Some Thoughts About Rock Mechanics Aspects of Mars
Ömer Aydan
University of the Ryukyus, Department of Civil Engineering
Nishihara, Okinawa, Japan
3rd Off Earth Mining Forum - 2017OEMF
Opportunity Curiosity Spirit
Courtesy of NASA
1) Motivation
2) General Characteristics of Mars
3) Surface Topography and Geology
4) Tectonics and Seismicity
5) Stress State of Mars
6) Rocks
7) Formation of Discontinuities and Their Surface Morphology
8) Rock Weathering
9) Slope Stability Problems
10) Sinkholes
11) Properties of Rocks, Discontinuities and Rock Masses
12) Conclusions
Acknowledgements
Contents
1) Motivation
Mankind is now exploring the ways
to find out the characteristics of
other planets and possibility of
exploiting their mineral resources..
One of most impressive images
from the Apollo Program of NASA
to me is the man standing next to a
fractured lunar rock mass.
The images from recent Mars exploration rovers showed the
striking similarities between rocks on Earth and those of Mars,
which motivated me to bring together some of my thoughts
about the aspects of rock mechanics and rock engineering in
Mars and to compare them with those of the earth.
In this presentation, I will specifically consider the stress state,
the characteristics of rocks and their weathering, discontinuity
formations, slope and cliff stability problems and natural caves.
Teaching Rock Mechanics and Rock Engineering in Space in my
Rock Mechanics Classes in Tokai University since 2010 and
University of the Ryukyus since 2014
(Rock Mechanics in Other Planets)
(Contents)
2) General Characteristics of Mars
Gravitational acceleration is 0.377g of the Earth
Radius is 3389 km
Mean density is 3.933 g/cm3
c) TEMPERATURE VARIATIONS
Temperature difference is more than 80 degrees
Subjected to Harsh Freezing and Thawing Environment provided rock is saturated
From NASA
Earth is 20-40 degrees
LARGE SCALE SHEARING, FAULTING, FOLDING AND ASSOCIATED
METAMORPHISM
FAULTING SHEARING & FAULTING
FAULTING, FOLDING & METAMORPHISM
Sedimentation and Tilting Sedimentation and Discordance
Volcanic Activity & Columnar Jointing Folding and metamorphism
Mars-quakes (?)
No Doubt that Mars-quakes should exist as it happens in Moon Possible Causes of Quakes
a) Impacts by Meteorites
b) Thermal Contraction & Expansion
c) Volcanic Activity
d) Large Scale Mass Movements
e) Plate-tectonic Type Movements
f) Daily Rotation and Annual Solar Motion
InSighter Module
No Instrumentation yet
0 100 200 30029
30
31
5.6
5.8
6.0
6.2
TIME (DAYS)
VE
LO
CIT
Y (
km
/s)
AC
CE
LE
RA
TIO
N (
mm
/s2)VELOCITY AND ACCELERATION OF EARTH
Acceleration Velocity
5) Stress State of Earth & Mars
s1 = s3 + S¥ - (S¥ -s c )e-b1s3é
ëùûe
-b2T
Case 1: Hydrostatic-fluid
Case 2: Mantle-crust are elastic & solid; core fluid
Case 4: Same condition as above, thermo-plasticity
Tan. Stress Max, All Compressive:
6.3 GPa at surface.
Basalt UCS is 0.6 GPa
Upper Mantle is in plastic
state. This was the main
cause of tectonics in
Earth
• Overcoring Method
• Stress Relief & Restoration Method (Flat jack Method)
• Hydraulic Fracturing Method
• Sleeve Fracturing Method
• Acoustic Emission Method (AEM)
Compiled by Aydan and Kawamoto, 1998
Direct Techniques
InDirect Techniques
• Borehole-breakout Method
• Fault-Striation Method
• Focal Mechanism Solution Method
• Blasthole Damage Method
Stress State of Mars Constitutive Law and
Thermo-plastic yielding
characteristics are
needed
Proper evaluation of stress state of Mars will enable us to explain
Why mountains are high and
Why tectonism is less pronounced in Mars
Earth Mars
7) Discontinuities
i) Tension discontinuities due to
- Cooling
- Drying
- Freezing
- Bending
- Flexural slip
- Uplifting
- Faulting, and
- Stress relaxation due to erosion or glacier retreation
or man-made excavation
ii) Shear discontinuities due to
- Folding, and
- Faulting
iii) Discontinuities due to periodic sedimentation, and
iv) Discontinuities due to metamorphism.
