Recent discoveries regarding the Martian mantle have unveiled significant findings about the planet's interior structure and its ancient history. Evidence suggests that large lumps of rocky material, remnants from massive impacts that occurred over 4.5 billion years ago, are scattered throughout Mars' mantle. This groundbreaking research was made possible by NASA's now-retired InSight lander, which collected vital data before the conclusion of its mission in 2022.
The research indicates that these ancient impacts released immense energy, sufficient to melt vast portions of the early Martian crust and mantle, creating massive magma oceans. This process also injected fragments of both the impacting bodies and Martian debris deep into the planet's interior. However, the exact nature of these ancient impactors remains a mystery, as the early solar system was populated by various rocky objects, including protoplanets.
The remnants of these catastrophic events manifest as lumps within the Martian mantle, some measuring up to 2.5 miles (4 kilometers) across. Unlike Earth, which has tectonic plates that recycle its interior through convection, Mars’ lack of tectonic activity has preserved these features, offering a unique glimpse into the planet's geological past.
The findings were reported on August 28 in a study published in the journal Science. According to the lead author, Constantinos Charalambous from Imperial College London, "We’ve never seen the inside of a planet in such fine detail and clarity before." The study reveals that the Martian mantle is filled with ancient fragments, suggesting that it has evolved slowly over billions of years. In contrast, similar features on Earth may have been largely erased due to its dynamic tectonic activity.
NASA’s InSight mission, managed by the Jet Propulsion Laboratory in Southern California, successfully placed the first seismometer on Mars' surface in 2018. This sensitive instrument recorded a total of 1,319 marsquakes during its operational lifespan, allowing scientists to study the seismic waves produced by these quakes and gain insights into Mars' crust, mantle, and core.
Unlike Earth, which is characterized by tectonic plate activity, Mars experiences two other types of quakes: those caused by rocks cracking under heat and pressure, and those triggered by meteoroid impacts. The latter generates high-frequency seismic waves that penetrate from the crust into the mantle. A paper published earlier this year in Geophysical Research Letters highlighted how these meteoroid impacts produce seismic waves, providing further insights into the Martian interior.
The latest study identified eight marsquakes with high-frequency energy that reached deep into the mantle, where the seismic waves underwent distinct alterations. Initially, researchers assumed these changes were occurring within the Martian crust. However, they later discovered that the alterations happened primarily within localized regions of the mantle, revealing lumps of material with compositions different from the surrounding area.
The team hypothesized that these lumps resulted from giant asteroids or other rocky materials striking Mars during the early solar system, generating the magma oceans and carrying fragments into the mantle. Charalambous likened the distribution of these lumps to "shattered glass," consisting of large shards interspersed with smaller fragments. This pattern is consistent with the energy released during significant impacts, which scattered debris throughout the mantle.
The persistence of these fine structures suggests that Mars has not experienced the vigorous geological processes that would have smoothed out these features. This discovery may provide valuable insights into other rocky planets lacking tectonic plates, such as Venus and Mercury. Charalambous emphasized that Mars could hold clues about the geological processes occurring beneath the surfaces of these neighboring planets.
NASA's InSight mission was managed by the Jet Propulsion Laboratory for the Science Mission Directorate. It was part of NASA’s Discovery Program, with contributions from several international partners, including France's Centre National d’Études Spatiales (CNES) and the German Aerospace Center (DLR). The mission's success was made possible through collaborative efforts, including the development of the Seismic Experiment for Interior Structure (SEIS) instrument and the Heat Flow and Physical Properties Package (HP3).
For further inquiries regarding the InSight mission, please contact:
Andrew Good, Jet Propulsion Laboratory, Pasadena, Calif.
Phone: 818-393-2433
Email: andrew.c.good@jpl.nasa.gov
Karen Fox / Molly Wasser, NASA Headquarters, Washington
Phone: 202-358-1600
Email: karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
