Evidence of Fractures in NPLD and Their Significance to the Formation of Martian Polar Spiral Troughs.
Zuoxun Zeng1,2, Nathaniel E. Putzig3, Hongjie Xie2, Stuart J. Birnbaum2, Stephen F.Ackely2 and Lilin Liu1.
1China University of Geosciences, Wuhan, 430074, P.R.China, 2University of Texas at San Antonio, 78249,
USA, zuoxun_zeng@hotmail.com, 3Southwest Research Institute, Boulder, CO 80302, USA
Introduction ： Understanding the structure and
stratigraphy of polar ice is an integral part of
unraveling
the history of
its
formation and
implications for past and present climate [e.g., 1, 2].
Earlier studies of the North Polar Layered Deposits
(NPLD) in Planum Boreum on Mars have provided
valuable insight into the nature of these materials [3].
Radar sounding results show angular unconformities
within the NPLD that are interpreted as erosional
periods within climatological cycles [4]. Here, we
present evidence of fractures in the NPLD based on
interpretation of MOC images and radar sounding
data, and we discuss the significance of these
fractures to the formation of Martian polar spiral
troughs.
Evidence from MOC images: We observe abundant
indications of fracturing within the NPLD in MOC
images. Figures 1a,b,d,e show four fracture examples
at different scales. To illustrate the existance of
similar cases in the South Polar Layered Deposits
(SPLD), we include one image from that region (Fig.
1c). Figure 1a shows a huge en echelon fracture zone
and its corresponding en echelon fault basins. The
structural zone, as a whole, trends sub-north-south
while the fractures and long axes of the basins trend
north-north-west. The orientation of faults, fractures,
and basins indicates this area experienced left-lateral
shear. Figure 1b shows two sets of conjugate
fractures and rhombic fault basins. One set of
fractures trends north-north-west, and the other one
trends west-north-west. Similarly, Fig. 1c from the
SPLD shows two sets of conjugate fractures and a set
of en echelon fractures