Characterization of rock mass depends upon, intact rocks,
discontinuities, weathering state etc.
SURFACE MORPHOLOGY OF DISCONTINUITIES
Shear strength of discontinuities are greatly affected
by their surface morphology parameters
Rover’s Vibration Induced Mass Movements
Some wrongly interpreted as the motion was caused
by fluid flow, liquefaction etc.
Before
After
Motion of dry granular deposits before and
after shaking
From Aydan & Ulusay (unpublished 2000)
10 20 30 40 50
10
20
-1000
0
1000
0
TIME (sec)
SE
TT
LE
ME
NT
(m
m)
CU
MU
LA
TIV
E A
E C
OU
NT
(x 1
0)
BA
SE
AC
CE
LE
RA
TIO
N (
gal)Sand4- dry1
Travel length: 675 cm
Inclination: 23.5 degrees
Maximum Acceleration: 42.13 cm/s2
Maximum Velocity: 238.5 cm/s
Basalt friction angle: >30 degrees
)tan( m
gaMaximum Acceleration
)tan(2max
m
gv
Maximum Velocity
SOME INFERENCES FROM SLIDING OF BLOCKS
0 10 20 30-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
TIME(sec)
FR
ICT
ION
CO
EF
FIC
IEN
T(S
/N)
NO
RM
ALIZ
ED
AC
CE
LE
RA
TIO
N(a
/g)
S/N
Upper Block Acceleration
Mt.Fuji Basalt Saw-cut Surface
12) Conclusions
The rock mechanics aspects of Mars are quite similar to
those of the Earth.
The differences result from gravitational acceleration,
climatic conditions (temperature, humidity, winds),
thickness of atmosphere and non or limited amount of
ground water.
The knowledge on the behaviour of rocks, discontinuities
and rock masses acquired on the Earth can be easily
used in Mars with the consideration of the differences
resulting from gravitation acceleration, climatic conditions
and fluid in rock masses.
The author heart-fully thanks the organizing committee and
the invitation to join the 2017 Off-Earth Mining Forum and to
have chance to address you on my thoughts.
The author gratefully acknowledges NASA and the people
involved in the development and operation of Mars exploration
programs, Mars rovers, namely, Opportunity, Sprit and
Curiosity, and processing and releasing their images on
related web-sites.
The author is solely responsible for the content, statements
and opinions made in this presentation
ACKNOWLEDGEMENTS
Thoughts of the author are based on Images of Mars Rovers and
mostly obtained from the following web-site:
https://mars.nasa.gov/mer/gallery/images.html
THEMES
■ Laboratory tests on Dynamic Responses of Rocks and Rock
Masses; Fracturing of Rocks and Associated Strong Motions
■ Estimation Procedures and Numerical techniques of Strong
Motions Associated with the Rupture of Earth’s Crusts and Some
Strong Motion
■ Dynamic Response and Stability of Rock Foundations,
Underground Excavations in Rock, Rock Slopes Dynamic
Responses and Stability of Stone Masonry Historical Structures
and Monuments
■ Induced Seismicity
■ Dynamic Simulation of Loading and Excavation
■ Rockburst and Outburst
■ Blasting
■ Impacts
■ Nondestructive Testing Using Shock Waves
■ Case Histories of Failure Phenomenon in Rock Engineering
■ Rock Dynamics in Space