ON SCIENTIFIC GOALS OF THE SEISMIC EXPERIMENT “MISS”
T. Gudkova1, P. Lognonné 2, V.N. Zharkov1,
S. Raevskiy1, V. Soloviev1 and “MISS”
team1,2,3,4.
Schmidt Institute of Physics of the Earth, Russia;
2 Institut de Physique du Globe de Paris, France.
3 Institute of Space Research, Russia
4 Moscow Institute of Physics and Technology, Russia
1
Contact: gudkova@ifz.ru
Our present knowledge on the bulk composition and interior structure
of Mars is based on geophysical and geochemical information and
high-pressure experiments
Geophysical constraints
 The mass and the mean radius of the planet M=6.4185x1023 kg, R=3389.92 km
 The value for the mean moment inertia (obtained from the measurements of the precession rate of the
planet by the Pathfinder mission and the MGS mission)
0.3647-0.3663 (Konoplive et al., 2006)
 The inferred elastic Love number (obtained from the gravity analysis of orbiting spacecrafts)
k2=0.148±0.0.009 (Konoplive et al., 2006)
k2=0.11
(Marty et al., 2008)
k2=0.156±0.0.009 (Konoplive et al., 2011)
Chemical composition (based on the analyses of the composition of Martian meteorites)
►The cosmochemical DW model (Dreibus, Wänke, 1989; Wänke, Dreibus, 1994)
A:B=60:40
Fe/Si=1.71
Fe#=0.25 (Fe#=Fe/(Fe+Mg)x100)
► Sanloup et al., 1999 to match the δ17O/ δ18O ratio 55% ordinary chondrite H and
► Lodders, Fegley, 1997
Lodders, 2000
45% enstatite chondrite EH
85% H chondrite
11% CV chondrite
4% C1 chondrote
High-pressure experiments
 a model of the mantle - high-pressure experiments with an analog of the DW composition up to
core-mantle boundary pressures along a model areotherm (Bertka, Fei, 1997, 1998)
 for the model of the core - experimental data of high PT phases of -Fe and FeS (Kavner et al 2001)
Model estimates of the elastic Love number k2 versus core radius
for the models consistent with the mean moment of inertia
k2s=0.145±0.017 ,
Rcore = 1520-1840 km
k2s=0.148±0.009 (dashed lines), Rcore = 1600-1810 km
k2s=0.156±0.009 (solid lines),
Rcore = 1770-1830 km
Yoder et al., 2003
Konoplive et al., 2006
Konoplive et al., 2011
Rcore = 1700 - 1800 km
k 2s
0.18
The presence of a perovskite-bearing lower mantle ?
a
0.16
0.14
0.12
0.1
1600
1700
1800
Core radius, km
1900
► Love number k2 =0.148 (Konoplive et al., 2006)
k2 =0.156 (Konoplive et al., 2011) 
1) lower mantle becomes impossible
2) the mantle is softer than the assumed elastic solid mantle
because of partial melt at depth (Yoder et al.,2003). This
would have the effect of reducing the inferred core radius
by 100-150 km.
► Love number k2 =0.11 (Marty et al., 2008) allows smaller
core and,hence, the presence of perovskite bearing lower
mantle
The determination of the core size is a key objective for seismology
Seismology is the best tool for
probing planetary interiors.
• Body waves
• Surface waves
• Free oscillations
How a single seismometer can be useful to get information on
subsurface structure and average global structure of the planet?
Nontraditional ways to probe the interiors should be used:
 data processing of meteoroids’ impacts,
 seismic hum from meteorological forcing,
 the development of new methods, that can derive interior
information from a single seismometer.
Many such methods already exist:
 source location through P-S and back-azimuth,
 receiver functions,
 identification of later phases (PcP, PKP, etc),
 surface wave dispersion,
 normal mode analysis (from single large events, stacked events, or background noise).
What can be determined:
1) Mars’ seismicity level
2) The crustal and upper mantle structure:
meteoroid’ impacts
the dispersion curves of surface waves
receiver function method
free oscillations
3) Some restrictions on the seismic velocities in the deep mantle
differential measurements of arrival times of later-arriving phases (PcP, PcS, ScS) in comparison
to P
The first goal of the experiment is determining Mars’ seismicity level
No past missions have returned seismic information on the Martian interiors.
By theoretical estimates Mars is assumed to be seismically more active than the Moon but less active than the Earth.
may be expected per year (Phillips and Grimm, 1991;
Solomon et al., 1991; Golombek et al., 2002, Knapmeyer et al., 2006)
more than 10 events of seismic moment greater than 1023 dyne cm,
more than 250 events of magnitude greater than 1021 dyne cm,
a few (2-3) should have a moment greater than 1024 dyne cm.
a 1025 dyne cm quake is the upper bound of the estimate of the
activity on Mars
Seismicity map (Knapmeyer et al., 2006)
The quakes are related to the thermoelastic cooling of the lithosphere, which accumulates stresses
that are then released by quakes. This type of activity is the minimum expected activity on Mars.
Taking into account the fact that one can see giant faults on the surface of Mars (within Tharsis
region, Tempe Terra, Valles Marineris, Olimpus region), it is not possible apriori to rule out large
seismic events.
