By jointly studying seismic data and orbital observations linked to two major meteorite impacts from late 2021, the international teams of NASA’s InSight and Mars Reconnaissance Orbiter missions are refining their knowledge of the Martian planetary interior. Two studies published on October 27 in the journal Science, involving many co-authors from French institutions and laboratories, including CNRS, the Institut de Physique du Globe de Paris, Université Paris Cité, and supported by CNES and ANR, provide new constraints to validate and refine models of the internal structure of the planet previously proposed, but also the dynamics of major impacts and the physics of atmospheric shock waves.
While meteorite impacts shape planetary surfaces in the solar system, it is rare to be able to record signals related to high-powered impacts. On Earth, our atmosphere protects us! Most meteorites burn up, end up as shooting stars or explode at high altitude. Very few reach the ground. And few other bodies in the solar system are equipped with seismometers. If natural impacts had already been recorded on the Moon, it was impossible to link the strongest of them to a crater image, which would have allowed to know their precise characteristics.
On Mars, the impacts previously recorded by the SEIS instrument were located within 300 km of the InSight lander and were associated with craters about 10 meters in diameter. These data, via the analysis of acoustic waves, have already improved our knowledge of the local structure of the crust.
Impacts S1000a and S1094b, which occurred on September 18 and December 24, 2021, respectively, left two footprints of more than 130 meters in diameter on the surface of Mars. For S1094b, it is even the largest impact crater of the last centuries detected on a terrestrial planet, since its diameter of 150 meters exceeds the 120 meters of the Wabar crater, in Saudi Arabia, considered as the largest of the impacts having reached the surface of the Earth during this period, several decades before the deployment of the first seismographs at the beginning of the 20th century. The same is true on Mars, where no impact of this size had ever been detected by the Mars Reconnaissance Orbiter (MRO) mission since the beginning of its orbital mission 16 years ago.
By combining seismic data from InSight’s SEIS and MRO’s CTX, MARCI and HiRISE cameras, the international teams of the two NASA missions were able to pinpoint the location of these two events in time and space: “The dynamics of the impact and the development of the shock wave have been documented by our seismometer and by the very high-resolution images from Mars Reconnaissance Orbiter. This allows us to better understand how the energy of such a bolide is distributed in the subsurface and in the atmosphere. In addition, we now have two seismic sources with an equivalent magnitude greater than 4 and whose position is perfectly known on Mars, and which allow us to validate our models of the internal structure of the upper mantle and the crust, developed in particular within the framework of the MAGIS project,” says Philippe Lognonné, scientific leader of the SEIS experiment at the Institut de Physique du Globe de Paris, second author of one of the two articles, coordinator of the MAGIS project funded by the French National Research Agency (ANR) and professor at Université Paris Cité.
The two meteorites hit Mars at 3500 km and 7500 km from the Insight landing site. The largest one has an estimated mass between 250 and 650 tons, for an impact speed of 7.5 km/s. Both have released enough energy to generate both surface waves and volume waves propagating to the core of Mars.
For Eric Beucler, professor at Nantes University and co-author of the papers “These are the first events for which surface waves are clearly visible. This allows us to determine the average structure of the Mars crust between the impact point and InSight”. These measurements of crustal thickness are fundamental to understanding the evolution of Mars and have so far only been possible under the InSight station thanks to the volume waves of earthquakes. Other observations of surface waves have since been made, in particular after an earthquake of magnitude 4.7 detected on May 4, 2022, which will allow to complete these analyses.
A few weeks before the 4th anniversary of its landing on Mars, the InSight mission and its main instrument, the SEIS seismometer, have made it possible to build the first models of the internal structure of Mars and to observe both the seismicity of the planet and the very strong impacts that a planet with a tenuous atmosphere can encounter.
Thierry Damerval, President and CEO of the French National Research Agency (ANR), said that “with the MAGIS project and these unique data recorded by InSight and MRO, the work of the Franco-American teams of IPGP and Los Alamos National Laboratory (LANL) will allow us to better understand the very strong planetary impacts of meteorites.
Antoine Petit, president and CEO of CNRS, said: “Mars continues to surprise us. The analysis of the InSight and Mars Orbiter data by international teams, including a large number of scientists from our laboratories, allows us to refine our knowledge of the interior of the planet Mars and thus demonstrates the importance of these space missions for a better understanding of the solar system. This work prefigures the future lunar mission FSS (Farside Seismic Suite) which aims to deposit an autonomous seismometer on the far side of the Moon.
And for Philippe Baptiste, president of CNES, “These are fantastic results that show the relevance and the very high level of performance of the SEIS instrument. Mars continues to give us its secrets. With one of the spare SEIS sensors, the FSS mission will take over in 2025 on the Moon. JPL, CNES, IPGP and their partners will then be able to investigate the interior of the Moon for the first time since the Apollo missions”.
