Ice excavated from the subsurface, by a crater 6m (20 feet) in diameter, sublimates away over the course of the martian summer. Each of these HiRISE images are 35m (115 feet) across and were taken in October 2008 and January 2009.
Image credit: NASA/JPL-Caltech/University of Arizona

An exciting new paper came out in yesterday’s issue of Science magazine, with HiRISE team member Shane Byrne as the lead author. Water ice has been discovered being exposed by fresh Martian craters!

This is exciting for several reasons: first, these are very tiny craters – only a few meters (yards) across. This means they’re not excavating very deep into the crust of Mars. So the ice has to be really shallow – less than a few feet below the surface! Secondly, the location of these craters is surprising – they’re between 40-55 degrees north latitude. This is far from the polar regions, where we’d expect to find ice (for example, where the Phoenix mission landed at 68 degrees north, ice was found by digging down into the dirt).

The third exciting aspect of this ice is its purity. We’d expect this ice to be mixed in with dirt and dust and rock. Instead, we found that it’s 99% pure ice! (Only 1% is dirt mixed in.) This can be measured because we watched the ice disappear over time. By taking repeated images of the same spot, HiRISE got a time sequence as the ice slowly faded. It faded so slowly that it has to be almost all ice – a dirtier mixture would have faded much faster as it sublimated (went directly from a solid to a gas) in Mars’s extremely dry atmosphere.

Speaking of dry atmospheres, this also has interesting implications about the history of the Martian climate – there had to have been more water vapor in the atmosphere in the recent past than we previously thought. We still have lots of questions about how this ice formed, how much of it there is, and how many more of these craters we’ll find. Luckily, we’ve got a long mission ahead of us to explore these issues!

This discovery is also a great example of how the instruments on MRO work together. CTX initially detected these new craters as “dark spots,” and HiRISE followed up to confirm that they’re really impact craters. Some of those HiRISE images revealed some very bright white material, and then CRISM confirmed that material really is water ice. The instruments worked together to accomplish the best combined science. Go team! ☺

Here are some more detailed stories, images, and multi-media:

• Really nice movie with Shane Byrne talking about the discovery and excellent animations showing the locations of the craters and the time-evolution of the ice disappearing: NASA multimedia – then go to “Video Gallery” on the right, and click on “Mars – Exposed”.

• NASA press release, and all of the images and materials from the press conference

• UA news story

We’ve seen many more news stories & blogs – thanks for the interest, everyone! It’s great that everyone thinks this is as exciting as we do! ☺

The HiRISE team met up this summer in Whitefish, Montana. In between meetings, we were also able to take several geologic field trips and hikes. Glacier National Park has many cool (haha) glacial features, of course, and we also learned about some interesting sedimentology that occurred in the ancient geologic past. The patterns we saw in the sedimentary rocks are similar to those discovered by the Mars Opportunity Rover – cross-bedding and festooned ripples that form when sand is laid down under a body of water. The shape and direction of the ripples can tell you how much water was present, how fast it was flowing, and whether it was a river, a lake, or an ocean. These are important questions we’d like to answer about the history of water on Mars.

The park also has wonderful examples of glacial geology. HiRISE has taken images of many features thought to be related to glaciers, so it’s important to understand the terrestrial analogs that lead scientists to think these are evidence of flowing ice on Mars. For example, we hiked along a moraine composed of jumbled rocks the Grinnell Glacier left behind as it flowed downhill. In addition to the remains of the (rapidly disappearing) glacier itself, we also saw typical glacial erosional structures such as U-shaped valleys, hanging valleys, and cirques. For a HiRISE image of cirque-like features, see PSP_005730_1405.

On one of our field trips, we were accompanied by reporter Michael Jamison of The Missoulian. This story was on the front page of the paper the following day:

I thought the story was really good – a quirky (but so are we!) description of why we would want to stare at the rocks in such a magnificent setting, and their relevance to our mission to Mars. We all thought it was funny when he called Alfred McEwen, our Principle Investigator, a “Marsman”!

HiRISE Team in Glacier National Park, in front of a classic U-shaped valley carved by glacial erosion.

This was originally posted here, written for the IAG Planetary Geomorphology Working Group’s featured image of the month. The author, Kathryn Fishbaugh, is a HiRISE team member, and she allowed us to post a copy of it here as well. It’s great to see the results scientists are getting from HiRISE images – and you thought they were just pretty pictures!

At the north pole of Mars lies Planum Boreum, a dome of layered, icy materials similar in some ways to the large ice caps in Greenland and Antarctica and comparable in size to the former. The dome itself consists of the polar layered deposits, consisting of over 90% ice with a little bit of dust, and the basal unit, consisting of ice, dust, and sand.

The image shows a cliff in the Polar Cap deposits. The upper portion of the cliff consists, for the most part, of fractured portions of the polar layered deposits and has a reddish appearance due to dust both coating and entrained within the ice (red arrow). Below that is the basal unit, with more flat-lying layers of blueish material that is basaltic sand (blue arrow) (like the black sand beaches in Hawaii). You might also notice some lighter colored layers. Those are also fractured and composed of ice and dust, like the polar layers above them. And at the bottom of the image, sand eroding from the basal unit is collecting into dunes (white arrow). The entire cliff is about 700 m (2300 ft.) tall (comparable to the depth of the Grand Canyon).

