High Resolution Imaging Science Experiment (HiRISE) Archives

May 15, 2013December 23, 2015 by Nancy Atkinson

Mars Gets Bombarded by 200 Small Asteroids and Comets Every Year

A relatively new cluster of impact craters on Mars as seen by the HiRISE camera on the Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/MSSS/Univ. of Arizona

One of the benefits of having a spacecraft in orbit around another planet for several years is the ability to make long-term observations and interpretations. The Mars Reconnaissance Orbiter has been orbiting Mars for over seven years now, and by studying before-and-after images from the High Resolution Imaging Science Experiment (HiRISE) camera, scientists have been able to estimate that the Red Planet gets womped by more than 200 small asteroids or bits of comets per year, forming craters at least 3.9 meters (12.8 feet) across.

“It’s exciting to find these new craters right after they form,” said Ingrid Daubar of the University of Arizona, Tucson, lead author of the paper published online this month by the journal Icarus. “It reminds you Mars is an active planet, and we can study processes that are happening today.”

New impact site on Mars formed between November 2005 and October 2010. Credit: NASA/JPL-Caltech/MSSS/Univ. of Arizona

Over the last decade, researchers have identified 248 new impact sites on parts of the Martian surface in the past decade from spacecraft images, determining when the craters appeared. The 200-per-year planetwide estimate is a calculation based on the number found in a systematic survey of a portion of the planet.

The orbiters took pictures of the fresh craters at sites where before-and-after images by other cameras helped figure out when the impacts occurred. This combination provided a new way to make direct measurements of the impact rate on Mars. This will lead to better age estimates of recent features on Mars.

Daubar and co-authors calculated a rate for how frequently new craters at least 3.9 meters in diameter are excavated. The rate is equivalent to an average of one each year on each area of the Martian surface roughly the size of the U.S. state of Texas. Earlier estimates pegged the cratering rate at three to 10 times more craters per year. They were based on studies of craters on the moon and the ages of lunar rocks collected during NASA’s Apollo missions in the late 1960s and early 1970s.

“Mars now has the best-known current rate of cratering in the solar system,” said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, a co-author on the paper.

Examples of craters listed in the paper 'The Current Martian Cratering Rate.' Credit: NASA/JPL/Univ. of Arizona. — Examples of craters listed in the paper ‘The Current Martian Cratering Rate.’ Credit: NASA/JPL/Univ. of Arizona.

These asteroids, or comet fragments, typically are no more than 3 to 6 feet (1 to 2 meters) in diameter. Space rocks too small to reach the ground on Earth cause craters on Mars because the Red Planet has a much thinner atmosphere.

For comparison, the meteor over Chelyabinsk, Russia, in February was about 10 times bigger than the objects that dug the fresh Martian craters.

HiRISE targeted places where dark spots had appeared during the time between images taken by the spacecraft’s Context Camera (CTX) or cameras on other orbiters. The new estimate of cratering rate is based on a portion of the 248 new craters detected. It comes from a systematic check of a dusty fraction of the planet with CTX since late 2006. The impacts disturb the dust, creating noticeable blast zones. In this part of the research, 44 fresh impact sites were identified.

Estimates of the rate at which new craters appear serve as scientists’ best yardstick for estimating the ages of exposed landscape surfaces on Mars and other worlds.

One of many fresh impact craters spotted by the UA-led HiRISE camera, orbiting the Red Planet on board NASA's Mars Reconnaissance Orbiter since 2006. (Photo: NASA/JPL-Caltech/MSSS/UA). — One of many fresh impact craters spotted by the UA-led HiRISE camera, orbiting the Red Planet on board NASA’s Mars Reconnaissance Orbiter since 2006. (Photo: NASA/JPL-Caltech/MSSS/UA).

