Analyzing the temperature and mineral composition of the Olympus Mons, the Valles
Marineris
Introduction
Mars is the Earth's outer neighbor; it is the fourth planet from the Sun. The first historical
study of Mars was credited to Francisco Fontana, who rendered telescopic observations in
1638. Around 1877, Giovanni Virginio Schiaparelli described the “canali” or channel
formations in the planet. But it was not until 1965 that the first close-up picture of Mars
revealed a world strangely familiar, yet different enough to challenge our perceptions of what
makes a planet work. Although spacecraft have shown us that Mars is rocky, cold, and
sterile beneath its hazy, pink sky, scientists presume there was an early warm period and that
the heat from inside Mars probably caused the volcano’s formation as well as the continental
drift.
In order to better understand the geological features, water resources, climate and biological
aspects of the red planet several spacecrafts including orbiters, landers, and rovers have been
sent by the Soviet Union, the United States, Europe, and Japan.
The Mars 2001 Odyssey is an orbiter that was launched from Kennedy Space Center on 7
April 2001, it carries three main science instruments: The Gamma Ray Spectrometer (GRS),
the Mars Radiation Environment Experiment (MARIE) and the Thermal Emission Imaging
System (THEMIS). This last one combines a 5-band visual (VIS) spectral resolution
imaging system with a 10-band spectral resolution infrared (IR) imaging system. The IR
subsystem has a 100m/pixel spatial resolution while the VIS subsystem has a 19m/pixel
resolution. THEMIS began observing the surface and atmosphere of Mars in February 2002
with the use of thermal infrared multispectral imaging between 6.5 and 15 m and visible to
near-IR images from 450 to 850 nm. Some researchers have exploited the unique aspect of
investigating images of Martian temperatures at a resolution of 100 m. Not surprisingly, the
temperatures are related to material properties, such as composition and structural integrity,
climate and topography, which indicate the origin, evolution and history of the planet.
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A major result of the Mars Global Surveyor (MGS) imaging was the discovery of rock units
that are layered at a meter to ten meter scales. For THEMIS IR a major result from the
camera is the discovery that the physical and compositional properties of these layers can
vary, implying temporal changes in the processes or environments that formed the different
units. A key element of this discovery is the exposure at the surface of materials that directly
reflect the properties of the underlying rock unit from which they were derived.
Statement of the Problem
In order to better understand Mars, the sites of Olympus Mons, and Valles Marineris were
studied by utilizing THEMIS remote sensing imaging:
1. It is believed that since Olympus Mons is an extinct volcano that measures 24 km (15
miles) high, and the top of it is 70 km (40 miles) wide; the base is about 600 km (375
miles) wide. Therefore, it was originally hypothesized that basalt, pyroxene, granite and
possibly gneiss, schist, slalte, marble might be present at this site. These goals were
modified from the initial proposal and are discussed below.
2. Valles Marineris is 4000 km (2500 mi) long and reaches depths of up to 7 km (4 mi) and
widths of up to 200 km (125 mi). Most researchers agree that Valles Marineris is a large
tectonic "crack" in the Martian crust, forming as the planet cooled, affected by the rising
crust in the Tharsis region to the west, and subsequently widened by erosional forces.
Therefore, the initial goal was to test for the presence of water and minerals such as
basalt, pyroxene and granite. The goals were also modified and are discussed below.
Objectives & Methodology
For the purposes of this project, the data used was derived from THEMIS to analyze the
surface temperatures of two Martian sites as well as mineral compositions. The spectral bands
scrutinized for this study involved the visible, ultraviolet (UV), and infrared (IR) ranges of the
spectrum. All of the data utilized ISIS to process the images in order to view all 10 spectral
bands. ENVI was used to analyze the range of spectral bands, once processing was complete. By
using ENVI’s spectral library, it was believed that Martian minerals could be identified from
inherent spectral signatures and correlated to minerals found on Earth.
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Analysis
As stated in the initial proposal, the project’s goals were to assess the mineralogy,
temperature, and to investigate the presence of water in a region of Valles Marineris (Figure-I)
and to assess the same parameters in a region of Olympus Mons (Figure-II). By using images
from THEMIS, it was believed that the goals outlined above were quite attainable.
Unfortunately, Martian the data utilized from THEMIS was problematic and consequently only
thermal assessment and image classification was undertaken.
Figure-I Valles Marineris
Figure II- Olympus Mons
All THEMIS derived data exist as visible apparent brightness records (VISABR) and infrared
brightness temperature records (IRBTR). These two datasets are collected as QUBE objects,
which comply with the Planetary Data System (PDS) standards. A QUBE is an array of sample
values in two dimensions. The “core” of a THEMIS QUBE is three-dimensional, with two
spatial dimensions (samples and lines) and one spectral dimension (bands). The QUBE format
allows THEMIS data to simultaneously a set of images (at different wavelengths) of the same
target area, and also a multi-point spectrum at each spatially registered pixel target area (FigureIII). Additional information may be stored in “suffix” planes (back, side, or bottom) as
conceptually depicted in Figure-IV.
