Network Science
Netlander: a European mission to study the planet Mars.
Veronique Dehant*, Philippe Lognonné**, and Christophe Sotin***
*Royal Observatory of Belgium
**Institut de Physique du Globe de Paris, France
***University of Nantes, France
With the participation of the whole NetLander team:
Jean-Pierre Barriot, Jean-Jacques Berthelier, Jean-Louis Counil, Greg Delory, Ralf
Jaumann, Ari-Matti Harri, Michel Menvielle, Tilman Spohn.
The planet Mars has many Earth like characteristics, but its evolution is different.
An important future step in Mars’ geophysics is to deploy a network of stations at the
surface of Mars in order to study a wide range of properties of this planet, going from its
deep interior structure to its atmosphere. Each ground station (small landers) will
contain the same scientific instruments/experiments. The collected data will improve our
knowledge of the Martian interior, surface and atmosphere, as well as its evolution. An
important part of these objectives can only be achieved by a network of surface stations,
as a network gives unique possibilities for performing studies of global scale phenomena
and studies requiring simultaneous measurements from several sites.
Introduction
Many questions concerning Mars are already addressed by the past and present
mission to Mars (e.g. Viking (launched in 1975), Pathfinder (1996), Mars Global
Surveyor (1997), Mars Odyssey (2001), Mars Express (2003), Mars Exploration Rovers
(2003), Mars Reconnaissance Orbiter (2005)…). But complementary to these missions,
questions addressing the global dynamics and circulation in the atmosphere, the detailed
crust, sub-surface, lithosphere, mantle, and deep interior structures, and the related
dynamics cannot be addressed by these missions. The most important part of these
objectives can only be reached by network science, i.e. to deploy a network of
instruments on the Martian surface. This is for instance the case of rotation study,
seismology, meteorology, or electromagnetic sounding. The idea is to study the same
physical process at different sites in order to understand global phenomena.
A network mission will be a major step in our understanding of the history and the
present state of Mars. Our current knowledge of the internal structure of the planet is very
limited and is mainly based on observations of its gravity field (using the orbit of the
spacecraft around Mars, one can reconstruct the gravity field and its time variation; in
particular the tidal effects could be observed and provided information on the interior of
Mars as shown by Yoder et al., 2003), and on the chemical analysis of some meteorites
found on Earth that originate from Mars. The idea is to deploy a few identical small
stations (see Figure 1) on the surface of Mars and to perform geophysical measurements
for at least one Martian year (equivalent to about two terrestrial years). A relay satellite in
orbit around the planet will collect and transmit the data from the small stations to the
Earth. This was the idea of the previously foreseen NetLander mission (Lognonné et al.,
1999, Harri et al., 1999), which has went until a full phase B in 2003 before its
cancellation for budget reasons by both the French and US Space agencies.
Figure 1: Representation of a Netlander station.
A network of stations gives unique possibilities for performing studies of global scale
phenomena and studies requiring simultaneous measurements from several sites and was
already studied several times in Europe in the 1990’th with the ESA Marsnet (Chicaro et
al., 1993) and ESA/NASA InterMarsnet projects (Banerdt et al.,1996) all stopped after
phase A. The objectives of a network science mission are to study:
– the deep internal structure of the planet,
– Mars’ rotation,
– the subsurface structure, down and below the liquid water rich layers,
– the surface-atmosphere interactions and the global circulation of the atmosphere,
– the geology of the landing sites,
– the electromagnetic environment of the surface, and
– the ionospheric activity.
Nine instruments have been selected for the phase A and B of the NetLander mission and
were described in a special issue of Planetary and Space Science (Sotin et al., 2000).
These instruments and the countries that are in charge of the development or feasibility
studies of these instruments are shown on Figure 2. The thermal and mechanical
mockups of the station have already been developed by DLR (see Figure 3).
ARES
PANCAM
MIC
ATMIS
MAGNET
NEIGE
GP
R
SEIS
SPICE
GPR
Figure 2: The NetLander experiments and the countries involved.
Figure 3: Lander mockup of the NetLander mission.
Network mission scientific aims
More generally, a network of landers will gather invaluable information on the deep
internal structure of Mars, the global atmospheric circulation, the subsurface structure,
and the geology of the Martian surface. The different experiments that could be included
in the small geophysical stations will be described in details below. We will review first
the main achievements foreseen by a network mission in the frame of the Martian
geophysics.
