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The Planetary Society Blog
By Emily Lakdawalla
Tons of new image releases from Mars Reconnaissance Orbiter's other instruments
Dec. 13, 2006 | 14:47 PST | 22:47 UTC
So far, most of the news I've written here about Mars Reconnaissance Orbiter has been in the form of stunning HiRISE images. (See here and here and here and here, for instance.) But today, a slew of press releases coming out of NASA, JPL, and ESA have included images representing data from two of Mars Reconnaissance Orbiter's other key instruments: CRISM and SHARAD.
CRISM, the Compact Reconnaissance Imaging Spectrometer for Mars, produces stupefying quantities of data about Mars. Spectrometers gather spectral information about their targets. What that means is, they gather information about how strongly a target reflects (or emits) radiation at a variety of wavelengths. CRISM is hyperspectral, meaning that it is capable of splitting the incoming radiation into 544 "bands" -- 544 little slices of the electromagnetic spectrum -- providing incredible resolution of the composition of the target. Most of the time, in order to pay for spectral resolution, you sacrifice spatial resolution, which means that these massive spectral measurements are taken across wide areas of the target planet at once. The Thermal Emission Spectrometer on Mars Global Surveyor, for instance, gathered spectra for chunks of Mars a few kilometers square. But CRISM doesn't only have spectral resolution, is has spatial resolution of 18 meters per pixel. That qualifies it as one of the higher-resolution cameras sent to Mars; it's similar in quality to HRSC on Mars Express and compares well to Viking's highest resolution shots. But it takes those high-resolution images in 544 different colors at once. It boggles the mind. (For more on this, check out a past blog post on various Mars camera resolutions.)
Enough ranting; here's my favorite CRISM shot from today's releases. Clay and olivine in Nili Fossae, MarsClay minerals were originally spotted in Nili Fossae by the OMEGA instrument on Mars Express. These views were captured by Mars Reconnaissance Orbiter using its high-resolution camera, HiRISE, and its hyperspectral imaging spectrometer, CRISM. The upper left frame is a context image; the other three frames show zoomed-in views.
The detailed shapes of the rocks are from HiRISE; the green and red colors are from CRISM, and represent the strengths of spectral absorption bands due to minerals present in the scene. Red stands for olivine, and green for clay minerals. The greenish clays tend to be associated with exposed bedrock, while the red olivine minerals appear as sand dunes. Taken together, this suggests that the clay minerals are the oldest exposed materials, and the olivine-rich sand dunes have been deposited on top of them. Credit: NASA / JPL / JHUAPL / Brown U. |
As with my previous post, you can see here the power of employing two different instruments together to tease out a geologic story. HiRISE has the sharp vision; CRISM can gather the compositional information at lower (but still impressive) resolution. And it sure tells an interesting story here. Nili Fossae contains lots of olivine-rich sand dunes (the red stuff), like many places on Mars. But where those sand dunes are absent, you can see cracked bedrock, bedrock that contains the telltale spectral signature of clay. Why do we care? Because within their crystalline structure, clay minerals contain lots and lots of water. This would be one great place to send another lander to "follow the water."
Here's my other favorite from today's releases, from yet another instrument on Mars Reconnaissance Orbiter, SHARAD.SHARAD view of Mars' north poleThe upper right panel contains a radargram from the Shallow Subsurface Radar (SHARAD) on Mars Reconniassance Orbiter. SHARAD has detected detailed structure in Mars' north polar layered deposits (PLD). The radargram represents the strength with which SHARAD's broadcast radio waves were reflected back at the orbiter; the vertical scale on the radargram is the time delay between the broadcast and the received echo. Credit: NASA / JPL-Caltech / ASI / University of Rome / Washington Universtiy in St. Louis |
SHARAD has here revealed incredible detail in the subsurface layering on Mars. I can't tell you as coherent a story from these pictures as I could from the CRISM data, but I can tell you that SHARAD's ability to resolve these layers is important. Geologic remote sensing is generally hampered by our inability to see beneath the surface. On Earth, geologists employ tricks like drilling deep cores to get a vertical view of the rocks under our feet, and how they relate to each other. Such a vertical view is really critical to understanding the geologic history of a place. The SHARAD views released today are all polar ones, meaning that we're primarily seeing layers formed in very ice-rich materials. I will be very curious to see SHARAD results from rockier places.
You can see all the other image releases at the Photojournal, as usual.
Also, it seems that the HiRISE team has released another new batch of images today. I just can't keep up with this flood of data! Many people have asked me to post something about the Viking landing sites. That's on my list -- I just haven't had time yet to do the subject justice.
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