Sixth Mars Polar Science Conference (2016)
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OBSERVATION OF SEASONAL VARIABILITY OF LANDFORMS IN THE MARTIAN SOUTH POLAR
REGION J. Hao1 , S. van Gasselt2 , A. Neesemann1 1 Freie Universität Berlin, Inst. of Geological Sciences, Planetary
Sciences and Remote Sensing Group, Malteserstr. 74-100, 12249 Berlin, (Germany); [email protected];
2
University of Seoul, South Korea, 163 Seoulsiripdae-ro, Dongtaemun-gu
Introduction: During the past fifty years the Martian southern polar cap has been extensively studied at
varying scales. Though small-scale investigations focused on studying the polar cap as a whole dominated
the first years of observations [1-3], further development
of camera systems now allows studying small features
on a much larger scale. As geomorphological surface
changes on Mars occur mainly on larger scales, it is important to observe these changes in high detail in order
to understand the distribution, temporal variability and
spatial changes as well as their interdependencies. The
amount of data collected over the last decades will also
allow us to characterize and study not only seasonal but
also annual changes.
However, while landforms have been studied in much
detail [4-11] and many aspects of their temporal and
spatial variations have been unraveled, only relatively
few works focus on the interdependences of features
within their environmental context as defined through
atmospheric and topographic, as well as morphometric
parameters.
In order to investigate these, we chose what we believe
is a representative area located in the south-polar deposits which exhibits significant morphological changes
throughout a Martian year and which has been covered
by multi-temporal observations at different scales to allow the study of details as well as context (see Fig.
1). We have used high-resolution images and data obtained from the Mars Observer Camera (MOC-NA), the
Context Camera (CTX), the High Resolution Imaging
Science Experiment (HiRISE) and the High Resolution
Stereo Camera (HRSC) at scales of 0.5-15 m per pixel
to perform visual studies of features. Furthermore, the
Thermal Emission Spectrometer (TES) and the Thermal
Emission Imaging System (THEMIS) data were used
to derive environmental parameters helping to put these
image observations into a seasonal environmental context. Topography data from MOLA, HRSC and MRO
stereo observations are used to assess topographic effects and to study insolation characteristics and budget
in relation to slope azimuth and exposure.
Background: It has been known for decades [1214] that the southern polar cap of Mars is basically composed of H2 O ice, CO2 ice and dust. These components
directly interact with the atmosphere, which causes the
polar region to undergo seasonal changes and which are
sensitive indicators of the global climate. South polar
landforms are a direct result of seasonal conditions and
short-term changes of the Martian environment but they
Figure 1: Grid-based mapping approach. a) Spiders, b) Polygonal
terrain, c) Dark/Dalmatian spots, d) Dunes, e) Swiss cheese, f) Gullies.
also reflect longer-term effects of climate and geological processes, the interaction of H2 O and CO2 ices as
well as dust dominated landform expression and play a
crucial role in the Mars global energy balance and evolution history [15-16]. Therefore, studying changes of
landforms and their geomorphological expression over
periods longer than few seasonal cycles may help to assess and constrain effects and perhaps even climate variations in greater detail [e.g., [17]] as they are important
clues for understanding the geological and climatic evolution of the planet.
Methodology: In order to study surface features in
detail and systematically, we divided the research region
(Cavi Angusti City, 285◦ S - 301◦ S, 79◦ E - 85◦ E) into a
grid of 10 km x 10 km (Fig. 2) to trace the occurrence of
features within each grid cell. The collected data from
this survey are placed within a Geographic Information
System in order to maintain the spatial context. We employed a sinusoidal coordinate system in order to main-
Figure 2: Characteristic landforms in the south polar region. a) Spiders, b) Polygonal terrain, c) Dark/Dalmatian spots, d) Dunes, e)
Swiss cheese, f) Gullies.
Sixth Mars Polar Science Conference (2016)
Figure 3: Examples showing the spatial relation of spiders,
dark/Dalmatian spots and polygonal terrain.
Figure 4: Changing surface morphology over time at the example of
a spider network in the south polar region. a) MOC image M1001405
(12/12/1999), b) CTX image P06_003514_0985_XI_81S064W
(04/27/2007), c) CTX image B10_013456_0984_XI_81S063W
(06/09/2009).
tain an equal-area mapping framework and to calculate
extents of features properly.
We also developed indices to quantify and qualify
these changes and distribution. The expected result includes the mapping of landforms as function of spatial
context and seasons over 10 Martian years. Datasets
covering these spatial and temporal frames were manually co-registered to minimize offsets introduced during
standard processing.
Approach: We initially focused on polar spiders,
polygonal terrain and dark spots as these features have
been well-described in the literature and their formation
mechanisms are well known [4-7].
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Preliminary results and discussion: We mapped
the distribution of landforms in study area (Fig. 4).
From this, we can see that spiders, dark spots and
polygonal terrain overlay each other to a large extent.
Dark spots often also occur in close vicinity to spiders and polygonal terrain. Our initial findings show
that black regions around the spiders sometimes exhibit slight changes even over the course of few days,
mainly occurring during late spring. The most dramatic
changes we have observed took place between the end
of May and the beginning of June in the year 2009.
Next Steps: With data acquisition on environmental conditions we will continue to identify landforms
and changes, and focus on investigating how far and in
which way they are controlled and affected by environmental parameters.
References: [1] van Gasselt et al. (2005) JGR 110
(E8). [2] Carr (2006) The Surface of Mars, XIV+307. [3]
Jian and Ip (2005) ASR 43, 138-142. [4] Mutch (1977) JGR
82, 4389-4390. [5] Thompson and Schultz (2007) Icarus
191, 505-523. [6] Piqueux et al. (2003) JGR 108 (E8). [7]
Kieffer et al. (2000) 2nd MPS (Abs. #4095). [8] Piqueux and
Christensen (2008) JGR 113 (E6). [9] Seibert et al. (2001)
GRL 28, 899-902. [10] Titus et al. (2004) 35th LPSC (Abs.
#2005). [11] Marchant et al. (2009) 40th LPSC (Abs. #1616).
[12] Leighton and Murray (1966) Science 153, 136-144.
[13] Kieffer et al. (1976) Science 194, 1341-1344. [14] Barlow (2008) Mars: An Introduction to its Interior, Surface and
Atmosphere, XII+264. [15] Tamparri et al. (2008) PSS 56,
227-245. [16] Philip et al. (2007) Icarus 192, 318-326. [17]
Thomas et al. (2000) Nature 404, 161-164.