Ancient preserved heterogeneities discovered in Mars’ mantle thanks to data from the InSight mission
An international team led by Imperial College London, the Institut de Physique du Globe de Paris / Université Paris Cité, Johns Hopkins University, the University of Oxford and NASA’s Jet Propulsion Laboratory reports in Science (August 28, 2025) that Mars’ present-day mantle contains a multitude of kilometer-scale heterogeneous fragments. These heterogeneities are thought to be the result of differentiation processes that took place over 4 billion years ago, and were revealed thanks to data from NASA’s InSight lander and its SEIS seismometer, designed in France under the scientific responsibility of the Institut de Physique du Globe de Paris (IPGP, Université Paris Cité/CNRS) with support from CNES and European partners.
Representation of Mars’ evolution from a giant impact more than 4 billion years ago to the planet we know today. @vadimsadovski / Imperial College London
Ancient heterogeneous fragments distributed beneath the surface
By studying eight high-frequency marsquakes, researchers identified anomalies in the propagation of unusually slow seismic waves, revealing the presence of 1–4 km-wide heterogeneities within the mantle that “slow down” seismic waves when they encounter these kilometer-scale fragments. Tracing back in time, the researchers concluded that these heterogeneities, whose size has progressively decreased over time, originated from very ancient processes, possibly linked to asteroids colliding with Mars in the early Solar System.
When striking the planet’s surface, these asteroids may have generated magma oceans whose solidification created compositional heterogeneities. Such impacts could also have carried ancient fragments of crust and lithosphere deep into the mantle. On Earth, plate tectonics continuously recycles oceanic crust and lithosphere, gradually mixing them with other ancient heterogeneities through convection. On Mars, however, where plate tectonics is absent and mantle convection is weaker, this permanent recycling does not occur, and mixing is less efficient. The survival of these fine-scale structures, still detectable today, demonstrates that Mars has not undergone the same evolution as our planet.
“We had never observed the interior of a planet with such detail,” explains Constantinos Charalambous (Imperial College). “Mars’ mantle is scattered with ancient fragments, whose preservation reflects the planet’s slow and subdued evolution.”
“The survival of these fragments after several billion years of convective stirring also provides valuable insights into the rheology of the Martian mantle,” adds Henri Samuel, CNRS researcher (IPGP/UPC) and co-author of the study. “Mars’ mantle appears to be more rigid than Earth’s, limiting deformation and mixing of ancient heterogeneities.”
“These results confirm that Mars preserves a unique geological memory, while Earth, with its active tectonics, has erased similar traces of its past,” notes Thomas Pike (Imperial College), co-author of the study.
The contribution of French and European teams
Deployed on Mars’ surface in 2018, SEIS (Seismic Experiment for Interior Structure) recorded 1,319 marsquakes before the mission ended in December 2022. This ultra-sensitive instrument was provided by CNES to NASA, with scientific responsibility entrusted to Philippe Lognonné (IPGP).
These new observations highlight the scientific wealth still contained in the InSight data:
“Discovery after discovery, Mars stands out with an internal structure very different from Earth’s. And by comparing terrestrial planets, we can only recognize Earth’s uniqueness,” emphasizes Philippe Lognonné, Professor at Université Paris Cité and co-author of the study.
Sources
Seismic evidence for a highly heterogeneous Martian mantle
C. Charalambous, W. T. Pike, D. Kim, H. Samuel, B. Fernando, C. Bill, P. Lognonné, W. B. Banerdt, Science, 2025
https://www.science.org/doi/10.1126/science.adk4292
@vadimsadovski / Imperial College London
Representation of the evolution of Mars, moving counterclockwise, from a giant impact that occurred more than 4 billion years ago to the planet we know today. Early impacts in Mars’ history created one or several magma oceans and may have buried ancient fragments deep within the young planet. The rapid solidification of these magma oceans also generated ancient heterogeneities. As Mars cooled, it formed a solid crust and a stagnant lid that trapped heat and slowed the planet’s internal motions.
Over the following billions of years, Mars’ interior evolved under the influence of slow convection currents that deformed and partially mixed these ancient structures, leaving behind a heterogeneous interior made up of remnants scattered throughout the silicate mantle. These surviving debris—some large, others much smaller and more dispersed—form a geological time capsule, preserving clues about the planet’s earliest moments. Today, seismic waves from a much more recent meteorite impact, far smaller than the primordial ones, travel through this complex interior. By studying the dispersion and evolution of these waves, NASA’s InSight lander has revealed hidden details about the deep past and history of the Red Planet.
About InSight and SEIS:
NASA’s InSight mission officially ended in December 2022 after more than four years of collecting unique scientific data on Mars.
JPL managed the InSight mission for 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 spacecraft, including its cruise stage and lander, and supported spacecraft operations throughout the mission. CNES was the prime contractor for SEIS, with the Institut de Physique du Globe de Paris (Université Paris Cité/IPGP/CNRS) serving as its scientific lead. CNES funded the French contributions, coordinated the international consortium (*), and was responsible for the integration, testing, and delivery of the complete instrument to NASA. IPGP designed the Very Broad Band (VBB) sensors, tested them before delivery to CNES, and contributes to the operation of the VBBs on Mars.
SEIS and APSS operations were conducted by CNES within FOCSE-SISMOC, with support from the Centro de Astrobiología (Spain). SEIS data are formatted and distributed by the Mars SEIS Data Service at IPGP, as part of the InSight National Observation Service, which also involves LPG and, for the Sismo at School activities, GéoAzur. The daily identification of marsquakes was carried out by the InSight Mars Quake Service, a collaborative operational service led by ETH Zurich, with contributions from seismologists at IPGP, the University of Bristol (UK), and Imperial College London (UK).
Several other CNRS laboratories, including LMD (CNRS/ENS Paris/École Polytechnique/Sorbonne Université), LPG (CNRS/Nantes Université/Le Mans Université/Université d’Angers), IRAP (CNRS/Université de Toulouse/CNES), LGL-TPE (CNRS/École Normale Supérieure de Lyon/Université Claude Bernard Lyon 1), IMPMC (Sorbonne Université/Muséum National d’Histoire Naturelle/CNRS), and LAGRANGE (CNRS/Université Côte d’Azur/Observatoire de la Côte d’Azur), together with IPGP and ISAE-SUPAERO, contribute to the analysis of InSight mission data. These analyses have been supported by CNES and the French National Research Agency (ANR) through the MArs Geophysical InSight (MAGIS) project.
(*) In collaboration with SODERN for the development of the VBB, JPL, ETH Zurich (Switzerland), the Max Planck Institute for Solar System Research (MPS, Göttingen, Germany), Imperial College London, and the University of Oxford provided SEIS subsystems and are involved in SEIS scientific operations.