See the abstract and other information here.
Source: JPL

April 10, 2013December 23, 2015 by Nancy Atkinson

Tell-tale Evidence of Bouncing Boulders on Mars

A closeup of an impact crater shows distinctive bright lines and spots on the steep slope, indicating bouncing boulders have fallen down the incline. Credit: NASA/JPL/University of Arizona.

What are the types of things that happen on Mars when we’re not looking? Some things we’ll never know, but scientists with the HiRISE camera on the Mars Reconnaissance Orbiter have seen evidence of bouncing boulders. They haven’t actually captured boulders in the act of rolling and bouncing down the steep slope of an impact crater (but they have captured avalanches while they were happening!)

Instead, they see distinctive bright lines and spots on the side of a crater, and these patterns weren’t there the last time HiRISE imaged this crater 5 years ago (2.6 Mars years ago), in March 2008.

“The discontinuous bright spots indicate bouncing, so we interpret these features as due to boulders bouncing and rolling down the slope,” said HiRISE principal investigator Alfred McEwen, writing on the HiRISE website.

Where did the boulders come from?

“Maybe they fell off of the steep upper cliffs of the crater, although we don’t see any new bright features there that point to the source,” McEwen said. “Maybe the rocks were ejecta from a new impact event somewhere nearby.”

The trails are quite bright, and McEwen said that perhaps the shallow subsurface soil here is generally brighter than the surface soil, just like part of Gusev Crater, as the Spirit rover found. McEwen added that the brightness can’t be from ice because this is a warm equator-facing slope seen in the summer.

Source: HiRISE

April 3, 2013December 23, 2015 by Nancy Atkinson

Watch Curiosity’s Parachute Flap in the Martian Breeze

This sequence of seven images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter shows wind-caused changes in the parachute of NASA's Mars Science Laboratory spacecraft as the chute lay on the Martian ground during months after its use in safe landing of the Curiosity rover. Image credit: NASA/JPL-Caltech/Univ. of Arizona.

How cool is this? An animation of seven images from the HiRISE camera on the Mars Reconnaissance Orbiter show a “flapping” of the parachute that allowed the Curiosity rover to descend safely through Mars atmosphere images. The chute, imaged as it lay on the ground following the rover’s safe landing, was blown about by the Martian breeze! The images were acquired by HiRISE between August 12, 2012 and January 13, 2013. The different images show distinct changes in the parachute, which is attached to the backshell that encompassed the rover during launch, flight and descent.

The HiRISE team explains the animation:

In the first four images there are only subtle changes, perhaps explained by differences in viewing and illumination geometry.

Sometime between September 8, 2012 and November 30, 2012, there was a major change in which the parachute extension to the southeast (lower right) was moved inward, so the parachute covers a smaller area. In the same time interval some of the dark ejecta around the backshell brightened, perhaps from deposition of airborne dust.

Another change happened between December 16, 2012 and January 13, 2013, when the parachute shifted a bit to the southeast. This type of motion may kick off dust and keep parachutes on the surface bright, to help explain why the parachute from Viking 1 (landed in 1976) remains detectable.

Here’s another version from UnmannedSpaceflight.com’s Doug Ellison:

The Mars Science Laboratory's parachute flaps in the wind on Mars. Images by the HiRISE camera on the Mars Reconnaissance Orbiter, animation by Doug Ellison. — The Mars Science Laboratory’s parachute flaps in the wind on Mars. Images by the HiRISE camera on the Mars Reconnaissance Orbiter, animation by Doug Ellison.

And here’s a look at how big the chute really is (note the people for scale):

MSL parachutte tested in a wind tunnel. Credit: JPL.

Source: HiRISE

February 12, 2013December 23, 2015 by Nancy Atkinson

10 Amazing 3-D Views from the Mars Reconnaissance Orbiter

The Dunes of 'Inca City.' Credit: NASA/JPL/University of Arizona.