Mars internal evolution and structure
By using geodesy, seismology and magnetism experiments, Mars’s interior will be
studied. The determination of the size and state (liquid or solid) of the core and of the
structure of the mantle are questions of primary importance. We already know from the
interpretation of the secular acceleration of Phobos (e.g. Lognonné and Mosser, 1993)
and from the detailed analysis of the tracking of Pathfinder and MGS that Mars’ core is
most probably liquid (Yoder et al., 2003), but this would need a confirmation and precise
determination of the core-mantle boundary depth. The possible existence of an inner core
within the liquid core is also a question to be addressed.
The NEIGE geodesy data will give information on the interior properties. In particular,
the planet’s rotation will give information about the Martian materials, their state
(solid/liquid), their dimensions, and their densities (Dehant et al., 2000). As for the
Earth, the position of Mars’ rotation axis varies with time due to the gravitational
attraction exerted by the Sun and the Mars’ natural satellites Phobos and Deimos.
Because of the existence of an equatorial bulge (like the Earth, Mars is flattened at the
poles, but the flattening of Mars is about 0.005 less than the one of the Earth of about
0.003), the Sun’s attraction continuously tends to tilt Mars’ equatorial plane towards the
orbital plane. The rotating Mars reacts to this force as a gyroscope, and the Mars’ rotation
axis describes a broad cone around the perpendicular to the orbital plane. This forced
motion is called precession. Because the relative positions of the Sun, Mars, Phobos, and
Deimos periodically change with time, precession also shows periodic variations, called
nutations (see Figure 4), of which the amplitudes are maximum 10 meters at the surface
of Mars (the largest nutation has an amplitude of about 500 milliarcseconds or 8 meters at
the surface of Mars, for the prograde annual nutation).
Figure 4: Schematic representation of the rotation, precession and nutation of Mars.
The internal structure of Mars influences the nutations; in particular a resonance effect in
the nutations could be seen if Mars has a liquid core. Such a resonance implies that some
nutations could be largely amplified. If the existence of this resonance is deduced from
the NEIGE data, it would prove that the Martian core is at least partially liquid (see
Figure 5).
rigid Mars’ nutations
250 days
transfer function
250 days
non-rigid Mars’ nutations
250 days
Figure 5: Schematic representation of the amplification of the nutations due to the liquid
core resonance.
On the Earth, most of the internal structure was determined by seismic studies, which
started at the end of the 19h century. One century latter, the state-of-the-art consists of 3D
models of the Earth mantle. Seismic 1D imaging was also applied to the Moon (e.g.
Nakamura et al., 1976, Lognonné et al., 2003), although the very deep structure remains
unknown, due to the non-detection of large epicentral distance quakes by the Apollo
seismic network. For a general review on planetary seismology, see Lognonné and
Mosser (1993).
Mars is unfortunately a seismically unexplored planet and the two previous
attempt to perform a seismic reconnaissance (i.e. detection of Marsquake) have failed,
either for Viking (Anderson et al, 1977) or for the Mars96 mission (Lognonné et al,
1998). The seismic data (SEIS experiment) will give information on the density of
materials constituting the crust, the mantle and the core as well as on the elastic
properties of these parts. A detailed description of the scientific objectives and
expectations of a seismic experiment on Mars are given by Lognonné et al. (1996, 2000,
2003), supplemental data on the electric resistivity of the underground will be measured
by the magnetometer (MAGNet).
It is possible to realize a synergy between SEIS, NEIGE and MAGNet. A probabilistic
approach has been recently used in order to deduce the mineralogy and the temperature
profiles from the data of the three experiments (Verhoeven et al., 2004).
Martian meteorology
At each of the sites, the ATMIS atmospheric sensors will measure various meteorological
parameters such as the pressure, the temperature, the humidity, the wind speed and
direction, the optical thickness (opacity of the atmosphere). The measurement of the
length of day variations by the NEIGE experiment will be a key indicator of the global
circulation of the Martian atmosphere. These variations are mainly related to the
exchanges of matter between the atmosphere and the polar ice caps. In addition, the study
of the atmospheric electric field (ARES) will provide information on the atmosphere and
surface compositions, and on the mechanisms that trigger dust storms in the atmosphere.
