1. REFERENCES
RECURRING SLOPE LINEAE FORMATIONS ON CHANGING SLOPES
J. A. Heydenreich1, R. L. Mickol1, J. C. Dixon1,2, V. F. Chevrier1 and T.A. Kral1,3
Recurring slope lineae (RSLs) are dark streaks that appear on
the martian surface annually. They are hypothesized to be
formed from liquid brine flowing downslope in the subsurface.
Emerging from bedrock, RSLs occur on steep slopes during the
warm spring-summer months and fade when the
temperatures decrease in the winter. Gullies commonly
emerge from bedrock and form from volatile melting and
associated sediment accumulation. All of these forms involve
the movement of fluids and associated sediments on variable
slopes [1]. The objective is to generate flows at slope ranges
that represent those on which RSLs and gullies occur on Mars.
1. Dry Debris Flows: Dry granular flows and rock falls
2. Adsorbed Water: Released at high temperatures creating
dry mass wasting
3. Subsurface Flows: Liquid brines underneath the regolith
4. CO2 Sublimation: CO2 frost triggers mass movement [1, 2]
42.8cm56.8cm
Brines
• Lower the freezing
point
• Create ‘wet’ slope
streaks
• Warm temperatures
would exceed the
eutectic
temperature of salt
water melting the
frozen brine
underneath the
surface
• MgCl2, NaCl or CaCl2
brine compositions
[3]
RESULTS
The lower slopes relate more closely to RSLs from their basic
fluvial geomorphology features. Higher slopes produce more
distinct morphologies associated with fluvial erosion that are
more similar to gullies. The effect of viscosity could also alter the
morphologies of the flow features.
[1] McEwen, A. S. et al. (2011) Science 333, 740-743. [2] Dundas, C.M., McEwen,
A.S., Diniega, S., Byrne, S., Martinez-Alonso, S., 2010. New and recent gully
activity on Mars as seen by HiRISE. Geophys. Res. Lett. 37, L07202. [3] Chevrier,
V.F., Rivera-Valentin, E.G., 2012. Formation of recurring slope lineae by liquid
brines on present-day Mars. Geophys. Res. Lett. 39, L21202.
The width of channels decreased with increasing slopes of the
flume. The channel lengths increased with the increasing slopes.
Greater slopes produced channels with more variability in
geomorphic features.
OBSERVATIONS
Figure 2: (A) The higher slopes produced channels with more variability in features such as
diverging lobes and natural levees commonly associated with natural gullies. (B) The lower
slopes produced more basic, dendritic channels more closely related to RSL formations.
Figure 3: The alcove length stayed relatively constant. The total and apron length has a
significant increase when the slope increased. The maximum width, the saturated zone
adjacent the channel, decreased as the slope increase.
Future work will investigate the difference between regolith
simulants (sand, Mojave Mars Simulant), use Natrosol to adjust
the fluid viscosity and compare environmental conditions with
different temperatures (room temperature, -20 °C).
FUTURE WORK
Filled a 0.67 m x 0.51 m wooden flume with 8 kg of JSC Mars-
1, giving a bulk density of 1.02 ± 0.02 g/cm3. Slopes were set
by adjusting flume height. Water flowed through tubing
connected to a copper pipe centered at top of flume just
beneath surface of regolith for 15 to 25 seconds. After, total
channel, apron and alcove length were measured.
METHODS
INTRODUCTION
1Arkansas Center for Space and Planetary Sciences, 346 ½ N. Arkansas Ave., University of Arkansas, Fayetteville, Arkansas 72701
2Dept. of Geological Sciences, 113 Ozark Hall, University of Arkansas, Fayetteville, Arkansas, 72701
3Dept. of Biological Sciences, 601 Science and Engineering Building, University of Arkansas, Fayetteville, Arkansas, 72701
CONCLUSION
0
10
20
30
40
50
60
70
80
10 12 14 16 18 20 22 24 26 28 30
Length(cm)
Slope (degrees)
Total Length
Alcove Length
Apron Length
A B
Figure 4: As the slope increases the total and apron length increase. The alcove
length stays relatively constant throughout the different slope angles.
FLOW FORMATION HYPOTHESES
Figure 1: (A) shows dark streaks appearing in Late
Summer, fading in (B) and (C) in the following year
Early Spring and (D) reappearing in Early Summer [1].
0
10
20
30
40
50
60
70
80
Alcove Length Total Length Apron Length Max Width
Length(cm)
Channel Attribute
12° 15° 18° 25° 30°
HIGHER SLOPE LOWER SLOPE
SUBSURFACE FLOWS