HiRISE Captioned Images 2019

[bystander]

Week of 21 January 2019

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Multi-Elevation Gullies (ESP_057450_1410) (HiClip)

Gullies probably formed along the bouldery layers in the upper slopes of this unnamed crater within the last few million years. Gullies eroded these crater slopes and transported sediment downslope forming debris aprons multiple times.

These older apron surfaces were cut by numerous fractures running perpendicular to the slope. Subsequent episodes of gully activity eroded through these fractures and deposited new aprons.

On the floor of the crater are ridges with bouldery layers. These ridges may mark the furthest extent of glaciers that predate much of the original gully activity. Bright flows continue to form in these gullies seasonally.

In the upper gully regions, long shadows cast by jagged outcrops allow scientists to determine the heights and depths of landforms by measuring the length of the shadows cast by the ridges onto the gully floor.

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Impact Near the South Pole (ESP_057152_0985) (HiClip)

This image shows a new impact crater that formed between July and September 2018. It’s notable because it occurred in the seasonal southern ice cap, and has apparently punched through it, creating a two-toned blast pattern.

The impact hit on the ice layer, and the tones of the blast pattern tell us the sequence. When an impactor hits the ground, there is a tremendous amount of force like an explosion. The larger, lighter-colored blast pattern could be the result of scouring by winds from the impact shockwave. The darker-colored inner blast pattern is because the impactor penetrated the thin ice layer, excavated the dark sand underneath, and threw it out in all directions on top of the layer.

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Cross-Section of a Complex Crater (ESP_058057_1465) (HiClip)

This image shows a cross-section of a complex crater in Terra Cimmeria.

Starting in the center, we see a series of peaks with exposed bedrock. These peaks formed during the impact event when material that was originally several kilometers below the surface was uplifted and exposed. The impact also melted the rocks. This eventually cooled, forming the pitted materials that coat the crater floor around the uplift.

The rim of the crater was unstable, and collapsed inwards to form terraces, and we see additional pitted materials between the terraces and the rim. Just outside the crater we can see dark-toned material that was excavated and thrown out after the impact.

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A First Look at Dunes (ESP_057903_1390) (HiClip)

This image shows us a cross-section of a dune field. Dune shape depends on several factors, including the amount of sand present and the local wind directions. This dune field displays several distinct dune morphologies.

We see both individual barchan-like dunes and more complex dune shapes. The dunes are arranged in a linear fashion at the northern extent of the field, first in areas with lots of sand, and then with relatively sand-free patches in between dune crests. HiRISE has observed dune activity in other similar fields, but this is our first image over this group of dunes.

A second image is needed to determine if these dunes are also evolving and moving.

Credit: NASA/JPL-Caltech/University of Arizona

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[bystander]

Week of 04 February 2019

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Exposing the Rock in Impact Craters (ESP_057866_1670) (HiClip)

In this complex crater (about 44-kilometers in diameter), we see bedrock in several locations from different depths in the crust. The central uplift exposes large fragments of green-toned bedrock that possibly originated from several kilometers beneath the surface.

To the south of the crater, we see more of this bedrock along with material that was excavated and thrown out after the impact. In craters of this size, the rim is unstable and collapses inwards forming terraces, which occasionally exposes more bedrock that would have originated from close to the surface than the rocks exposed within the uplift itself. Central uplifts have better exposures of bedrock, but in this example the terraces steal the show, displaying beautiful green- and light-toned bedrock at multiple locations.

This is a stereo pair with ESP_057932_1670.

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Layered History (ESP_057970_1645) (HiClip)

The geologic history of a planet is written in its layers. Erosion of the surface reveals several shades of light toned layers, likely sedimentary deposits.

The most recent geologic features are the narrow sand dunes snaking across the top of all the rock.

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A Dune Field near Nili Patera (ESP_057071_1890) (HiClip)

In this image many sand dunes are visible. They have an elongated crescent form and are called “barchan dunes.” They are formed by the continuous action of the wind, blowing in the same direction, giving this particular shape.