Subsurface structure
An important objective will be the search for ground reservoirs of water, either as ice or
as liquid water, in as much this question is essential to understand the long-term
evolution of the atmosphere of the planet and of its climate. Present models of the
thermal flux suggest that liquid water should be encountered at depths of 1 km near the
equator increasing to 3 to 5 km in the polar regions. These levels, as well as the
characteristics of the more superficial ice – such as its rheology or its ability to diffuse
through the regolith – are most probably also subject to seasonal changes.
The study of the subsurface, including the permafrost, will be actively performed with a
geo-radar, and passively with the magnetometer and seismometer. A Ground Penetrating
Radar (GPR) will probe the subsurface down to depths of the order of ~ 2 km to search
for signatures of ice reservoirs and possible transition to liquid water layers.
Simultaneously radar data will give access to the main structural and geomorphological
features of the subsurface. The GPR will carry out surveys of the upper layers of the
Martian underground up to a depth of a few kilometers and will be able to detect the
presence of liquid water below the stations, if any.
Geology of surface
The geology and the mineralogy of the landing sites will be investigated with the
PANCAM panoramic camera.
Importance of comparative planetology
Mars is a very interesting planet for the study of the formation and evolution of
terrestrial planets, to which the Earth, Mars, Venus and Mercury belong. Mars is
somewhat smaller than the Earth with a diameter about half that of the Earth, but has a
similar chemical and mineralogical composition, and its global internal structure, with an
iron core, a mantle and a crust, is such as for the Earth. Soon after their formation, the
Earth and Mars must have been very alike. Nowadays, the neighbouring planets show
many differences. For example, Mars has a tenuous atmosphere with almost no oxygen.
Its surface is very dry without liquid water and has been created long time ago, in
contrast to the Earth’s surface, which is continuously recycled through tectonic motions.
Volcanism activities and earthquakes on Mars are almost extinct. This indicates that both
planets differ internally. The Earth is a dynamic planet, with large-scale motions in its
core, mantle and crust. Mars, on the other hand, is a calm, “dead” planet. It is very
interesting to investigate how and why Mars differs from the Earth. For example,
although it is known that Mars has a core consisting mainly of iron, the dimension and
the precise composition of this core remain unknown. Moreover, the present geodesic
data have allowed to favor a liquid core (Yoder et al., 2003). However, no other
definitive proof of the liquid core has yet been derived. A future network mission on
Mars will allow us to confirm that the core is liquid, and to determine whether, such as
for the Earth, it has a central solid part surrounded by liquid layers, or would be
completelyliquid. Answers to these questions are very important for a better
understanding of the formation and evolution of Mars and terrestrial planets in general,
and could yield more insight into the future of these planets.
Some characteristics of Mars
Climate data
Because of its greater distance from the Sun, Mars receives less solar energy than the
Earth. Moreover, the greenhouse effect on its surface is less significant. Its annual
average temperature is therefore lower, about -53°C, compared to +14°C for the Earth,
and minima and maxima are about -125°C to +23°C. The planet experiences moreover
significant daily thermal variations, which can be explained by the lack of oceans and by
the tenuity of its atmosphere. At the Martian surface, the vertical gradient of the
temperature is very significant, at the level of 20°C per meter and the temperature scale
height varies very rapidly.
An important characteristic of Mars’ atmosphere lies in the mass exchange with
the polar caps. The central parts of these caps are made of water ice, covered during
winter with a layer of carbon dioxide (CO2). The size of these caps shows large seasonal
variations. During the Martian winter, their increase is due to the condensation of
atmospheric carbon dioxide. In summer, their decrease is due to the sublimation of this
carbon dioxide, which then returns to the atmosphere.
Geodesy data
Mars revolves on an elliptical orbit at an average distance of about 228 million kilometers
from the Sun. Its equatorial diameter is about half of the Earth’s one and its mass about
ten times smaller. One Martian year (period of revolution around the Sun) is
approximately equal to two terrestrial years (687 days), and the average duration of the
Martian day (period of the rotation of the planet on itself) is 24 h 37 m. The moment of
inertia of the planet has been determined from radio-science experiments using Doppler
and range measurements of Viking and Pathfinder data (Folkner at al., 1997).
Magnetic data
The magnetic field is an important parameter for the understanding of the evolution of a
terrestrial planet. The presence of a global magnetic field is related to the existence of
motions in the liquid iron core. The cooling of Mars as well as its chemical composition
determine whether the core is liquid or solid. Contrary to the Earth, no significant global
magnetic field has been observed for Mars. However, the Mars Global Surveyor satellite
highlighted the presence of a significant local magnetic field at some places of the planet.
