Scientists have analyzed anomalies in the gravitational field of Mars. They have revealed much about the irregularity of its internal structure. In particular, they found numerous dense structures near the Solar System’s largest volcano, Olympus Mons.
Geological structure of Mars
Studies of Mars’ gravity field variations have found dense, large-scale structures hidden beneath the sedimentary layers of the lost ocean. The analysis, which combines models and data from several missions, also shows that active processes in the Martian mantle may be contributing to the eruption of the Solar System’s largest volcano, Olympus Mons. The findings were presented this week at the Europlanetary Science Congress (EPSC) in Berlin by Bart Root of Delft University of Technology (TU Delft).
Mars has many hidden structures such as ice deposits, but features found on the northern polar plains remain a mystery because they are covered by a thick and smooth layer of sediment that is believed to have been deposited on the ancient seafloor.
“These dense structures may be of volcanic origin or compacted material due to long ago impacts. These dense structures could be volcanic in origin or could be compacted material due to ancient impacts. There are around 20 features of varying sizes that we have identified dotted around the area surrounding the north polar cap—one of which resembles the shape of a dog,” said Dr. Root. “There seems to be no trace of them at the surface. However, through gravity data, we have a tantalizing glimpse into the older history of the northern hemisphere of Mars.”
Density map of Mars
Dr. Root and his colleagues from Delft and Utrecht Universities used tiny deviations in the moons’ orbits to study Mars’ gravitational field and find clues about the planet’s internal mass distribution. These data were fed input into models using new observations from NASA’s Insight mission about the thickness and flexibility of the Martian crust, as well as the dynamics of the planet’s mantle and deep interior, to create a global density map of Mars.
The density map indicates that the north polar objects are approximately 300-400 kg/m3 denser than their surroundings. However, the study has also opened up new insights into the structures underlying the vast volcanic region of the Tharsis Rise, which includes the colossal Olympus Mons volcano.
Volcanic processes on Mars
Although the volcanoes are very dense, the Tharsis region is much higher than the average surface of Mars and is surrounded by a region of relatively weak gravity. This gravitational anomaly is difficult to explain by focusing only on the differences in the Martian crust and upper mantle. The study by Dr. Root and his team suggests that a low-density region measuring about 1,750 kilometers across and 1,100 kilometers deep is pushing up the entire Tharsis region. This can be explained by a huge plume of lava deep in the Martian interior moving toward the surface.
“The NASA InSight mission has given us vital new information about the hard outer layer of Mars. This means we need to rethink how we understand the support for the Olympus Mons volcano and its surroundings,” said Dr. Root. “It shows that Mars might still have active movements happening inside it, affecting and possibly making new volcanic features on the surface.”
Exploring the Martian interior
Dr. Root is part of the team proposing the Martian Quantum Gravity (MaQuls) mission, which aims to use technology developed for missions such as GRAIL and GRACE on the Moon and Earth, respectively, to map the gravity field of Mars in detail.
“Observations with MaQuIs would enable us to better explore the subsurface of Mars. This would help us to find out more about these mysterious hidden features and study ongoing mantle convection, as well as understand dynamic surface processes like atmospheric seasonal changes and the detection of ground water reservoirs,” said Dr. Lisa Wörner of DLR, who introduced the MaQuI mission at this week’s EPSC2024 conference.
According to phys.org