These pictures require you to grab the 3-D glasses you have handy by your desk (if you don’t have a pair, here’s some great options for buying some) and get a “you-are-there” experience from the HiRISE camera on the Mars Reconnaissance Orbiter. Here, you can virtually tumble down crater walls, hover over steep cliffs, and see how layered bedrock appears from above.

Our lead image is of an area referred to as “Inca City,” the informal name given by Mariner 9 scientists in 1972 to a set of intersecting, rectilinear ridges, which some people thought looked like structures or streets. Even back then scientists thought they might be dunes, but that didn’t keep people from going off the deep end about this region. But the power of HiRISE has revealed these truly are dunes, and in this image you can see some of the seasonal processes as the region goes from winter to spring. As the carbon dioxide frost and ice on the dunes warms, small areas warm and sublimate (turn from solid to gas) faster, creating a speckled surface.

Enjoy more 3-D views below. All images link directly to the HiRISE site where you can see other versions and get more info about each image. See all the HiRISE anaglyphs that are available here.

Fresh 4-Kilometer Rayed Crater Northeast of Chimbote Crater. Credit: NASA/JPL/University of Arizona.

Cliff with Columnar Jointing. Credit: NASA/JPL/University of Arizona.

Central Uplift of a Large Impact Crater. Credit: NASA/JPL/University of Arizona.

Buttes and craters: Compositional Diversity in Northern Hellas Region. Credit: NASA/JPL/University of Arizona.

Well-Preserved 4-Kilometer impact Crater. Credit: NASA/JPL/University of Arizona.

Flow Boundary in Elysium Planitia. Credit: NASA/JPL/University of Arizona.

A fissure on Mars named Cerberus Fossae. Credit: NASA/JPL/University of Arizona.

Possible Gullies in Graben. Credit: NASA/JPL/University of Arizona.

Layered Bedrock on Crater Floor. Credit: NASA/JPL/University of Arizona.

January 16, 2013December 23, 2015 by Nancy Atkinson

Curiosity’s Rambling Tracks Visible from Mars Orbit

Tracks from the Curiosity rover were imaged by the HiRISE camera on the Mars Reconnaissance Orbiter on January 2, 2012. Credit: NASA/JPL/University of Arizona.

Look closely and see where the Curiosity rover has been roving about inside Gale Crater on Mars, from “Bradbury Landing” to its current location in “Yellowknife Bay.” This shot was taken by the HiRISE camera on board the Mars Reconnaissance Orbiter on January 2, 2013.

“This image shows the entire distance traveled from the landing site (dark smudge at left) to its location as of 2 January 2013 (the rover is bright feature at right),” wrote HiRISE principal investigator Alfred McEwen on the HiRISE website. “The tracks are not seen where the rover has recently driven over the lighter-toned surface, which may be more indurated [hardened] than the darker soil.”

You can compare this image to one taken on September 8, 2012 to see how much the rover has driven in Gale Crater:

Curiosity rover tracks seen from orbit by HiRISE on September 8, 2012. Credit: NASA/JPL/University of Arizona.

And here’s a map of Curiosity’s travels that NASA released yesterday:

This image maps the traverse of NASA's Mars rover Curiosity from "Bradbury Landing" to "Yellowknife Bay," with an inset documenting a change in the ground's thermal properties with arrival at a different type of terrain. Image credit: NASA/JPL-Caltech/Univ. of Arizona/CAB(CSIC-INTA)/FMI.

Mission scientists said at a briefing yesterday (January 15, 2013) that between Sol (Martian day) 120 and Sol 121 of the mission — which equates to Dec. 7 and Dec. 8, 2012 — Curiosity crossed over a terrain boundary into lighter-toned rocks that correspond to high thermal inertia values observed by NASA’s Mars Odyssey orbiter. The green dashed line marks the boundary between the terrain types.

The inset graphs the range in ground temperature recorded each day by the Rover Environmental Monitoring Station (REMS) on Curiosity. Note that the arrival onto the lighter-toned terrain corresponds with an abrupt shift in the range of daily ground temperatures to a consistently smaller spread in values. This independently signals the same transition seen from orbit, and marks the arrival at well-exposed, stratified bedrock.