Network mission scientific instruments
Each lander will contain the same scientific instruments; in the case of NetLander, nine
experiments were foreseen, which are briefly described below.
Magnetometer (MAGNet)
The MAGNet experiment is based upon continuous recordings of the magnetic variations
at a network of stations installed at the Mars surface, by means of three-axis
magnetometers placed on the Martian soil (Menvielle et al., 2000). A magnetometer is a
device primarily conceived for measuring magnetic fields. But the objectives of the
MAGNet experiment are twofold: to investigate the vertical structure of Mars to depths
of a few hundred kilometers from electrical conductivity, and to characterize the
electrodynamics of the Mars environment. This could only be done for a network of
instruments.
The electromagnetic sounding techniques are based upon the estimation and
analysis of the impedance, which characterizes the inductive response of the conductive
planet. This response is related first to the inducing primary field, i.e. the transient
magnetic field of external origin, which is the magnetic signature of the plasma flow and
current in the ionized environment; secondly it is related to the induced field of internal
origin depending on time and space characteristics of the external field, and on the
distribution of electrical resistivity inside the planet.
The Mars electric structure is estimated through the analysis of the inductive
response of the planet by means of electromagnetic sounding techniques at high and low
frequencies (Pinçon et al., 2000). This inductive response is estimated from simultaneous
magnetic recordings of a network of three stations. The high frequency spectrum of the
transient variations provides information on the resistivity in the uppermost kilometers of
the planet, and then on the presence (or absence) of liquid water under the permafrost.
The low frequency spectrum of the transient variations give information on the presence
(or absence) of sharp variations in the resistivity in the uppermost hundreds of kilometers
of Mars, and thus on the thermodynamic conditions within the upper mantle of the planet.
As in the case for the Earth, different possible controlling plasma processes will
lead to different convection patterns inside the magnetosphere and therefore different
magnetic signatures at the planetary surface. Continuous recordings of the transient
variations of the magnetic field onboard landers with three-axis magnetometer will then
provide constraints on the convection within the Martian magnetosphere.
Figure 6: The magnetometer boom is shown and the MAGNet sensor at the end of the
boom is displayed. The dimensions of the MAGNet sensor are 25x25x30mm.
Electric field sensor (ARES)
Located on the atmospheric sensor boom, this sensor will measure the vertical component
of the DC and AC up to 10 kHz electric fields and the conductivity of the atmosphere.
The objectives of ARES are to search for diurnal and seasonal variations of the quasi-DC
electric field, their relations with meteorological phenomena and to detect the
electromagnetic emissions in the environment. This takes also all its validity in the frame
of a network of stations. Of particular interest are the electrical charging phenomena and
possible break-down associated with dust devils or dust storms. The ATMIS/ARES mast
is shown on Figure 8.
Short-Period seismometer (SEIS SP) and Very BroadBand seismometer (SEIS VBB)
Seismic measurements will allow the characterization of the type of materials present in
the planet’s interior and the specification of Mars’ internal structure. Previous missions
did not detect any tectonic activity on Mars contrary to the Earth where tectonic motions
are the principal sources of seismic activity. Nevertheless, seismic events can occur on
Mars as a result of thermal variations, impacts of meteorites and atmospheric variations.
The objectives of SEIS are to determine the level and distribution of seismic activity, and
to determine the deep internal structure of the planet. The network achievements are
more important than any individual station (see Lognonné et al., 1996). Using ray
geometry, the observed arrival time of a body wave (either P or S) generated at the
surface, and recorded at the epicentral distance after traveling through a stack of
concentric spherical shells, is used to retrieve the wave velocities using a nonlinear
inverse method. In practice, the planetary models are subdivided in a number of shells of
variable size (Lognonné et al., 2003). Taking into account both the high-quality of the
seismometers which will be deployed on Mars in the future (Lognonné et al., 2000), and
the moderate level of seismicity which is expected for this planet (Phillips, 1991), it can
be reasonably expected that seismic velocity profiles of the Martian mantle will be
determined with an error lower or equal to 2%.
Figure 7: SEIS experiment instrument. It shows the seismometer electronics, very
broadband sensors (VBB), and structure.
