[meteorite-list] New Mars Reconnaissance Orbiter Images

[Ron Baalke]

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.