Meteoroid impacts



an additional and very important seismic sources for a planet with a weak
atmosphere for constraining the crustal and upper mantle structure
the number of impacts are expected to be 2-4 times larger then for the Moon
their impact time and location can be known with orbital imaging
(high-resolution cameras is on orbiting Mars spacecraft)
Both P and S arrival time can be used on a seismometer. If the time is not known,
the P-S differential travel-times can be used.
The main characteristics of the seismic source
generated by an impact are its amplitude and
cutoff frequency. These parameters allow us to
constrain the mass and velocity of the impactor.
The larger an impact is, the lower is its cutoff
frequency.
Free oscillations
Free oscillations, if they are excited,
are particularly attractive to probe
beneath the surface of an
extraterrestrial body into its deep
interior.
Interpretation of data on free
oscillations does not require
knowledge of the time or location of
the source; thus, data from a single
station are sufficient.
Since the planet has finite dimensions and is bounded by a free surface, the study of the free
oscillations is based on the theory of vibration of an elastic sphere. The planet reacts to a
quake (or an impact) by vibrating as a whole, vibrations being the sum of an infinite number
of modes that correspond to a set of frequencies.
Can the free oscillation method be used to study Martian interiors?
Current broad band seismometers can measure
accelerations (Lognonné et al., 1996)
a N,E= - 2 uN,E ≈ 10-8 cm/s2,
a N,E - the ground acceleration, uN,E - the
ground displacement in the North and East
direction.
Torsional oscillations:
M0=1025 dyn cm: l3 (up to 1600 km)
M0=1024dyn cm: l6 (up to 1100 km)
M0=1023dyn cm: l12 (up to 700 km)
Spheroidal oscillations:
M0=1025 dyn cm: l17 (up to 700-800 km)
M0=1026dyn cm: l6 (up to 2000 km)
Functions 0Ul proportional to the displacements for spheroidal
oscillations for the fundamental mode, l=2 to 10 vesus relative
radius r/R. 0Ul is normalized to unity at the surface.
The fundamental modes sound to those depth in the
interiors where its displacement  0.3
The horizontal line drawn at level =0.3 enables one to
judge graphically which modes give information about
one or another zone of the planet.
The dispersion curves of surface waves can be used to solve problem of determining
the structure of the crust and the upper mantle
The depth to which surface waves are sensitive depends on frequency, with low frequency waves feeling to
greater depth and therfore propagating with higher speeds. Low frequency waves are arriving earlier than
higher frequencies. They are extremely sensitive to subsurface structure (to the crustal thickness).
The velocity can be calculated from arrival time and estimate of distance from the source, which can be
obtained from R1-R2 difference, where R1 is the direct Rayleigh wave arrival, R2 is the arrival of the wave
propagating around the planet in the opposite direction.
MK2L
3.4
Density
,
g/cm3
3.5
MK2M
3.3
4.2
Group velocity oUn, km/s
The data on Rayleigh waves enable one to distinguish between not
only the crusts with different composition (MK2M and MK1M), but
also between the models based on different temperature
distribution in the crust (MK2M, MK2H and MK2L).
4.0
1
2
3
4
3.8
3.6
MK1M
MK2H
3.2
0
50
3.4
100
Depth, km
150
0
50
100
150
Period T, s
200
Profiles of density in the different models of the Martian crust (MK1M, MK2M, MK2H and MK2L) are on the left (the
data are from (Babeiko A. et al., 1993)) and group velocities oUn for a fundamental mode of Rayleigh waves as
function of the period of oscillation for these models: 1, MK2L; 2, MK2M; 2, MK2H; 4, MK1M.
250
BODY WAVES
Differential measurements of arrival times of later-arriving phases (PcP, PcS, ScS) in
comparison to P could put some restrictions on the seismic velocities in the deep mantle.
Synthetic seismogram analysis for interoir structure models can lead to its identification.
400
SKS
Travel-time differences T(s)
300
PKP
The difference are
up to 40 s for P and PcP , and
up to 100 s for S and ScS arrivels.
PcP and ScS, phases reflected from the core, could provide a
strong constraint on the core’s radius.
For diagnostic purposes, the core phases PKP and SKS are
the most promising phases in Martian seismology.
The difference between models are about 300-350 s.
200
S
100
ScS
P
PcP
0
8
40
80
120
6
160
Epicentral distance (km)
Travel times P, PKP, PcP, S, SKS, ScS waves difference between a trial
model M7_3 (Zharkov et al., 2009) (Rc=1766 km; the density of 50-km thick
crust is 3000 kg/m3) and the model A (Rc=1468 km; the density of 110-km
thick crust is 2810 kg/m3) of (Sohl, Spohn, 1997):
solid line - the source is on the surface
dashed line - the source is at the depth of 300 km.
density, g/cm3
0
4
2
0
0
0.2
0.4
0.6
relative radius r/R
0.8
1
We have showed the mission possibility to get
seismic information on Martian interiors from only
one seismic instrument using non-traditional
sources of seismic waves and new seismic
techniques.
Very Broad Band seismometer will record the full
range of seismic signals, from the expected
quakes induced by the thermoelastic cooling of the
lithosphere, to the possible permanent excitation of
the normal modes. All these seismic signals will be
able to constrain the structure of Mars’ interiors.