http://www.planetary.org/blog/article/00000779/
The Planetary Society Weblog By Emily Lakdawalla New Mars Reconnaissance Orbiter Images November 27, 2006 Over the Thanksgiving holiday, the Mars Reconnaissance Orbiter HiRISE imaging team gave us all a gift: the release of 31 new images from the "transition phase" of MRO's operations at Mars. This is a new data set so it's going to take a little getting used to. The images are magnificent in their scale and detail but that creates problems -- they're enormous files, and difficult to handle unless you've got a pretty souped-up computer. My computer is not particularly souped-up, unfortunately. Whenever I manage to beg and plead and whine a new computer out of Lou, I don't have a lot of money to spend, and I always spend what I've got to get the highest-resolution screen available. Which means I make sacrifices in memory, hard drive space, and processing speed. So I'm having a tough time handling these monster images. The HiRISE team recognizes that this is a problem for people and are working on developing some online viewing tools that will enable visitors to view the full-resolution data without having to download and manipulate files that are hundreds of Megabytes in size. In the meantime, though, if you want to see the details, you have to put your modem and your computer to some serious work. It's doable, but painful. The pain's worth it in the end -- just scroll down to see for yourself. Here's what you need to do. First, clean off your hard drive to make space for a couple of gigs of image data, especially if (like me) your chosen image viewing software is Photoshop. Photoshop employs the hard drive as a scratch disk to save intermediate versions of images -- the "undo levels" -- so you need to leave a few gigs of space free on your drive at all times to keep the software happy. You don't, however, need Photoshop to view these images; HiROC suggests the use of a JPEG2000 viewing browser plug-in called ExpressView <http://www.lizardtech.com/download/dl_options.php?page=plugins>, which is free and easy to download and install. To open the JPEG2000 images in Photoshop, I needed to download and install a Photoshop plug-in to handle these files, which I got here <http://www.leadtools.com/Utilities/PSPlugIn/PhotoShop_plug-in.htm>. I'm sure there are other PhotoShop plug-ins available. Having prepared my computer, I can now get down to the business of poring over the incredible details in the HiRISE pictures. This one looked pretty cool: Eos Chasma Olivine (TRA_000835_1670) <http://hiroc.lpl.arizona.edu/images/TRA/TRA_000835_1670/>, and moreover, it was a relatively petite 29 Megs to download. The click-to-enlarge version below shows the area at 1/8 its full resolution, or 4 meters per pixel. HiRISE Image of the wall of Eos Chasma This image was captured during the Transitional Phase of Mars Reconnaissance Orbiter's operations at Mars. It covers an area of about 5,500 by 3,200 meters and shows the steep walls and dune-filled canyons of Eos Chasma, part of the Valles Marineris system. The scene is illuminated from the west. Source <http://hiroc.lpl.arizona.edu/images/TRA/TRA_000835_1670/> Credit: NASA / JPL / U. Arizona I wasn't disappointed by the detail visible in the full resolution version. I picked out two cool spots to show you at their full resolution. Here's a context photo showing where the two detailed views are: Eos Chasma as seen by HiRISE: Context map for detail images Credit: NASA / JPL / U. Arizona The first one shows sand dunes in the floor of the canyon. Look at all the beautiful different shapes that the dunes make as a result of what must be fairly capricous winds rounding the corner of the topographic high that comes in from the lower right. At the toe of the topographic high, at the lower center of the image, you can see a few boulders that have fallen down the cliff. At a few pixels across, they're on the order of 1 to 10 meters across -- the size of cars or trucks. Sand dunes within Eos Chasma This detail from a HiRISE image of Eos Chasma, Mars, is shown at its full resolution of 50 centimeters per pixel. A field of sand dunes on the left breaks into a variety of forms as it moves around a topographic high to the lower right (southeast). The entire image covers an area only 250 meters square, roughly the size of a football stadium. Credit: NASA / JPL / U. Arizona The next detail shows a beautiful fan-shaped debris deposit. The debris fan is made of lighter-toned material -- possibly closer in size and composition to the bright wall rocks -- than the dark stuff that makes up the sand dunes filling the canyon floor on the left. Debris fan within Eos Chasma This detail from a HiRISE image of Eos Chasma, Mars, is shown at its full resolution of 50 centimeters per pixel. A fan of debris cascades down a narrow canyon from southeast to northwest. The entire image covers an area only 250 meters square, roughly the size of a football stadium. Credit: NASA / JPL / U. Arizona You might think this image looks a little fuzzier than the previous one, and you're not wrong about that. This part of the picture, closer to the edges of the HiRISE image, is made from data that was "2 by 2 binned" before it was sent to Earth. In other words, the data was compressed by averaging the values of four pixels together, reducing the native resolution of the image to 1 meter per pixel. Most HiRISE images will be treated like this, with the center of the swath returned at its highest resolution, and the sides of the swath returned at a reduced resolution, in order to save on precious bandwidth. It may seem sad to return data that's less sharp than the camera's capable of, but it's better to return more images with reduced resolution than fewer images at the highest possible resolution. Having successfully dealt with a 30-Megabyte file, I decided to rev my computer up and try one of the 200-Meg files. HiRISE is taking a lot of images of the northern plains right now for two reasons. First of all, they are mapping out potential landing site locations for the Phoenix </explore/topics/phoenix/> polar lander, to help the team pick the best possible spot. Second of all, it's shortly after the northern summer solstice now, which means that the northern polar regions are the best lit that they will be for the next Martian year; the Sun's at pretty much its highest northern migration and is moving south in the Martian sky with every passing day. Now, the northern plains are pretty dull-looking at low resolution. Zoom in, though, and you reveal surprising details. Take this location, for instance, which I'm displaying at 50 meters per pixel. This is sharper than most Viking images and Odyssey THEMIS infrared images, but less sharp by a factor of two or three than THEMIS VIS or Mars Express HRSC. HiRISE image of the northern Martian plains: 50 meters per pixel HiRISE image of the northern Martian plains: 50 meters per pixel Credit: NASA / JPL / U. Arizona Okay. So let's zoom in on a region near the center. This view is at 10 meters per pixel. At this scale, you can start to see the featureless gray plains break up into some kind of regular cell-like pattern. There's also a dark splotch near the center, presumably a buried crater. HiRISE image of the northern Martian plains: 10 meters per pixel Credit: NASA / JPL / U. Arizona OK, let's zoom in more, onto the upper left side of that buried crater. This view is at a MOC-like 2 meters per pixel. HiRISE image of the northern Martian plains: 2 meters per pixel Credit: NASA / JPL / U. Arizona And, finally, the full HiRISE resolution of 50 centimeters per pixel. HiRISE image of the northern Martian plains: 50 centimeters per pixel Credit: NASA / JPL / U. Arizona The shoulder of that "buried crater" has broken up into a field of boulders that appear to be perched atop the patterned ground of the northern plains. If that patterned ground were on Earth, geologists would tell you that the patterns result from the expansion and contraction of buried water as it freezes and thaws. On Mars, water isn't supposed to thaw -- but you see patterned ground like this all over the northern plains, and we also know that there's water ice buried under the surface, so there must be some connection. That's one of the things that Phoenix is going there to discover. That's about all the acrobatics my computer can take for the day. I tried to open a 400-Meg image that looked like it had an interestingly different type of patterned ground in it, but it appears that the attempt has ground Photoshop to a halt. I'll have to find me a beefier computer and have another try another day. ______________________________________________ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list