Scientists study past climates and trends in global warming on Earth by examining the air bubbles trapped within ice cores (long, cylindrical samples of ice, extracted with a drill) taken from Greenland and Antarctica. These ice cores contain ice created from last year’s snowfall to many hundreds of thousands of years ago and have trapped bubbles with the same atmospheric composition as existed when the snow fell. From this composition, scientists can figure out what was the contemporary temperature and hence how the climate has changed over time. Similarly, the ice in the polar layers and basal unit on Mars must also have recorded how the martian climate has changed. (more…)

I had the opportunity to attend the 40th annual meeting of the Division for Planetary Sciences of the American Astronomical Society. It’s being held here in Ithaca, NY at Cornell University. Along with some beautiful fall weather, I’ve also enjoyed some fantastic science. The meeting started with the Mars sessions on the first day. I think every single talk about the planet’s surface used HiRISE data! An entire session was devoted to the Martian atmosphere, which was interesting because I’m not as familiar with that. It’s also been great to see what’s going on in the rest of the solar system – I’ve been pretty Mars-oriented since starting with HiRISE, so I’ve loved hearing about things like the lakes on Titan, progress in exoplanet studies, and changes in Jupiter’s Great Red Spot.

As usual, other blogs are covering the meeting well (Planetary Society and the Martian Chronicles, for example). In addition, the sessions are all being web-streamed live (links to streaming video here; full program here). I think this afternoon’s special sessions are going to be really interesting, so I recommend watching them. I’m especially interested in the mission highlights from the rovers, Phoenix, MESSENGER, Cassini, and Kaguya. We’ve already seen some results from Kaguya and MESSENGER in the individual sessions – exciting stuff!

A number of our science team members are at LPSC, the annual Lunar and Planetary Science Conference, this week. This is a big gathering in Houston, Texas, where members of the planetary science community share their work from over the last year. Unfortunately, we don’t have an active blogger there, but I wanted to point out some other people sending out excellent reports about HiRISE science.

The Martian Chronicles has two great articles about presentations given by HiRISE Team Members: Spiders on Mars, from our Deputy PI Candice Hansen (more about this topic here, under “Spring at the South Pole of Mars”); and Layers and Swiss Cheese, which mentions two HiRISE people, Kathryn Fishbaugh and Shane Byrne. The polar group has been very active in helping to plan and target images, and their results are really cool (ha, ha!).

Star Stryder has also been at LPSC, with lots of stories through the week. The post Pingos, Polygons and other Puzzles mentions two types of Martian landforms I know members of our team are studying in HiRISE images, although there aren’t many specifics about their LPSC presentations. For some visuals to go along with the story, here are some HiRISE images of possible pingos and plentiful polygons.

I also thought their reports on speeches by the NASA bigwigs were very interesting: NASA Administrator Mike Griffin telling young scientists not to specialize in the face of changing funding priorities, and Alan Stern discussing possible MSL delays.

So, check out these reports, and if you see any other good ones, add a link below in the comments! Hopefully we’ll get more as the week progresses.

Today a press release went out about a forthcoming paper in the journal Geology (click here for full text online or here to download a PDF). John Grant, a Co-Investigator on the HiRISE science team, is the lead author, and most of the co-authors are also on our science team.

What is a megabreccia? A breccia is a jumbled-up mixture of broken rocks, cemented together by a finer-grained material. We see them in impact craters and volcanoes on the Earth, places where there was a lot of violent energy to break up rocks. A megabreccia is just a larger version of that – something we can see with HiRISE resolution, as opposed to something you’d have to pick up in your hand to identify. The megabreccia in Holden formed when the explosion that opened the crater shattered rocks, mixed them up, and then the fragmented ejecta collapsed back down into the crater. Before HiRISE, we didn’t have the resolution to detect these textures.

This is a cutout of an image taken in Holden Crater, showing the megabreccia texture, in false color as usual. A context map is shown to the right, showing where in the crater rim this image is located (click these images to enlarge). The blocks here are mostly darker, and they’re embedded in a lighter-toned material. The dark chunks are kind of “scooped out,” which means they’re more easily eroded than the surrounding light-colored rock. Scientists think this may be because they’re sedimentary rocks, formed at the bottom of a lake or river. The stripey dark blobs on top are sand dunes that are slowly covering up the area again.

This megabreccia is located in an area scientists find fascinating for other reasons, too: there are clays that were laid down over a long period of time when it had to be wet. This implies there was once a lake in this crater – perhaps more than once over its history. At one point, the lake broke through the rim of the crater, releasing a huge flood of liquid water. You can see the channel this formed in the context map above. This flood eroded away material that was covering the megabreccia, exposing it for HiRISE to see.

The HiRISE image PSP_003077_1530 shows another part of Holden Crater, and the caption includes more information about the geologic history of the area.

Three HiRISE papers are coming out in a special issue of the journal Science today. Our science team has been working hard on analyzing the images we take, and they’ve discovered some interesting things.

One paper talks about a few aspects of the history of water on Mars: HiRISE images of “rock glaciers” and bright deposits in gullies that might be extremely recent. HiRISE observations of an area called Athabasca Valles were used to show that it is actually covered with a thin veneer of lava. A third paper discusses thin layers in the North Polar cap. HiRISE is able to discern very fine layering (seen in an excerpt of image PSP_001636_2760 at left), as well as the color and thickness of each layer. Since these layers were laid down over hundreds of thousands of years of Martian history, they provide a record of climate change on the planet.

You can find a lot of things on the HiRISE website that are impossible to include in a print journal – like full-resolution color versions of the images from the papers, and (my favorite) cool 3-D flyover movies of the stereo observations. Our webmaster designed this lovely page for accessing these special products. Have fun flying over Mars!

We’re just finishing up four days of having the whole HiRISE team visiting us here in Tucson. It’s been a great team meeting! We had updates on operations, and heard a lot about science results from HiRISE images. Some CRISM and THEMIS team members participated, too, so we got to see what other teams are doing and talk about collaborating and using multiple data sets. People are doing really exciting things with HiRISE data!

Also, our team is really growing!

You’ll notice a lot of new faces compared to a few years ago!

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