Terby Crater, a 170-km-wide (100-mile-wide) crater located on the northern edge of the vast Hellas Planitia basin in Mars’ southern hemisphere, is edged by variable-toned layers of sedimentary rock – possibly laid down over millennia of submersion beneath standing water. This image (false-color) from the HiRISE camera aboard the Mars Reconnaissance Orbiter shows a portion of Terby’s northern wall with what clearly looks like liquid-formed gullies slicing through the rock layers, branching from the upper levels into a main channel that flows downward, depositing a fan of material at the wall’s base.
But, looks can be deceiving…
Terby Crater. Credit: NASA/JPL/University of Arizona
Dry processes – especially on Mars, where large regions have been bone-dry for many millions of years – can often create the same effects on the landscape as those caused by running water. Windblown Martian sand and repetitive dry landslides can etch rock in much the same way as liquid water, given enough time. But the feature seen above in Terby seem to planetary scientists to be most likely the result of liquid erosion… especially considering that the sedimentary layers themselves seem to contain clay materials, which only form in the presence of liquid water. Is it possible that some water existed beneath Mars’ surface long after the planet’s surface dried out? Or that it’s still there? Only future exploration will tell for sure.
“While formation by liquid water is one of the proposed mechanisms for gully formation on Mars, there are others, such as gravity-driven mass-wasting (like a landslide) that don’t require the presence of liquid water. This is still an open question that scientists are actively pursuing.”
– Nicole Baugh, HiRISE Targeting Specialist
Terby Crater was once on the short list of potential landing sites for the new Mars Science Laboratory (aka Curiosity) rover but has since been removed from consideration. Still, it may one day be visited by a future robotic mission and have its gullies further explored from ground level.
Another great shot by the HiRISE camera on the Mars Reconnaissance Orbiter: this one of the Opportunity rover sitting on the edge of Santa Maria Crater. The High Resolution Imaging Science Experiment took this image on March 1, 2011, and also visible are the tracks in the Martian soil that Oppy created as she made her way to the crater.
“Opportunity has been studying this relatively fresh 90-meter diameter crater to better understand how crater excavation occurred during the impact and how it has been modified by weathering and erosion since,” said Matt Golombeck, a research geologist at the Jet Propulsion Laboratory, and part of the rover team. “Note the surrounding bright blocks and rays of ejecta.”
You can see a non-annotated image here. March 1 on Earth is the 2,524th Martian day, or sol, of Opportunity’s work on Mars.
By the way, MRO celebrates its 5th anniversary of being in orbit of Mars on March 10. Wow, 5 years already? But its been 5 years of great images and discoveries, with wishes from all of us for many more!
Mars, it is a-changin’, and more than scientists expected. Several series of before-and-after images taken by the HiRISE camera on the Mars Reconnaissance Orbiter the past two years show sand dunes in Mars northern hemisphere changing – both gradually and suddenly. A team of researchers analyzing the images say that the changes have been caused mostly by sand and ice cascading down the slipfaces of the dunes. But, also, there could be “alien” processes that we don’t see occurring on Earth.
“The numbers and magnitude of the changes have been really surprising,” said HiRISE Deputy Principal Investigator Candice Hansen.
The white arrows point to a location on the brink of this dune at 84°N, 233°E that had no alcove in the first year of HiRISE operation (MY29) and experienced sublimation activity (middle), which resulted in the new alcove and fan (with total length of 120 m) in MY30. The layer of new material forming the apron is very thin; the original ripples have not been completely buried. Image courtesy Science/AAAS.
In the past, Mars was thought to be a dead world, frozen in time with not many changes taking place on its surface. But since the arrival of high-resolution cameras orbiting the Red Planet – first on the Mars Global Surveyor, and now on MRO and ESA’s Mars Express – that notion has fallen by the wayside. Avalanches, new gullies and now shifting sand dunes are appearing regularly on images from Mars.
Even with the known winds on Mars, scientists had considered the dunes to be fairly static, shaped long ago when winds on the planet’s surface were thought to be much stronger than they are today.
Hansen and her colleagues’ new paper that is published in this week’s edition of the journal Science identifies the seasonal changes from a layer of frozen carbon dioxide – a.k.a or dry ice – which covers the region in winter and sublimates away in the spring, along with stronger-than-expected gusts of wind as initiating sand transport on the northern dunes of Mars.
Three images of the same location taken at different times show seasonal activity causing sand avalanches and ripple changes on a Martian dune. Credit: NASA/JPL/The University of Arizona.
“This gas flow destabilizes the sand on Mars’ sand dunes, causing sand avalanches and creating new alcoves, gullies and sand aprons on Martian dunes,” Hansen said. “The level of erosion in just one Mars year was really astonishing. In some places hundreds of cubic yards of sand have avalanched down the face of the dunes.”
Recently, scientists have seen how the scars of past sand avalanches could be partially erased in just one Mars year. Models of Mars’ atmosphere do not predict wind speeds adequate to lift sand grains, and data from Mars landers such as Phoenix show high winds are a rare occurrence.