Atmospheric package (ATMIS)
Made up of several sensors, the ATMIS experiment will register some meteorological
parameters at the surface (pressure, temperature, humidity, wind speed and direction,
optical depth, density of dust). Atmospheric data will also be recorded during the descent
and landing phase of the Netlander stations. The objectives of ATMIS are to characterize
the vertical structure of the Martian atmosphere from 140 km to the surface, and to
characterize near surface weather and boundary layer processes as a function of time each
day, during a complete seasonal cycle, and as function of the location on the Martian
surface.
As these phenomena are global, the more stations one has and the best
repartition one has, the better the results.
Wind sensor
1.8 m ATMIS/ARES BOOM
boom
Optical Depth sensor
Sensor
Temperature Sensor +Pressure/Humidity Sensor
Figure 8: Sensors for the ATMIS experiment.
Panoramic camera (PANCAM)
This camera will provide panoramic and stereoscopic (thus allowing for depth
perception) images, in five multispectral channels. It will be placed on top of a
deployable boom, one meter above the ground, and will be able to rotate 360°. The
objectives of PANCAM are to accurately locate landing sites and support network
science objectives to geologically investigate and map the landing sites, and to study
properties of the atmosphere and weather related phenomena (such as the optical depth).
Figure 9: PANCAM camera and deployable boom.
Ground Penetrating Radar (GPR)
This radar (Berthelier et al., 2000, 2003) will be used for the determination of the
directions of deep ground echoes. It will be able to detect any presence of underground
water. This instrument will also be used for the characterization of the soil density. It will
use a 35 meter long antenna. The objectives of GPR are to determine the characteristics
of subsurface layers, to determine the possible existence of ground ice layers and
subsurface features, to detect the possible existence of liquid ground water, to probe the
lower ionosphere, and to measure the electrical permittivity of the soil.
Motor for deploying 35 m ribbon
antenna
Camera Head showing location
of magnetic antenna
Figure 10: Parts of the GPR instrument.
Micro sensors for ground properties (SPICE)
This set of sensors will gather data related to soil properties, such as temperature. The
objectives are to measure the thermal and mechanical properties of the uppermost soil
layer.
Penetrating tips instrumented with force gauges
interface
sensor
washer
cup
sleeve
central rod
penetration
force
Figure 11: Penetrating tips instrumented with SPICE experiment. Not shown are 8
thermal probes distributed across bottom of lander and at end of MAGNet boom.
Radio system for geodesy experiments (NEIGE)
NEIGE will measure the frequency variations (Doppler shifts) of radio signals
transmitted between the NetLander and the orbiter, and between the orbiter and the Earth
(Barriot et al., 2001). These changes in frequency are due to the relative motion between
the source and the observer. The Doppler shift measurements will be used to derive the
variations of Mars’ rotation and to probe the ionosphere of Mars. The NEIGE objectives
are to determine from these data, several properties of the core, such as its density, size
and physical state. Also information will be obtained on the variations in mass and
pressure of the atmosphere, related to the seasonal sublimation/condensation process of
the polar ice caps. These objectives need at least two landers at the surface of Mars. An
additional NEIGE objective is to gain information on the Martian ionosphere, in
particular on effects of the solar wind, on the interactions with the local magnetic field
and on the escape of plasma (gas of charged particles). To achieve the NEIGE goals, the
positions of the four NetLanders, which will be fixed on the Martian surface, will be
determined from Doppler shifts of radio links between the NetLanders and the orbiter,
and between the orbiter and the Earth. Mars’s orientation and rotation velocity variations
will be deduced from those data. The ionosphere will disturb the propagation of these
signals and also the Doppler effect. It is, however, possible to determine this disturbance
by using two frequencies for the radio signals. Correct Netlander positions can then be
obtained, and the perturbation can be extracted to study the ionosphere.
A new synergetic procedure to derive the thermodynamical state and the mineralogical
structure of telluric planetary interiors has been developed by Verhoeven et al. (2004). As
inputs, one can consider the particular case of the electromagnetic, geodesic and
seismological data as provided by the network mission, supplemented with laboratory
measurements. This inverse problem is solved by means of a stochastic inversion.
Figure 12: Schematic view of the data transmission during the NEIGE experiment.