Sol 124 (Dec. 11, 2012) marked the arrival into an area called “Yellowknife Bay,” where sulfate-filled veins and concretions were discovered, along with much finer-grained sediments providing evidence of past water interacting with the surface.

Here’s the Mars weather report provided by REMS for Sol 158 (January 15, 2013):

Daily Weather Report
Image credit: NASA/JPL-Caltech. — Daily Weather Report. Image credit: NASA/JPL-Caltech.

A video showing the new HiRISE image of Curiosity’s tracks:

August 17, 2012December 23, 2015 by Nancy Atkinson

Spectacular ‘Sideways Glance’ of Mt. Sharp in Gale Crater

Yep, you really want to click on this link to see the full color version of this great oblique view of Mt. Sharp (a.k.a. Aeolis Mons) in Gale Crater, taken by the HiRISE camera on the Mars Reconnaissance Orbiter. Or you can click here to see the full “raw” strip from the spacecraft.

“The viewing angle is 45 degrees, like looking out an airplane window,” wrote HiRISE Principal Investigator Alfred McEwen on the HiRISE website. McEwen noted that this color version doesn’t show the Curiosity rover or the hardware left over from the landing on Mars, but it does provide a great view of Gale Crater’s central mound.

So how “true” is the color in this image?

“It may be close, but not true,” Christian Schaller from the HiRISE team told Universe Today. Schaller pointed out the description (pdf) of color in HiRISE images from the HiRISE team:

It isn’t natural color, as seen by normal human eyes, because the IR, RED, and BG channels are displayed in red, green, and blue colors. For the Extras products, each color band is individually stretched to maximize contrast, so the colors are enhanced differently for each image based on the color and brightness of each scene. Scenes with dark shadows and bright sunlit slopes or with both bright and dark materials are stretched less, so the colors are less enhanced than is the case over bland scenes.

Jim Bell, the lead scientist for the Pancam color imaging system on the Mars Exploration Rovers, said he likes to use the term “approximate true color” because the MER panoramic camera images are estimates of what humans would see if they were on Mars. Other colleagues, Bell said, use “natural color.”

“We actually try to avoid the term ‘true color’ because nobody really knows precisely what the ‘truth’ is on Mars,” Bell told Universe Today in 2007 for an article about the art of extraterrestrial photography. In fact, Bell pointed out, on Mars, as well as Earth, color changes all the time: whether it’s cloudy or clear, the Sun is high or low, or if there are variations in how much dust is in the atmosphere. “Colors change from moment to moment. It’s a dynamic thing. We try not to draw the line that hard by saying ‘this is the truth!’”

For more great shots from HiRISE, check out their website.

Source: HiRISE

July 12, 2012December 23, 2015 by Nancy Atkinson

Latest from Mars: Massive Polar Ice Cliffs, Northern Dunes, Gullied Craters

Several gorgeous images are in this week’s update from the HiRISE camera on board the Mars Reconnaissance Orbiter. This lovely image shows the cliffs at the edges of huge ice sheet at the North Pole of Mars. These cliffs are about 800 meters (2,600 feet) high, and the ice sheet is several kilometers thick at its center. This is a great spot to look for ice avalanches that HiRISE has captured previously. The HiRISE team said that the slopes of these cliffs are almost vertical, plus dense networks of cracks cover the icy cliff faces making it easier for material to break free. The team regularly monitors sites like this to check for new blocks that have fallen. You can look for yourself to see if any avalanches have occurred since the last image was taken of this area, almost exactly one Martian year ago.

The HiRISE scientists monitor these regions to help in understand the climatic record stored in the ice sheet itself.

What else did HiRISE see this week?