“Perhaps polar weather is more conducive to high wind speeds,” Hansen said.
The dune margin in MY29 image PSP_008968_2650 at 84.7°N, 0.7°E is compared with MY30 ESP_017895_2650. Image courtesy of Science/AAAS
The researchers say changes were seen in about 40 percent of far-northern monitoring locations over the two-Mars-year period of the study.
Related research with HiRISE previously identified gully-cutting activity in smaller fields of sand dunes covered by seasonal carbon-dioxide ice in Mars’ southern hemisphere. A report four months ago showed that those changes coincided with the time of year when ice builds up.
A false-color image of dark sand dunes at high northern latitudes on Mars that are covered seasonally by a layer of condensed carbon dioxide (dry ice), shown in this image. When the sun rises in the spring the ice begins to sublimate. Gas flow from the bottom of the ice layer propels sand from the dunes out through cracks to the top of the ice and down the dune slipface. Image courtesy of NASA/JPL/University of Arizona
“The role of the carbon-dioxide ice is getting clearer,” said Serina Diniega of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., lead author of the earlier report and a co-author of the new report. “In the south, we saw before-and-after changes and connected the timing with the carbon-dioxide ice. In the north, we’re seeing more of the process of the seasonal changes and adding more evidence linking gully activity with the carbon dioxide.”
“Understanding how Mars is changing today is a key first step to understanding basic planetary processes and how Mars changes over time,” said HiRISE Principal Investigator Alfred McEwen, a co-author of both reports. “There’s lots of current activity in areas covered by seasonal carbon-dioxide frost, a process we don’t see on Earth. It’s important to understand the current effects of this unfamiliar process so we don’t falsely associate them with different conditions in the past.”
This unusual landscape on Mars can be found within a crater on the southern hemisphere of the Red Planet. But if you look on the actual location of this HiRISE image on the Google Map of Mars, below, you’ll see these spots are just spots among spots.
An area of heavy cratering on Mars. Credit: Google Maps (Mars)
Seasonal spots appear on dunes found on the floors of craters on Mars; most likely it is from carbon dioxide frost that is “defrosting” and later may sublimate away. At one time, these spots that seemingly come and go with the seasons were thought to be signs of life on Mars. The jury is still out on that line of thinking.
The folks from the HiRISE Camera on the Mars Reconnaissance Orbiter have put together a video with some groovin’ music of the latest images from the Red Planet, courtesy of HiRISE, the bestest camera in all of Marsdom. There’s an elliptical impact crater, giant gullies, sinuous ridges and a Swiss Cheese smiley face. No foolin’!
Richardson Crater Dunes, Partially Defrosted. Credit: NASA/JPL/University of Arizona
A new batch of images has been released by the HiRISE camera on the Mars Reconnaissaince Orbiter and –as usual — they are stunning. In the image above, there is a lot going on! Numerous dust devil tracks have left their criss-crossing marks on the dune field found in Richardson Crater. The dunes are covered by seasonal carbon dioxide frost, which has only partially defrosted, although the image was acquired late in Mars’ southern spring. There are channels carved into the ground and HiRISE scientists says the could have been created by blocks of carbon dioxide ice (dry ice) slide down the slope and sublimate (evaporate directly from solid to gas). Wouldn’t that be fun to be there and watch happen!
See more of the “coolest” and latest Mars images from HiRISE below:
The HiRISE camera on the Mars Reconnaissance Orbiter took an image of a thin channel, and a portion of it contains a naturally occurring bridge over the chasm. Kelly Kolb from the HiRISE team says it is probably a remnant of the original surface, the rest of which has collapsed downward. It isn’t likely there’s a opening underneath the formation, but if there were, it would look very similar to a rock bridge formation found in Jordan in the Wadi Rum, the Valley of the Moon. See an image below.
Kolb also said this is unlikely to be a channel formed by a running water, as there are no obvious source or deposit regions. The channel is probably a just a collapse feature.
And see the full HiRISE image of the thin channel, found in Mars northern hemisphere between some “knobs” called Tartarus Colles, below.
Any chance the Mars rockbridge could look like this one in Wadi Rum, Jordan -- also known as the Valley of the Moon?Small Winding Channel in Tartarus Colles. Credit: NASA/JPL/University of Arizona
Intriguing images of brand new, fresh gullies on Mars has most of us thinking of one thing: water. But at least for one type of Mars gully, carbon dioxide frost is the impetus behind fresh flows showing up on images from orbiting spacecraft.
“Gullies that look like this on Earth are caused by flowing water, but Mars is a different planet with its own mysteries,” said Serina Diniega, author of a new paper published in the journal Geology. “The timing we see points to carbon dioxide, and if the mechanism is linked to carbon-dioxide frost at these dune gullies, the same could be true for other gullies on Mars.”
Scientists have seen evidence of fresh gullies on Mars, beginning 2000 with images from the Mars Global Surveyor. Different mechanisms were proposed including water and carbon dioxide, as well as other forces.