Microphone (MIC)
The microphone will record sounds from natural sources originating from atmospheric
phenomena like winds, storms, or electric activity. The objectives are to record sounds
associated with the movement of dust, electrical activity, and noises due to the wind and
its interaction with the lander structure, and to detect sounds generated by instrument
deployments and movements, and events during the entry, descent, and landing phase of
the mission.
Stereo Microphones
Camera
Head
Microphone
Electronics
Figure 13: MIC experiment situated on the camera head.
Conclusion
The Netlander experience demonstrated that a four-lander network that can be developed
at low cost (e.g. less than 100 Meuros) will address key science objectives on Mars. With
a total payload mass of about 6kg, the full network science as well as important multi-site
experiments associated to the search of water can be implemented.
Network science has complementary objectives with respect to the other Mars missions
and is still not implemented in the International Mars exploration scenario. Such a
mission is therefore mandatory for a full understanding of the formation of the planet and
of the geological evolution of Mars and all Netlander instruments will be excellent
candidates to a future Network mission.
Acknowledgement: The Scientific team want to acknowledge the Netlander technical
project team and the engineers and technicians participating to the instruments
developments. This paper is a contribution to the ’Les Houches’ workshop that was
supported by the European Community's Improving Human Potential Programme, under
contract RTN2-2001-00414, MAGE.
References
Anderson D.L., Miller W.F., Latham G.V., Nakamura Y., Toksoz M.N., Dainty A.M.,
Duennebier F.K., Lazarewicz A.R., Kowach R.L., and Knight T.C., 1977, Seismology
on Mars, J. Geophys. Res., 82, 4524-4546.
Banerdt B., Chicarro A.F., Coradini M., Federico F., Greeley R., Hechler M., Knudsen
J.M., Leovy C., Lognonné P., Lowry L., Mc Cleese D., McKay C., Pellinen R.,
Philipps R., Scoon G.E.N., Spohn T., Squyres S., Taylor F., and Wänke H., 1996,
InterMarsnet, Phase A study report, ESA Pub, SCI(96)2.
Barriot J.-P., Dehant V., Cerisier J.-C., Folkner W., Rhibes A., Benoist J., T. Van Hoolst,
R. Warnant, P. Defraigne, R.A. Preston, L. Romans, S. Wu, et A.W. Wernik, 2001,
NEIGE: NetLander Ionosphere and Geodesy Experiment. In: Proc. COSPAR meeting,
Warsaw, Poland, Advances in Space Research, 28(8), 1237-1249.
Berthelier J.J., Ney R., Costard F., Hamelin M., Meye A., Martinat B., Reineix A.,
Hansen Th., Bano M., Kofman W., Lefeuvre F., and Paillou Ph., 2000, The GPR
experiment on NETLANDER, Planet. Space Sci., 48(12), 1161-1180.
Berthelier J.J., Ney R., Ciarletti V., Reineix A., Martinat B., Hamelin M., Costard F.,
Paillou Ph., Duvanaud C., Nevejans D., Kofman W., Trotignon J.G., Grandjean G.,
Zamora M., Nagy A., 2003, GPR, a ground penetrating radar for the NETLANDER
mission, J. Geophys. Res. - Planets, 108, DOI:1029/2002JE001866.
Chicarro A.F., Coradini M., Fulchignoni M., Hiller K., Knudsen J.M., Liede I., Lindberg
C., Lognonné P., Pellinen R., Spohn T., Taylor F., Scoon G.E.N., and Wänke H.,
1993, Marsnet, Phase A Study Report, ESA Pub., SCI(93)2.
Dehant V., Van Hoolst T., and Defraigne P. , 2000, Comparison between the nutations of
the planet Mars and the nutations of the Earth, Survey Geophys., 21, 89-110.
Folkner W.M., R.D. Kahn, R.A. Preston, C.F. Yoder, E.M. Standish, J.G. Williams, C.D.
Edwards, and R.W. Hellings, 1997, Mars dynamics from Earth-based tracking of the
Mars Pathfinder Lander, J. Geophys. Res., 102, 4057-4064.