Figure-III THEMIS QUBE core structure
Figure-IV Exploded view of PDS QUBE
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The QUBE object’s complexity proved to be a significant obstacle for evaluating any data
derived from THEMIS. An ENVI software package was used for analyzing the Martian data.
Regrettably, ENVI cannot directly read the complex QUBE files. Consequently, a separate
software called ISIS 3.0 Beta, which is provided free pf charge through the USGS Astrogeology
Research Program at was needed to process the images. Moreover, the obstacles regarding
Martian data were compounded by the fact that ISIS is supported only by a Linux operating
system. Though ISIS has many image processing applications available, only two were needed
to complete the project. The first is a THEMIS to ISIS (thm2isis) application which converts a
THEMIS QUBE file to a .cub file. Once converted to a .cub file, the data was further processed
by using the ISIS to TIFF (isis2tif) application, which converts a .cub file to a .tiff file.
However, one should note that each band for a given data file must be converted to a separate
.tiff file. For example, if a 10-band RDR.QUB file has been chosen, the end result will be 10
separate .tiff files for that single image. The bands must then be stacked together as an ENVI
standard image for analysis. Once converted to .tiff files, the header files required editing. The
entire process proved to be tedious and time consuming. The steps involved in processing an IR
RDR. QUB file are outlined below in Figure-V.
Figure-V (IR RDR.QUB data processing)
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Acquire
file from
THEMIS
Edit band
centers
Input band
center
information
again
Covert to
.cub file
Convert to
.tiff file
Perform band math using
((band multiplier*B1)+Base)*1000
on each band
Input band
width
information
again
Edit band
widths
Stack bands
as ENVI
standard
Perform
data
analysis
As demonstrated in Figure-V, simply reaching a point where the data is in a useable form is a
complex procedure in itself. The data for the visible images utilized a similar method except for
two differences. To convert from Kelvin to Celsius the following formula was used: (B1*1.8459.637). The other formula used for the band math portion was: (B1*SF) + offset, where SF is
the scaling factor.
Once the cumbersome image processing was completed, analysis of the images using ENVI
was performed on the two sites. The initial site evaluated was Olympus Mons (Figure-IV). The
volcano is nearly 27 km high; it is over 20 times wider than it is tall. Thus, most of the volcano
has a fairly gentle surface slope. The image also shows the distinct cliff which marks the base of
Olympus Mons. In places, this scarp is up to 6 km high. In other places, it is hidden under lava
flows cascading out into the surrounding lava plains. This cliff is unique among the giant shield
volcanoes on Mars. The rough, crinkly patches around Olympus Mons are also unusual and form
the Olympus Mons Aureole.
Though is has been stated that the area of Olympus Mons was studied, only a very small area
near the base of the volcano as depicted by the arrow in Figure-VI was the true study area. The
actual image or swath (Figure-VIII) was comparatively much smaller yet abundant in data and
information. Figure-VIII illustrates the difficulty associated with obtaining both visible and
infrared spectral bands. The red swaths are the available IR sites whereas the purple boxes are
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the available visible sites. Therefore, with limited choices, the area of study was chosen solely
on obtainable visible and infrared information and not as a matter of preference.
Figure-VI Enhanced area of study
Figure-VII Swath of area studied
Figure-VIII Available Vis and IR sites
Figure-IX below shows a screen capture of analysis performed in ENVI on a portion of the
image swath collected from Olympus Mons. The first image is a density slice measuring a
temperature range of -27F to 4F. The middle image is band 9 of the IR image and the last
image on the right is the visible image. As a point of reference the bolder depicted by the arrows
was used to ensure that the same area could be viewed in three different frames.
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Figure-IX Volcano
Density Slice
IR image
Visible image
The temperature data gathered revealed that there was approximately a thirty-one degree
difference among the various areas calculated in the density slice. Much of the density slice area
shown is dominated by the colors magenta and cyan which had calculated temperature ranges of
-7.5522 F to -3.6582 F and -11.4461 F to -7.5522 F respectively. Yellow was the next most
abundant color. It ranged from -15.3401 F to -11.4461 F. It is difficult to verify the
temperature consistency at this location. Though, since Olympus Mons possesses different
heights, it was pressumed that the temperature variance is most likely attributed to elevation.
Further analysis of the temperature in this region was conducted by examining all 10 IR and 5
Vis bands individually in ISIS after conversion to tiff files. The tiff files were then individually
edited, stacked together, and scrutinized by performing an IR z-profile analysis. The two plots
generated by the z-profile analysis can be viewed in figures Xa and Xb. Figure-Xc, represents
both spectral plots for the Volcano Site. Unfortunately, the main goal of the research project
could not be derived in part due to the inability of obtaining the true kinetic temperature a Mars.
Accordingly, emmissivity could not be calculated in order to make a comparison of Earth’s
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mineral library to that of Mars. Yet, if emmissivity could have been obtained, several obstacles
remained such as the need to consider atmospheric correction and assessment of interference due
to Martian dust.