The orientation of these dunes tell us that the prevailing wind blows from the right to the left (east to west). The wind is continuously moving sand grains up the longer dune slope, towards the top. The small ripples on the slope are caused by this movement. When the sand grains arrive at the top, they fall down the steeper and shorter slope, which as a consequence, has no ripples. It is this gradual sand movement that causes the dunes to slowly move over time.

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Wind Flow (ESP_057930_1720) (HiClip)

The atmospheric pressure on Earth at sea level is about 1 bar. On Mars, the pressure is 6 to 10 millibars, or 1/100th that of our planet. But even in this atmosphere, wind still flows around obstacles.

In this image the ripples in the sand tell us which way the wind was moving and how it was diverted around these rock formations.

This is a stereo pair with ESP_057864_1720.

Credit: NASA/JPL-Caltech/University of Arizona

[bystander]

Week of 18 February 2019

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Following the Tracks (ESP_058427_1080) (HiClip)

Dust devils on Mars often create long, dark markings where they pull a thin coat of dust off the surface. This image shows a cluster of these tracks on the flat ground below the south polar layered deposits, but none on the layers themselves.

This tells us that either dust devils do not cross the layers, or they do not leave a track there. There are several possible reasons for this. For instance, the dust might be thick enough that the vortex of the dust devil doesn’t expose darker material from underneath the surface.

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Jumbled Blocks on the Floor of Melas Chasma (ESP_058527_1695) (HiClip)

This part of Melas Chasma has been the target for many previous HiRISE images due to its diversity of terrains and materials. This observation covers an area not previously imaged, revealing a chaotic jumble of bright layered sediments, perhaps resulting from large landslides.

In a closeup with enhanced colors, we can see an assortment of materials. Dark sand covers the low areas of the scene.

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Almost Like Water (ESP_057978_1875) (HiClip)

This image in Athabasca Valles shows lava flows originating from Elysium Mons to the northwest. A Context Camera image shows the lava flowed from the northwest to the southeast, diverting around obstacles as it settled. (The flow is outlined in blue with the flow direction shown in yellow, and the approximate location of the HiRISE image is represented by a white rectangle.)

The lava appears to have flowed smoothly around obstructions, almost like water, forming streamlined islands. In the southern part of this image, a branch of the flow diverts around a small crater, and eventually rejoins the main part of the flow. Irregular-shaped ring structures appear on the northern end and are related to the volcanic activity that formed the flows.

We also see a dense cluster of secondary craters that formed when material ejected from Corinto Crater (to the northwest) impacted the surface at high speed. At full-resolution, this terrain has the distinctive appearance of a field of numerous, small and closely-spaced craters.

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A Recent Impact Site in Noachis Terra (ESP_057984_1490) (HiClip)

This image shows a recent impact in Noachis Terra in the southern mid-latitudes of Mars. The impact occurred in dark-toned ejecta material from a degraded, 60-kilometer crater to the south.

Rather than a single impact crater, we see multiple impacts like a shotgun blast. This suggests that the impactor broke up in the atmosphere on entry. Although the atmosphere of Mars is thinner than Earth’s, it still has the capacity to break up small impactors, especially ones comprised of weaker materials, like a stony meteoroid versus a iron-nickel one.

Our image depicts 21 distinctive craters ranging in size from 1 to 7 meters in diameter. They are distributed over an area that spans about 305 meters. Most observed recent impacts expose darker-toned materials underlying bright dusty surfaces. However, this impact does the opposite, showing us lighter-toned materials that lie beneath a darker colored surface.

The impact was initially discovered in a 2016 Context Camera image, and was not seen in a 2009 picture. This implies that the impact may be only two years old, but certainly no more than nine years.

This is a stereo pair with ESP_049175_1490.

Credit: NASA/JPL-Caltech/University of Arizona

[bystander]

Week of 04 March 2019

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The Slow Charm of Brain Terrain (ESP_058008_2225)

You are staring at one of the unsolved mysteries on Mars. This surface texture of interconnected ridges and troughs, referred to as “brain terrain” is found throughout the mid-latitude regions of Mars. (This image is in Protonilus Mensae.)

