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

Tuesday, December 2, 2014

False Color Claritas Fossae

This false color image shows part of Claritas Fossae.

Orbit Number: 56562 Latitude: -42.1269 Longitude: 263.184 Instrument: VIS Captured: 2014-09-14 01:23

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

Saturday, November 29, 2014

False Color Tithonium and Ius Chasmata

This false color image of the region including both Tithonium and Ius Chasmata includes a bluish region in both canyons. This may indicate an atmospheric haze. The potential haze appears to be more widespread in Ius Chasma.

Orbit Number: 56524 Latitude: -5.5587 Longitude: 273.654 Instrument: VIS Captured: 2014-09-10 22:30

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

Friday, November 28, 2014

False Color Ascraeus Mons

Today's VIS image is a false color image of part of the northern flank of Ascreaus Mons. The bluish section at the top of the image may indicate an atmospheric haze.

Orbit Number: 56512 Latitude: 13.2761 Longitude: 257.162 Instrument: VIS Captured: 2014-09-09 22:53

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

Thursday, November 20, 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

Wednesday, November 19, 2014

Spring in Inca City V

A significant event has occurred in Inca City. The layer of seasonal ice has started to develop long cracks. This is visible in the orange-colored band adjacent to the araneiforms. Fans of dust are emerging from long linear cracks. The cracks form when large plates of ice have no easily ruptured weak spots to release the pressure from gas building up underneath, so the ice simply cracks.

There are also more fans on the ridge at the top of the image, and more have appeared in between the araneiforms. We do not have any analogous processes occurring naturally on Earth: this is truly Martian.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18896: Spring in Inca City V.

Tuesday, November 18, 2014

Spring in Inca City IV

At certain times in spring, fans take on a gray or blue appearance. This is the time in Inca City when this phenomenon happens.

On the ridge at the top of the image fans have lengthened and now look more gray than the blotches on the araneiforms. At the bottom of the image they are distinctly blue in color.

Two theories have been suggested: perhaps fine particles sink into the seasonal layer of ice so they no longer appear dark. Or, maybe the gas that is released from under the ice condenses and falls to the surface as a bright fresh layer of frost. It is quite likely that both of these theories are correct.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18895: Spring in Inca City IV.

Monday, November 17, 2014

Spring in Inca City III

In Inca City another week has passed, and there are a few more fans on the ridge. We are studying the sequence of spring activity with the help of citizen scientists at the Planetfour website, sponsored by Zooniverse.

Citizens of planet Earth log on and identify and measure fans and blotches in the South polar region of Mars imaged by HiRISE. With their help we can study the polar weather by looking at how the fan directions change through the spring.

We see how the number of fans and blotches depends on the thickness of the ice layer and how high the sun is in the sky. If you would like to be a part of this endeavor join us at

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18894: Spring in Inca City III.