Harri A.-M., Marsal O., Leppelmeier G.W., Lognonné P., Glassmaier G., Angrilli F.,
Banerdt W.B., Barriot J.-P., Bertaux J.-L., Berthelier J.-J., Calcutt S., Cerisier J.-C.,
Crisp D., Dehant V., Di Pippo S., Giardini D., Guerrier D., Jaumann R., Kumpulainen
K., Langevin Y., Larsen S., Menvielle M., Musmann G., Polkko J., Pommereau J.P.,
Runavot J., Schumacher W., Siili T., Simola J., and Tillman J.E., 1999, Network
Science Landers for Mars. In: Proc. COSPAR Meeting, Session BO.4 on `Return to
Mars', Advances in Space Research, 23(11), 1915-1924.
Lognonné P. and Mosser B., 1993, Planetary Seismology, Survey in Geophysic, 14, 239302.
Lognonné Ph., Gagnepain Beyneix J., Banerdt W.B., Cacho S., Karczewski J.F., and
Morand M., 1996, Ultra broad band seismology on InterMarsNet. Planet. Space Sci.
44, 1237-1249.
Lognonné P., Zharkov V.N., Karczewski J.F., Romanowicz B., Menvielle M., Poupinet
G., Brient B., Cavoit C., Desautez A., Dole B., Franqueville D., Gagnepain-Beyneix
J., Richard H., Schibler P., Striebig N., 1998, The Seismic Optimism Experiment,
Planetary Space Sciences, 46, 739-747.
Lognonné P, Harri A.M., Marsal O., Angrilli F., Banerdt B., Barriot J.P., Bertaux J.L.,
Berthelier J.J., Calcutt S., Cerisier J.C., Crisp D., Dehant V., Giardini D., Jaumann R.,
Langevin Y., Menvielle M., Mussman G., Pommereau J.P., Spohn T., and the
Netlander team, 1999, Netlander: the first geoscience network on Mars, Mars
International Conférence, Paris, February 1999.
Lognonné P., Giardini D., Banerdt B., Gagnepain-Beyneix J., Mocquet A., Spohn T.,
Karczewski J.F., Schibler P., Cacho S., Pike T., Cavoit C., Desautez A., Pinassaud J.,
Breuer D., Campillo M., Defraigne P., Dehant V., Deschamp A., Hinderer J., Lévêque
J.J., Montagner J.P., and Oberst J., 2000, The NetLander Very Broad Band
Seismometer, Planet. Space Sci., 48, 1289-1302.
Lognonné P., Gagnepain-Beyneix J., and Chenet H., 2003, A new seismic model of the
Moon: implication in terms of structure, formation and evolution, Earth Plan. Sci.
Let., 6637, 1-18.
Lognonné P, Spohn T., and Giardini D., 2003, Mars in depth, Astronomy and
Astrophysics, 44 (4), page 15.
Menvielle M., Musmann G., Kuhnke F., Alexandrescu M., Berthelier J.-J., Glassmeier
K.-H., Motschmann U., Pajunpaa K., Pinçon J.-L., Primdahl F., and Szarka L., 2000,
Contribution of magnetic measurements onboard NetLander to Mars exploration.
Planet. Space Sci., 48, 1231-1248.
Nakamura Y., 1983. Seismic velocity structure of the lunar mantle, J. Geophys. Res., 88,
677-686.
Phillips, R. J. , 1991, Expected rate of Marsquake. Scientific Rationale and Requirements
for a global seismic Network on Mars, LPI Technical Report 91-02, Lunar and
Planetary Institute, Houston, Tx., pp. 35-38.
Pinçon J.-L., Menvielle M., and Szarka L., 2000, Electromagnetic sounding of Mars with
magnetic network data by using a high resolution multi-point data analysis technique.
Planet. Space Sci., 48, 1261-1270.
Sotin C., Rocard F., and Lognonné P., 2000, Summary of the Internationnal Conference
of Mars Exploration Program and Sample Return mission, Planet. Space Sc., 48,11431144.
Van Hoolst T., Dehant V., Roosbeek F., and Lognonné P., 2003, Tidally induced surface
displacements, external potential variations, and gravity variations on Mars, Icarus,
161, 281-296.
Verhoeven O., Rivoldini A., Vacher P., Mocquet A., Choblet G., Menvielle M., Dehant
V., and the MINT team, 2004, Planetary interiors structure inferred from
electromagnetic, geodesic and seismic network science I: Forward problem and the
case of Mars, J. Geophys. Res., in preparation.
Yoder C.F., Konopliv A.S., Yuan D.N., Standish E.M., and Folkner W.M., 2003, Fluid
core size of Mars from detection of the solar tide, Science, 300, 299-303.