunes in the Martian north polar sand sea (commonly referred to as the "north polar erg") in the process of defrosting.

Every winter, dunes and other surfaces at these northern latitudes are coated with several tens of centimeters of carbon dioxide frost and ice, plus a minor amount of water frost. Details of this process are particularly visible this subimage. The white material is fine grained frost.

The dark, splotchy tones on the dunes may be deposits of particulates deposited from carbon dioxide "geysers" or relatively thick deposits of carbon dioxide ice. The more brownish colors represent defrosted areas. Polygonal patterns on the surface of the dunes are probably cracks in overlying carbon dioxide ice.

Landslides on the dunes' lee slopes are apparent, with a morphology consistent with fluidization from carbon dioxide frost. This and other areas of the north polar region are being investigated by HiRISE to compare to changes in past years.

Photo credit: NASA/JPL/University of Arizona

Friday, April 20, 2012

Landslides in a Terra Cimmeria Crater

The many large landslides inside Valles Marineris are well known, but there are also landslides elsewhere on Mars.

The southwest slope of this crater has at least three landslide lobes. What caused the landslides? They might have formed in the final stage of crater formation, but there are fewer subsequent craters on the lobes than elsewhere on the crater floor, so the landsliding occurred long after the crater's creation.

Perhaps the landslides were triggered by Marsquakes, either due to impact events or to faulting in the crust. Landslides are greatly facilitated by the presence of groundwater, which could have been present at the time these landslides happened, many millions of years ago.

Photo credit: NASA/JPL/University of Arizona

Note: This location is in Terra Cimmeria, to the southeast of Martz Crater.

Monday, April 16, 2012

A Volcanic Pit Chain and Dust Avalanches

This observation shows a volcanic pit chain in Amazonis Planitia.

Associated with two of the pits are meandering channels that splay into distributary patterns to the north. This suggests that the pits are eruptive centers, with the channels carved by lava.

A close-up image shows the eastern wall of the westernmost pit. The fluid-like streaks are the products of dust avalanches, with the dark color resulting from a thin coating of dust that has been removed from the surface.

The upper wall of the pit shows at least four distinct layers, each representing a sequence of one or more lava flows. A hazy, blueish haze bounds the outer circumference of the pit, perhaps resulting from suspended dust. The plains near the pit appear heavily muted, indicating a thick dust cover.

Photo credit: NASA/JPL/University of Arizona

Sunday, April 15, 2012

Terraces or Strata on a Crater Slope

This observation shows an interesting layered rock outcrop in the southeast Hellas Region. One of the scientific goals is to look for bedding features that might give clues to what deposited the material: subaerial, subaqueous or polar-ice-like?

Structural features cut through the layered material and strata at this location. Could these features be faults or dikes? Additional images of this region may help us find out.

Photo credit: NASA/JPL/University of Arizona

Saturday, April 14, 2012

Eroded Terrain Near Volcanic Fissures

This observation was taken to investigate the topography near the source of fluids from the Cerberus Fossae fractures in the Elysium Planitia region of Mars.

There are distinct channels carved into the terrain here, presumably by floods of water. However, the terrain is coated with lava, and this situation--where flood-eroded channels are completely coated with lava--is seen in many parts of Mars.

This leads some researchers to suggest that the channels were actually carved by the flowing lava, and that there was no flood of water. Images like these are helping to test these ideas.

This is a stereo pair with ESP_026158_1945.

Photo credit: NASA/JPL/University of Arizona

Friday, April 13, 2012

Layered Sediments in Danielson Crater

This crater is named for G. Edward Danielson, Jr. (1939–2005), who was instrumental in the development of a series of Mars cameras, from Mariner 4 launched in 1964 to the Mars Global Surveyor launched in 1996.

These layered sediments are of great interest because they are very regular in thicknesses, suggesting some sort of periodic process such as climate change associated with Mars orbital variations.

Photo credit: NASA/JPL/University of Arizona

Wednesday, April 11, 2012

Tractus Catena

Tractus Catena is shown here in a computer-generated perspective view. The image was created using data obtained from the High-Resolution Stereo Camera (HRSC) on ESA’s Mars Express spacecraft. The pits seen in the background show hints of layered bedrock in the upper walls of each depression.

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

Monday, April 9, 2012

20 Kilometer Tall Dust Devil in Amazonis Planitia

A dust devil the size of a terrestrial tornado towers above the Martian surface in this late springtime afternoon image of Amazonis Planitia.

Also captured by the Context Camera on MRO, the length of the shadow indicates that the dust plume reached a height of 20 kilometers (12 miles) above the surface! Despite its gargantuan height, the plume is only 70 meters (70 yards) in diameter, giving it a snake-like appearance that is twisted by high altitude winds, similar to another dust devil spotted recently in this region.

Typical tornadoes on Earth are less than 10 miles tall, while dust devils on our planet seldom reach more than a few hundred yards in height. So, why do we classify this plume as a monster dust devil and not a Martian tornado? Dust devils differ from tornadoes in their energy sources. Dust devils are driven by the heat of the surface, absorbed from sunlight and re-radiated to warm the atmosphere. The warm air rises and spins as it contracts, much as a figure skater spins faster as she draws her arms to her sides.