Figure-X
Figure-Xa IR z-profile plot
Figure-Xb Vis z-profile plot
Figure-Xc
However, a region of interest was selected in which an image analysis was performed to compare
similar physical or chemical characteristics (Figure- XI). In this case the region selected was one
pixel within the red box illustrated in (Figure- XIb) and further clarified by the black arrow. As
revealed in (Figure XIc) there was a significant similarity throughout the entire image. This
effect is attributed to the fact that this particular image is a slope from a volcanic site. Therefore
it is presumed that any ancient erupted material would have been evenly distributed along side
the volcano or at base of the volcano. The image below (Figure XIc) appears to support this
presumption.
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Figure XI Radiance
Figure XIa Density Slice
Figure XIb IR image
Figure XIc Image classification
Canyon Region (Valles Marineris)
The Valles Marineris is a system of canyons located just south of the Martian equator. The
system is about 4000 km long. Comparatively, the same canyon would extend all the way across
the United States. The central individual troughs, generally 50 to 100 km wide, merge into a
depression as much as 600 km wide. In places the canyon floor reaches a depth of 10 km, 6 to 7
times deeper than the Grand Canyon. As with the Olympus Mons site, only a small area of
Valles Marineris was studied. Figure-XII is an enhanced image of the region while figure-XIII
shows a swath of the actual study area. The same methodologies which were applied the
Olympus Mons site were applied to the Valles Marineris site and are discussed below.
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Figure-XII Enhanced area of study
Figure-XIII Swath of area studied
The temperature data gathered revealed approximately a thirty-seven degree difference among
the various areas calculated in the density slice (Figure XI). Much of the area shown was
dominated by the colors magenta and cyan which had calculated temperature ranges of -5.1908
F to -0.5448 F and -9.8368 F to -5.1908 F respectively. Yellow and maroon, were the next
two most abundant colors. Yellow ranged from -14.4828 F to -9.8368 F, while maroon ranged
from -0.5448 F to 4.1012 F. However, as with the Olympus Mons site it was difficult to verify
the temperature consistency at this location aside for the approximation displayed by the data.
Figure-IX Canyon
Density Slice
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IR image
Visible image
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Analysis was performed on the Valles Marineris site consistent with the methodology applied to
the Olympus Mons site. The radiance was calculated for the 10 infrared bands as well as for the
visible and a final plot was obtained to depict their differences. These results are shown in
Figure X. Figure Xa shows the z-profile analysis for the IR image while Figure Xb shows the zprofile analysis for the visible image. Figure Xc illustrates the combined analysis as one graph.
Figure-X Radiance
Figure-Xa IR radiance
Figure-Xb Vis radiance
Figure-Xc Combined IR and Vis
Contrary to the volcano site, which showed continuity throughout with regard to the image
classification, the Valles Marineris site showed significantly different results. Only the
immediate area surrounding the impact crater exhibited physical or chemical characteristics
which were similar to the area selected. One possible theory for explaining this phenomenon
would be to suggest that similar material surrounding the crater was scattered in the general
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vicinity of the crater upon impact from a terrestrial body. The similar material, of course, would
be that of the foreign body which impacted the site. Therefore, only the general area around the
crater would be expected to consist of similar mineralogy. The rest of the study area would be
expectedly different, which is what was observed.
Figure XI
Figure XIa Density slice
Figure XIb IR image
Figure XIc Image Classification
Conclusion
Due to limited data availability and difficult image processing, only analysis of radiance in
relation to the individual wavelengths in each spectral category (IR and Vis) could be pursued.
Though the results of this study yielded interesting results, the lack of ground-truthing
temperature data prevented the calculation of emmissivity. As stated earlier, the kinetic
temperature of Mars could not be derived. In order to make mineralogy comparisons between
Earth and Mars, emmissivity which is calculated from Mars kinetic temperature, must be
obtained. However, this does not imply that had emmissivity had been calculated that
mineralogy could be confirmed. The presence of minerals such as basalt, pyroxene and granite
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is inherently difficult to evaluate due the influence of other factors. Because further work is
needed to remove atmospheric interactions and other environmental interactions that could affect
the results yielded, the information obtained is at best an approximation based on the technology
available.
Despite the problems associated with deriving mineralogy results, this study did produce
interesting findings. From the results obtained it was noted that the physical/chemical
composition surrounding the volcano site was consistent throughout the image, while the crater
area analyzed in the Valles Marineris site displayed similarity only with the impact area. In
addition, it was confirmed by the image classification, that regardless of the temperature of an
object, the radiance for different substances with different physical and chemical properties
reveals subtle differences when compared as a whole. The significance of this research is that
the calculation of radiance is the most appropriate parameter for remote sensing of terrestrial
bodies.
References:
http://themis-data.asu.edu/
http://volcano.und.nodak.edu/vwdocs/planet_volcano/mars/Shields/olympus_mons.html
http://astrogeology.usgs.gov/Projects/VallesMarineris/
http://isis.astrogeology.usgs.gov/
http://www.msss.com/moc_gallery/
http://astrogeology.usgs.gov/Projects/MDIM21/#Download
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