On the HiRISE website, searching for “gullies” provides a bounty of images. Some fresh gullies are on sand dunes, commonly starting at a crest. Others are on rockier slopes, such as the inner walls of craters, sometimes starting partway down the slope.
Active Dune Gullies in Kaiser Crater (ESP_018186_1330) Active Dune Gullies in Kaiser Crater. Credit: NASA/JPL/University of Arizona
While a graduate student at the University of Arizona, Tucson, Diniega tracked changes in gullies on faces of sand dunes in seven locations on southern Mars. In looking at before-and-after images, in all cases, the gullies appeared after the known winter build-up of carbon-dioxide frost on the dunes. Before-and-after images that looked at periods in spring, summer and autumn showed no new activity.
Because new flows in these gullies apparently occured in winter, rather than at a time when any frozen water might be most likely to melt, Diniega and co-authors at the University of Arizona and Johns Hopkins University Applied Physics Laboratory believe they found evidence that carbon dioxide, rather than water, were responsible for the flows. Some carbon dioxide from the Martian atmosphere freezes on the ground during winter and sublimates back to gaseous form as spring approaches.
A series of images from HiRISE taken from 2008 to 2010 showing changes in a gully. Credit: NASA/JPL/University of Arizona
“One possibility is that a pile of carbon-dioxide frost accumulating on a dune gets thick enough to avalanche down and drag other material with it,” Diniega said. Other suggested mechanisms are that gas from sublimating frost could lubricate a flow of dry sand or erupt in puffs energetic enough to trigger slides.
The team focused their study on dune gullies that are shaped like rockier slope gullies, with an alcove at the top, a channel or multiple channels in the middle, and an apron at the bottom. The 18 dune gullies in which the researchers observed new activity range in size from about 50 meters or yards long to more than 3 kilometers (2 miles) long.
Thanks to the Mars Reconnaisance Orbiter and the on-board HiRISE camera, scientists are able to monitor Mars for changes taking place on the landscape. They do this by comparing older images with newer ones, and also by seeing “fresh” features — like this recent landslide in Zunil Crater. “The color and albedo patterns indicate that a landslide occurred here very recently–too recently to have been re-covered by dust,” writes Alfred McEwen, principal investigator of HiRISE, writing on the camera’s website. “Looking for changes such as this will help us to better understand active processes.” McEwen said the landslide could have been triggered by a Marsquake or a small impact event.”
See more recent landslides below:
This landslide was spotted by Stu Atkinson; boulders and debris are below a steep north polar boundary scarp. Credit: NASA/JPL/University of Arizona
Our ‘eagle-eyed’ pal Stuart Atkinson found this landslide on a steep scarp in the north polar region. It looks as though a lot of rock has fallen from the cliff, and discussion among other image artists on UnmannedSpaceflight.com indicated that the blue areas could easily be patches of ice deposited from the cliff face. You can see the original image at the HiRISE website.
Frosted Gullies in the Northern Summer. Credit: NASA/JPL/University of Arizona
This image is so amazing, in that from orbit, we are looking down the side of a crater wall, where gullies have formed. There are two schools of thought on these types of gullies: one, many scientists believe that these gullies have been carved by liquid water, and were carved recently, so this recent, present-day activity is of immense interest.
A second opinion is that accumulations of frost in the gully alcoves starts an avalanche of loose material that does not involve liquid water. The MRO scientists will continue to analyze many images like this in order to try and answer the broader question of whether liquid water is responsible for the the gullies, landslides and avalanches or not.
andslides along the Walls of Bahram Vallis. Credit: NASA/JPL/University of Arizona
This image of Bahram Vallis has large mounds of material at the base of the valley floor. These deposits of material have the characteristic shape of rotational landslides or slumps on Earth where material along the entire wall slumps down and piles debris at the base of the slope, “much like a person who slumps down the back of a chair,” writes Frank Chuang from the HiRISE team. “Right at the cliff edge at the top of the slope, the shape of the area where the valley wall gave way to a landslide is not straight, but rather curved or semi-circular. This is typical of large landslides where the failure area has an arcuate “crown” shape. The fact that landslides have occurred here indicates that the valley walls are not stable and the materials respond to Martian gravity with mass movements.”
Mars-o-philes rejoice! New images from Mars galore, including this “after” image of Mars’ northern hemisphere which reveals a new crater was created sometime between April 2004 and January 2010. Intriguingly, scientists believe exposed ice is visible in this new image from the HiRISE camera. This is just one of the latest release of hundreds of high-resolution HiRISE images, so go get your fill of Mars at the HiRISE site. But what about that ice?
The crater is at a latitude of 44 degrees North and is itself located on the ejecta of a larger crater. The image was acquired in early summer, when frost at this latitude is not expected. That’s why the HiRISE science team believes the bright blue material in this false-color color image is sub-surface ice that was exposed by the impact.
This ice is probably at the same depth and has a similar origin to that excavated by the Phoenix lander back in 2008. The area of exposed ice based on the HiRISE images is about 1-2 square meters (10-20 square feet.
An intriguing image, and a great example of the treasures available in this newest release of images from Mars.
