The InSight mission was selected by NASA in August 2012 as part of the DISCOVERY program. On November 26, 2018, it deployed the first geophysical observatory on Mars, in order to provide essential scientific knowledge to understand the fundamental processes of the formation of telluric planets and their evolution. To achieve this, InSight uses two scientific instruments: the SEIS seismometer and HP3, an instrument for measuring the heat flux from the heart of the planet.
The SEIS seismometer, measuring seismic activity, meteorite impact flux and measurements of the Phobos tide, characterizes the interior structure of Mars, providing information on crustal thickness and structure, composition and mantle structure and core size. It has involved more that 10 years of development by the Institut de Physique du Globe de Paris (IPGP) with the support of CNES and CNRS, and a wide range of international partners: IPGP, Swiss Federal Institute of Technology in Zurich (ETHZ), Max-Planck Institute in Lindau, Imperial College London and Oxford, Jet Propulsion Laboratory) and ISAE-SUPAERO.
SEIS is the lowest noise seismometer in the entire Solar System!
Among the researchers of the SSPA team we have two co-investigators of the mission (David Mimoun, Raphael Garcia) as well as 5 collaborators. The SSPA team has contributed to the InSight mission notably through the performance model of the SEIS instrument, the performance model of the mission, the specification of the scientific software and the design of the concept of operations of the instrument on Mars. We also contribute significantly to the exploitation of scientific data on the structure of the crust, the internal structure of the planet or the study of convective vortices ("dust devils").
Here are some SSPA research topics related to the InSight mission:
Development of a noise model for the SEIS instrument
Variations in wind (Murdoch et al. 2017), atmospheric pressure (Murdoch et al., 2018, Garcia et al., 2020), magnetic field or even temperature are natural phenomena that create noise on the SEIS instrument. Understanding and predicting such sources of noise (Mimoun et al., 2017) was important in the design of the mission, the definition of specifications and in the exploitation of the data. To help NASA and the InSight team choose the best possible location for the SEIS instrument, we also made performance and noise maps of each point around the lander. They identify all the noises likely to disturb the measurements of the instrument and take into account all the known characteristics of the Martian environment.
Using seismology to constrain internal structure
Constraining the interior structure of telluric planets (the Earth, Mars, the Moon) constitutes a fundamental issue to better understand their processes of formation and their evolution. To achieve this goal, the records from seismologic stations are keys to probe planets’ interior. In this framework, an important axe of research is to develop inversion algorithms of seismologic data, and more broadly geophysical data, in order to estimate velocity and temperature profiles within the planets, and their mineralogical composition (Drilleau et al., 2013, 2020 ; Panning et al., 2015, 2017 ; Bissig, 2018 ; Garcia et al., 2019).
Estimating the properties of Martian regolith
Determining the structure of near surface provides constraints on the geologic history of a planet. The pressure fluctuations of the Mars’ atmosphere induce tiny deformations of the ground, that can be measured by the SEIS seismometer of the InSight mission. These deformations depend on the elastic properties of the regolith. From the records of pressure, wind, and ground deformation data, the elastic parameters below the lander can be estimated in the first 20 m below the surface (Lognonné et al., 2019, Kenda et al., 2020, Garcia et al., 2020, Murdoch et al., 2020). The first results show the presence of a transition between the regolith at the surface and a stiffer rock, which could be a blocky layer ejected during a meteoritic impact (Lognonné et al., 2020).
Studying convective vortices (dust devils)
InSight measures wind speed, direction and air pressure nearly continuously, offering more data than pervious landed missions. These meteorological sensors have detected hundreds of passing convective vortices (whirlwinds), which are called dust devils when they pick up dust and become visible. The InSight site actually has more whirlwinds than any other place we’ve landed on Mars while carrying weather sensors (Banfield, Spiga et al., 2020). SEIS can feel these vortices pulling on the surface like a giant vacuum cleaner (Lorenz et al., 2015). In addition to being able to calculate just how elastic the Martian surface is by measuring the tug of passing dust devils (Lognonné et al., 2020; Banerdt et al., 2020), combined seismic and pressure measurements allow constraints to be made on vortex properties and trajectories (Murdoch et al., 2020) and can indicate heterogeneities in the sub-surface structure around the InSight lander (Golombek et al., 2020).