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 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.

It was so exciting to find this image! The image was intended to be part of a series of seasonal monitoring observations of a dune field. We’re watching to see how the winter carbon dioxide frost disappears as spring comes to the northern polar areas (which is pretty cool in itself! See PSP_007043_2650, for example.) PSP_007338_2640 happened to be the first image we took after powering back on after a safing event. So we were examining the image to make sure the camera was still working OK (it is – as you can see from this beautiful image & the many others we’ve taken since!). If it hadn’t been for that, we might not have noticed this for weeks! (In case you haven’t noticed, we have a LOT of images to look at! )

My first reaction was just, “What is that?” So I asked some of the scientists around HiROC, and they got excited, too. Everyone was talking about it all day, putting together ad-hoc color products (the full color processing takes a while to get through our processing pipelines) and looking at other images nearby for similar events. Because this was part of a series of images in the same spot, we had a “before” image as well (PSP_007140_2640). It’s a little hard to compare the two images because the bright carbon dioxide frost is changing as well, and we took the two images from different angles. But you can see in the second image that there are some spots up above on the cliff that are missing their bright frost covering. Perhaps that’s where the rock (or ice) fall started? The springtime sun is warming these icy layers, which could cause sublimation (solid ice changing to gas). Certainly there is a lot of dust being raised to form this big cloud, too, whether the dust was mixed in with the ice blocks, or just kicked up off the lower, dustier layers. As we continue monitoring this site and other polar areas, we’re sure to learn a lot more about the processes captured in this image.

ETA: Emily Lakdawalla made a great animation of the before/after shots, posted on the Planetary Society blog. So cool!

1. Validate the image data that have arrived since last time I checked. Are the raw image files we receive gap-free and are the file sizes as expected? Did the Uplink team command the HiRISE camera properly? So far, they have a perfect record!
2. Keep checking to see if new data is arriving for processing.
3. Are our automated processes running properly?
4. Is the data being stored correctly and can the team access the images in the appropriate places?
5. Finally! Actually look at the new images. In between “oohs” and “ahhs” check to see that the images look good. Did our automated software handle the data correctly? Do I need to do any manual reprocessing of image data?
6. Report my findings to the team via email.
7. Get up and see what the scientists and other team members are up to.
8. Eat some Cheetos.
9. Repeat as necessary.
10. A million other tasks.
    

By the end of the day I am covered in Cheeto dust (joking) and amazed by some new vista of Mars (seriously).

What is it we find so amazing? I can only speak for myself, but in observation TRA_000823_1720, the boulders lying about casting shadows indicate just how “Hi” resolution the HiRISE camera can go. In the second observation – TRA_000825_2665 – the stack of water ice and dust layers and the patches of water frost make for a distinctive landscape. At this resolution, there is a marked difference between the north polar region on Mars and the pictures I have seen of the Earth’s own polar regions.

To me, this is the great joy of planetary science: seeing new vistas that are at once familiar and unfamiliar, and never, ever routine.