These cool-looking dunes look reminiscent of Pac-Man, and they might even be moving across the surface of Mars! They are approximately 100 meters across and are traversing a bumpy, hard terrain, pushed across the surface by the winds on Mars. The HiRISE team will take more images of this dune field in subsequent passes to determine whether these dunes are really moving.

This image shows a gullied crater in the Southern mid-latitudes with light-toned deposits near the center of its floor, and two areas of collapsed terrain at the northern and southern edges of the crater floor.

For more information on each of these images, click on them to see the original page on the HiRISE website, or go to the HiRISE website to see all the wonderful images from Mars.

March 29, 2012March 16, 2016 by Nancy Atkinson

Did Water or Lava Carve the Outflow Channels on Mars?

Outflow channel in the Tharsis region on Mars. Credit: NASA/JPL/University of Arizona

Large features on Mars called outflow channels have been a point of contention among planetary scientists. “Most Mars scientists accept that outflow channels were carved by water, but alternate hypotheses persist, especially that lava carved the outflow channels,” said Alfred McEwen Principal Investigator of the HiRISE camera on the Mars Reconnaissance Orbiter. McEwen said that water is still the preferred mechanism and he doubts that all the channels could have been created by lava flows.

But in what could be seen as a type of compromise, he offered a new theory for the outflow channels, based on observations by HiRISE: the channels were originally carved by huge water flows on ancient Mars and later were partially filled in by lava.

“This sequence of events provides a better explanation,” McEwen said.

Large outflow channels can be 10 km or more in width and may be hundreds of kilometers long. From orbital images, they appear to be huge, dry river beds, carved by very large volumes of running water.

While these features are too large to have been caused by flooding from rainfall, other explanations have been offered. One model involves large amounts of water frozen as permafrost in the soil and when a major source of local heating occurred, such as volcanic activity, there was melting and catastrophic flooding.

However, other explanations don’t involve water at all, but suggest flowing lava created these channels.

Speaking at the 2012 Lunar and Planetary Science Conference last week, McEwen mentioned specifically one proponent of the lava hypothesis, David Leverington from Texas Tech University, who proposed last year that slippery, low-viscosity lavas created the channels. Leverington says the lava hypothesis offers a simpler explanation that fits well within a wider geological framework of Mars and compares well with similar channel-like features on the Moon and Venus.

“He makes some good points,” McEwen said, “and argues for a form of Occam’s Razor. But we have been searching extensively with HiRISE and finding things that satisfy Leverington’s challenges.”

McEwen said the abundant evidence of water carving the channels is too hard to dismiss. Several examples of outflow channels show deposits from water-based flooding that lava flow can’t explain; additionally, there is ample evidence of bedrock erosion by water on Mars.

McEwen also said crater dating areas of several outflow channels show that the channels themselves are older than the lava flow.

“In the Athabasca Valles channels, MRO data showed that lava completely filled the channels and even overflow in places,” he said. “The lava can actually make channels look young.”

Uzboi Valles offers the best counterexample to Leverington’s hypothesis, McEwen said. “No lava fills in this highlands channel, and the channel preserves local layered alluvial deposits and shorelines. So that means we cannot explain all outflows channels from lava erosion.”

McEwen and his team suggest that large floods may have occurred in the Hesperian to early Amazonian, ending about 1 to 1.5 billion years ago, carving the channels. Then, later came the lava flows that formed Mars’ broad plains and sand dunes that we now see – which also filled in some of the outflow channels.

But McEwen said the debate about these channels is good science. “Did water create these channels? That is a good question,” he said. “We shouldn’t just assume the answer is yes. But we propose water must have carved at least some of the channels, and that water outflow is the main mechanism. If you disagree with anything I’ve said, go to the HiRISE website’s “HiWish” page to suggest areas for further imaging of these features. I’ve been disappointed how few members of the science community have used this tool,” he said.