Tornadoes have an additional energy source: the heat given off as water vapor condenses into liquid rain. The condensing water vapor produces the visible part of a tornado, called the condensation funnel, which is made up of water droplets. On Mars, there is too little water vapor in the atmosphere to contribute significantly to atmospheric convection on local scales. The cloud that we see in this image is produced by dust particles, not raindrops. The astounding heights of Martian dust devils are made possible because mass of an atmospheric column on Mars is less than 1 percent than that of a column on Earth. Transfer of heat from the surface into this less dense atmosphere can produce more vigorous convection, which will penetrate higher into the Martian atmosphere than its counterparts do on Earth.

Now, what would happen if you were caught in its path? Because the density of Mars' atmosphere is so low, even a high velocity dust devil is unlikely to knock you over. However, you might be blasted by any sand or dust particles carried along by the dust devil, which might scratch the visor of your space suit quickly if you were caught outside by this monster!

This vortex left behind a bright track as its winds disturbed the dust-covered surface, tracing the path of the dust devil from the northwest towards the southeast. A dust "skirt" twice as wide as the plume itself is seen near the base of the dust devil, but the bright track is the size of the plume and not the skirt. Dozens of smaller dust devils were also spotted in the same Context Camera scene, steadily vacuuming the surface and pumping dust up into the Martian atmosphere.

JPL has produced two excellent animations of this dust devil in action.
Clip 1
Clip 2

Photo credit: NASA/JPL/University of Arizona

Note: For more information, see 12-Mile-High Martian Dust Devil Caught In Act.

Sunday, April 8, 2012

Layers in a Crater Wall in Noachis Terra

This image is of the rim of a crater. The Sun is low in the sky (only 15 degrees above the horizon) and shining full on this crater wall (you can see that the area beyond the rim has got long shadows).

The Sun is beautifully illuminating a series of layers exposed in the crater wall which have a variety of different colors.

Note: the subimage is non map-projected, so approximate North is down.

Photo credit: NASA/JPL/University of Arizona

Note: This crater is located in Noachis Terra to the northwest of Argyre Planitia. The closest named crater is Tábor, which is a very short distance to the northwest.

Saturday, April 7, 2012

Sedimentary Deposits on the Floor of Ritchey Crater

Ritchey Crater exposes some of the most colorful rock outcrops on Mars in its central peak.

This image reveals comparable diversity in some of the layered sediments and jumbled deposits (megabreccia) on the crater floor. In general the blues and greens indicate unaltered minerals like olivine and pyroxene whereas the warmer colors indicate altered minerals such as clays.

Photo credit: NASA/JPL/University of Arizona

Friday, April 6, 2012

Elephantine Lava Flow in Elysium Planitia

This observation highlights terrain that looks like an elephant. This is a good example of the phenomena "pareidolia," where we see things (such as animals) that aren't really there.

Actually, this image covers the margin of a lava flow in Elysium Planitia, the youngest flood-lava province on Mars. Flood lavas cover extensive areas, and were once thought to be emplaced extremely rapidly, like a flood of water.

Most lava floods on Earth are emplaced over years to decades, and this is probably true for much of the lava on Mars as well. An elephant can walk away from the slowly advancing flow front. However, there is also evidence for much more rapidly flowing lava on Mars, a true flood of lava. In this instance, maybe this elephant couldn't run away fast enough.

Note: the subimage is not map-projected, so approximate North is down.

Photo credit: NASA/JPL/University of Arizona

Note: This site is located in Phlegra Dorsa; the closest named impact crater is Lockyer, which is some distance off to the west.

Monday, April 2, 2012

Cratered Dune Forms in Melas Chasma

One of the scientific goals for taking this observation is to create a stereo pair with another HiRISE image. From stereo pairs, which are pictures of the same area but at different angles, HiRISE creates 3D or anaglyph pictures.

Known since at least 2003, this is a wonderful case of aeolian sandstone that (a) preserves its original sand dune bedform shapes and (b) lies unconformably over a previously-eroded surface of layered sedimentary rock.

Photo credit: NASA/JPL/University of Arizona

Note: This site is located on the southern wall of Melas Chasma.

Sunday, April 1, 2012

Lava Lamp Terrain on the Floor of Hellas Basin

Some of the weirdest and least-understood landscapes on Mars are on the floor of the deep Hellas impact basin. This image was acquired in northwest Hellas where depths are more than 6 kilometers below the reference (or roughly the average) altitude for Mars.

There are what look like impact craters but are elongated, as if stretched in a viscous manner (like in a lava lamp). Some of the flowing landforms are similar to those elsewhere in the middle latitudes of Mars, where the Shallow Radar (SHARAD) experiment on MRO has detected ice, but no ice detection has been reported here.

The floor of Hellas is relatively poorly mapped because it is often obscured by dust and haze in the atmosphere.

Photo credit: NASA/JPL/University of Arizona