1. Experimental Simulations of Recurring Slope Lineae
J. A. Heydenreich1, J. C. Dixon1,2 and V. F. Chevrier1
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 under regolith
4. CO2 Sublimation: CO2 frost triggers mass
movement [1, 2]
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
• Lower slopes relate more closely to RSLs from their
basic fluvial geomorphology
• Higher slopes produce more distinct morphologies
associated with fluvial erosion that are more similar
to gullies
• Colder temperatures altered the channel attributes,
longer total channel and apron lengths
• Saturated salt solutions, like the brine subsurface
flows, increased the total channel and apron lengths
• 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., et al. (2010) Geophys. Res. Lett. 37, L07202. [3] Chevrier, V.F.
and Rivera-Valentin, E.G. (2012) Geophys. Res. Lett. 39, L21202.
Figure 2: Lower slopes (A) & (B) produced more basic, dendritic channels more
closely related to RSL formations. Higher slopes (C) & (D) produced channels with
more variability in features such as diverging lobes and natural levees commonly
associated with natural gullies. Cold temperatures produced longer channels (B) &
(D).
Figure 3: The measurements of the channel attributes from experiments conducted
in a freezer cold room (-20 °C) and room temperature (21 °C) at 10°, 20° and 30°
slope angles with pure water.
Future work will investigate the difference between
regolith simulants (sand, Mojave Mars Simulant) and
use Natrosol to adjust the fluid viscosity.
FUTURE WORKFilled 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 of 10, 20 and 30 degrees were set by adjusting
flume height. ~100 mL of water or salt-saturated water
was funneled through tubing connected to a copper
pipe centered at the top of the flume, just beneath the
regolith surface. After each run, total channel, apron,
and alcove length, maximum width and maximum
elevation were measured. Experiments were conducted
at room temperature (21 °C) and at -20 °C.
METHODS
INTRODUCTION
1Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, Arkansas 72701
2Dept. of Geological Sciences, University of Arkansas, Fayetteville, Arkansas, 72701
CONCLUSION
Figure 4: The 20° slope experiments recreated in a freezer cold room (-
20 °C) and room temperature (21 °C) with saturated salt water (NaCl +
pure water).
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].
SUBSURFACE FLOWS
REFERENCES
ROOM TEMPERATURE COLD TEMPERATURE
A B
C D
36 cm32.8 cm
41.7 cm39.7 cm
0
10
20
30
40
50
60
Alcove Length (cm) Total Channel
Length (cm)
Apron Length (cm) Max Width (cm) Max Elevation (mm)
Length
Channel Attributes
10° Slope Cold
10° Slope Room
20° Slope Cold
20° Slope Room
30° Slope Cold
30° Slope Room
• Alcove lengths stayed relatively constant throughout
all experiments
• Total channel and apron lengths increased with the
increasing slopes
• The maximum channel width decreased with
increasing slopes
• Maximum elevation of the channel’s terminal lobes
increased with increasing slopes, due to sediment
erosion and transport
• Greater slopes produced channels with more
variability in geomorphic features
OBSERVATIONS
0
10
20
30
40
50
60
Alcove Length
(cm)
Total Channel
Length (cm)
Apron Length
(cm)
Max Width (cm) Max Elevation
(mm)
Length
Channel Attributes
20° Slope Cold
20° Slope Room
20° Slope Cold NaCl
20° Slope Room NaCl