About InSight and SEIS
JPL manages the InSight mission on behalf of NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery program, managed by the Marshall Space Flight Center (MSFC), a NASA facility in Huntsville, Alabama. Lockheed Martin Space in Denver built the InSight probe, including its cruise stage and lander, and supports spacecraft operations for the mission. CNES is the prime contractor for SEIS, and the Paris Institute of Globe Physics (Université Paris Cité/IPGP/CNRS) has scientific responsibility. CNES finances the French contributions, coordinates the international consortium (*) and has been responsible for the integration, testing and delivery of the complete instrument to NASA. IPGP designed the VBB (Very Broad Band) sensors, tested them before their delivery to CNES and contributes to the operation of the VBBs on Mars.
SEIS and APSS operations are conducted by CNES within the FOCSE-SISMOC, with the support of the Centro de Astrobiologia (Spain). SEIS data are formatted and distributed by the Mars SEIS Data Service of the IPG Paris, within the framework of the InSight National Observation Service to which the LPG also contributes and, for the Sismo activities at the School, GeoAzur. The daily identification of earthquakes is ensured by the Mars Quake Service of InSight, a collaborative operational service led by ETH Zurich to which seismologists from IPG Paris, the University of Bristol (UK) and Imperial College London (UK) also contribute.
Several other CNRS laboratories including LMD (CNRS/ENS Paris/Ecole polytechnique/Sorbonne University), LPG (CNRS/Nantes University/Le Mans University/University of Angers), IRAP (CNRS/University of Toulouse/CNES), LGL-TPE (CNRS/Ecole normale supérieure de Lyon/Université Claude Bernard Lyon 1), IMPMC (Sorbonne University/National Museum of Natural History/CNRS) and LAGRANGE (CNRS/University of Côte d’Azur/Observatoire de la Côte d’Azur) are participating with IPGP and ISAE-SUPAERO in the analyses of the InSight mission data. These analyses are supported by the CNES and the French National Research Agency as part of the ANR MArs Geophysical InSight (MAGIS) project.
(*) in collaboration with SODERN for the realization of the VBB, JPL, the Swiss Federal Institute of Technology (ETH, Zürich, Switzerland), the Max Planck Institute for Solar System Research (MPS, Göttingen, Germany), Imperial College London and Oxford University provided the SEIS subsystems and participate in the scientific exploitation of SEIS.
- Scientific papers
- Largest recent impact craters on Mars: Orbital imaging and surface seismic co-investigation by L. V. Posiolova, P. Lognonné, W. B. Banerdt, J. Clinton, G. S. Collins,T. Kawamura, S. Ceylan, I. Daubar, B. Fernando, M. Froment, D. Giardini, M. C. Malin, K. Miljković, S. C. Stähler, Z. Xu, M. E. Banks,E. Beucler, B. A. Cantor, C. Charalambous, N. Dahmen, P. Davis, M. Drilleau, C. M. Dundas, C. Duran,F. Euchner, R. F. Garcia, M. Golombek, A. Horleston, C. Keegan, A. Khan, D. Kim,C. Larmat, R. Lorenz, L. Margerin, S. Menina, M. Panning, C. Pardo, C. Perrin, W. T. Pike, M. Plasman, A. Rajšić, L. Rolland, E. Rougier, G. Speth, A. Spiga, A. Stott, D. Susko, N. A. Teanby, A. Valeh, A. Werynski, N. Wojcicka, G. Zenhäusern. Science, 2022 – DOI : 10.1126/science.abq7704
- Surface Waves and Crustal Structure on Mars by D. Kim, W. B. Banerdt, S. Ceylan, D. Giardini, V. Lekic, P. Lognonné, C. Beghein, É. Beucler, S. Carrasco, C. Charalambous, J. Clinton, M. Drilleau, C. Durán, M. Golombek, R. Joshi, A. Khan, B. Knapmeyer-Endrun, J. Li, R. Maguire, W. T. Pike, H. Samuel, M. Schimmel, N. Schmerr, S. C. Stähler, E. Stutzmann, M. Wieczorek, Z. Xu, A. Batov, E. Bozdag, N. Dahmen, P. Davis, T. Gudkova, A. Horleston, Q. Huang, T. Kawamura, S. King, S. M. McLennan, F. Nimmo, M. Plasman, A. C. Plesa, I. E. Stepanova, E. Weidner, G. Zenhäusern, I. J. Daubar, B. Fernando, R. Garcia, L. V. Posiolova, M. P. Panning. Science, 2022 – DOI : 10.1126/science.abq7157
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