This bizarrely textured terrain may be directly related to the water-ice that lies beneath the surface. One hypothesis is that when the buried water-ice sublimates (changes from a solid to a gas), it forms the troughs in the ice. The formation of these features might be an active process that is slowly occurring since HiRISE has yet to detect significant changes in these terrains.

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Gullies in Galle (ESP_058196_1280)

This image was taken of the hills that resulted from uplifted rocks due to an impact that formed the 230-kilometer diameter Galle Crater.

These hills form a segment of a circle known as a “peak ring” and this particular formation makes Galle Crater look like a “smiley face” from orbit.

Small gullies, visible in the center of this image, have formed on the flanks of these hills and they have eroded back into the bedrock. The crater itself is probably billions of years old, yet these gullies are likely only hundreds of thousands of years old and may even be active today.

The small channels in these gullies are easily erased by the wind over long time periods, so we know these gullies must have been active recently.

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Colorful Impact Ejecta in Ladon Valles (ESP_058565_1620)

This image covers the western portion of a well-preserved (recent) impact crater in Ladon Basin. Ladon is filled by diverse materials including chemically-altered sediments and unaltered lava, so the impact event ejected and deposited a wide range of elements.

This image is the first of a pair of images for stereo coverage, so check out the stereo anaglyph when completed.

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Colorful Mawrth Vallis (ESP_058749_2060)

Mawrth Vallis is a place on Mars that has fascinated scientists because of the clays and other hydrated minerals detected from orbit.

In this image, the enhanced black colors are most likely basaltic sands and rocks, while the green, yellow, and blue colors correspond to the different hydrated minerals.

This particular image was taken of a location in Mawrth Vallis that has a mineral called jarosite. Jarosite on Earth forms under wet, oxidizing, and acidic conditions. Another place on Mars where the Opportunity rover landed and explored also has jarosite.

This is a stereo pair with ESP_058182_2060.

Credit: NASA/JPL-Caltech/University of Arizona

[bystander]

Week of 18 March 2019

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Complex Gullies in a Crater (ESP_058399_1415) (HiClip)

Most gullies in the southern mid-latitudes are on south-facing slopes, which are the coldest and have the most frost in the winter. However, some occur on other slopes.

This image shows large gullies on both the pole- and equator-facing slopes. An important puzzle in Mars science is whether or not all of these gullies form in the same geologic eras and by the same processes.

If you have red/green glasses, be sure to check out the anaglyph of this crater, which shows rugged topography!

This is a stereo pair with ESP_057700_1415.

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Everything is (Well) Illuminated (ESP_058538_0960) (HiClip)

The south polar layered deposits are icy layers that have been deposited over millions of years, preserving a climate history of Mars. In this image the layers are well illuminated to accentuate the topography.

A prior image of this location was acquired with the layered slope facing away from the sun, placing the layers in shadow. (The top of the cutout image is at a higher elevation.)

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In the Gullies and Bedrock of Ius Chasma (ESP_058580_1720) (HiClip)

This image was acquired in Ius Chasma, a major section of the western portion of the giant Valles Marineris trough.

We see a portion of a steep slope with gullies extending downhill (towards bottom of image). Many of the gully floors are dark, and in some places that dark material extends onto the fan-shaped deposits of the gullies. These dark features are candidates for recurring slope lineae (RSL), which are seasonal features that grow incrementally. The relation between RSL and gullies is not clear: does the RSL activity carve the gullies, or do they simply follow the gully topography created by other processes?

Another closeup from this observation shows part of the floor of Ius Chasma, with layered bedrock draped by dunes.

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Bedrock in the Central Peaks of Hale Crater (ESP_058618_1445) (HiClip)

This long image is entirely over the extensive central peak complex of Hale Crater.

Of particular interest are bedrock outcrops and associated fine-grained sediments with different colors. This 153-kilometer diameter crater was named after American astronomer George Ellery Hale.