Clouds Get in the Way on Mars

Clouds give a fuzzy view of ice-topped dunes on Mars. Credit: NASA/JPL/University of Arizona

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The science team from the HiRISE camera on the Mars Reconnaissance Orbiter wanted to take another look at a region of icy sand dunes on Mars to look for seasonal changes as spring is now arriving on the Red Planet’s northern hemisphere. But the view was obstructed by clouds, creating this unusual hazy view.

“This happens occasionally. We’ve found that weather forecasting on Mars is just as challenging — if not more — than on Earth,” said HiRISE team member Candy Hansen, who I nabbed in the hallway during the Lunar and Planetary Science Conference today, to ask about this unique image. “The clouds are likely made of water ice crystals, and the dunes have a coating of CO₂ ice that is just starting to sublimate away as the Sun’s rays are getting stronger in this region.”

Hansen said these are dark barchan, or crescent-shaped dunes. During the winter, this region was completely covered with carbon dioxide ice, but now just the the tops of the dune have ice; also visible are what looks like white cracks, which is ice protected in shallow grooves on the ground. HiRISE will likely check back on this region later during the Martian summer to provide the science team with a seasonal sequence portfolio of images of the region, a benefit of having a mission in orbit for several years. MRO and HiRISE are workhorses, having been in orbit since March of 2006.

See the original image on the HiRISE website.

February 22, 2012December 24, 2015 by Nancy Atkinson

Gallery: Bizarre Dunes on Mars

These barchan (crescent-shaped) sand dunes are found within the North Polar region of Mars. Credit: NASA/JPL/University of Arizona

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Say the word “dunes” and the image that likely comes to mind is the sort of features you’d see in the Sahara Desert; huge mounds of carmel-colored shifting sand. But on Mars, dunes take on an entirely different connotation, and with the orbital eyes of the HiRISE camera on the Mars Reconnaissance Orbiter, we’ve seen some pretty bizarre-looking dunes. Take the image above for example, a newly released photo of well-speckled dunes in Mars’ north polar region. In this image, taken during the northern spring season, the dunes and ground are still covered in seasonal frost. “The speckled appearance is due to the warming of the area — as the carbon dioxide frost and ice on the dunes warms, small areas warm and sublimate (turn from solid to gas) faster, creating small jets that expose/deposit dark sand and dust onto the surface,” writes Serina Diniega on the HiRISE website. “Notice that there are no spots on the ground between the dunes — that is because the ground stays more uniformly cold, unlike the darker dune sand.”

See below for more weird dunes on Mars.

dunes 3 — Dunes in Aonia Terra on Mars. Credit: NASA/JPL/University of Arizona

These dunes look as through someone has thrown a rippled blue-toned cloth across Mars’ surface. HiRISE is monitoring these dunes in Aonia Terra for changes such as gullies, which form over the winter from the action of carbon dioxide frost. This image was taken on January 18, 2012 here on Earth, but the season in on Mars where this was taken was late fall in the Southern hemisphere. “Frost is just starting to accumulate here, and is concentrated on pole-facing slopes and in the troughs between the meter-scale ripples,” wrote HiRISE Principal Investigator Alfred McEwen.

dunes 5 — Dunes in Russell Crater Dunes on Mars. Credit: NASA/JPL/University of Arizona

speckled dunes — Pink dunes with black polka-dot speckles. Credit: NASA/JPL/University of Arizona

ESP_012801_1135_RED.abrowse — A wide area of dunes in Terra Cimmeria look as if they are being viewed under water. Credit: NASA/JPL/University of Arizona

dunes 6 — Fans and polygons on Dunes. Credit: NASA/JPL/University of Arizona

dunes 7 — Dark sand dunes at high Northern latitudes on Mars are covered seasonally by a layer of condensed carbon dioxide (dry ice), visible in this image. Credit: NASA/JPL/University of Arizona

Chocolate dunes? Credit: NASA/JPL/University of Arizona

See more great images from Mars on the HiRISE website