Credit: NASA/JPL-Caltech/University of Arizona

[bystander]

Week of 01 April 2019

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The Hills in Juventae Chasma (ESP_058566_1760) (HiClip)

This image captures some of the geologic diversity of Mars. There are hills of ancient terrains on the floor of Juventae Chasma, surrounded by younger sediments, including dark sand sheets and dunes that are likely active today.

The hills are heavily eroded by landslides, forming gullies in some places. Diverse colors represent unaltered volcanic minerals (blue and green) and altered minerals (brighter and reddish colors).

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Dramatic Changes over the South Polar Cap (ESP_058515_0955) (HiClip)

The south polar residual cap of carbon dioxide ice rapidly changes. This image was planned as an almost exact match to the illumination and viewing angles of a previous one we took in August 2009.

The pits have all expanded and merged, and we can just barely see the patterns in the 2009 image compared to this January 2019 picture. The 2009 image is also brighter and bluer, with more seasonal frost and/or less dust over the surface. These images were both taken in late southern summer, but our 2019 picture is slightly later in the Martian season by about two weeks.

This gap allowed for additional loss of frost that might make the surface darker, but there are also year-to-year changes. In particular, there was a near-global dust storm in the summer of 2018 and late southern spring on Mars, and extra deposits of dust would have warmed the surface and promoted even more disappearance of the frost.

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Clay-Rich Terrain in Eridania Basin (ESP_058610_1515) (HiClip)

HiRISE reveals small-scale shapes that often correlate with mineral units and provides information about stratigraphy (i.e., what’s on top and relative ages). This image was acquired for co-analysis with a spectrometer instrument also on our spacecraft called CRISM (Compact Reconnaissance Imaging Spectrometer for Mars). It shows polygonal units that match clay-rich areas. Plus, this region is colorful!

This location, in Eridania Basin, was the site of an ancient lake, so these clay-rich sediments may have been habitable.

While CRISM cannot acquire new data from their infrared channel due to lack of cooling, they have acquired much previous data that lacks HiRISE coverage.

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A Crater on the South Polar Layered Deposits (ESP_058600_0990) (HiClip)

This image is part of a campaign to image potential impact craters in the south polar layered deposits (ice cap). This feature looks like a strong candidate for an impact crater because it is very circular are still has a raised rim.

The sizes and densities of impact craters provide an estimate for the age of the landscape, which in turn provides a minimum age for the icy layers.

Credit: NASA/JPL-Caltech/University of Arizona

[bystander]

Week of 15 April 2019

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Impact-Induced Dust Avalanches (ESP_058514_2140) (HiClip)

HiRISE has been imaging new dark features discovered by MRO’s Context Camera, which are mostly new impact sites. In this scene we see what appears to be a new impact cluster and, extending downhill from the craters, new dark slope streaks.

These slope streaks are formed by dry dust avalanches. We’ve also seen large new dust avalanches associated with new impacts at previous locations.

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Landslides in Cerberus Fossae (ESP_058571_1965) (HiClip)

Cerberus Fossae is a steep-sided set of troughs cutting volcanic plains to the east of Elysium Mons. Steep slopes on Mars have active landslides (also called “mass wasting”), and here we see evidence for two types of activity.

First, the light bluish boulders on the slope appear to originate at a layer of bedrock (also light blue) near the top of the section. Second, the dark thin lines are recurring slope lineae, probably also due to mass wasting, but composed of finer-grained materials.

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Bedrock on the Floor of Kaiser Crater (ESP_058616_1330) (HiClip)

HiRISE has often imaged inside Kaiser Crater to monitor active sand dunes and gullies. Surrounding these dunes, we often find clean bedrock exposures, because the actively moving sand clears off the dust.

Kaiser Crater is 207 kilometers wide and was named after Frederik Kaiser, a Dutch astronomer (1808—1872).

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Abstract Art in Ius Chasma (ESP_058593_1710) (HiClip)

Sometimes Mars’ surface is just beautiful as seen through the eyes of HiRISE.

This is one example on the floor of Ius Chasma, part of Valles Marineris. The region has had a complex history of sediment deposition, deformation, erosion, and alteration.

Credit: NASA/JPL-Caltech/University of Arizona