As the Red Planet turns, its spin is quickening, according to new findings that reveal the discovery of “hidden structures” pointing to the existence of a gravity anomaly 1,200 kilometers below the Martian surface.
The findings, detailed in a new paper in the journal JGR Planets, report the discovery of what researchers characterize as a “large mass anomaly” beneath Tharsis Rise, a massive volcanic plateau located near the Martian equator.
“The NASA InSight mission has given us new information about the crust of Mars, which means that we can reexamine how we understand the support for the Tharsis Rise,” the paper’s authors said in a summary of its findings.
A “Large Mass Anomaly” is Revealed
Existing data on the surface gravitational signals of Mars appear to conform to recent models, according to the Dutch researchers behind the study, which includes team members Bart Root, Weilun Qin, and Youandi van der Tang of the Delft University of Technology, as well as Cedric Thieulot with the University of Utrecht, Netherlands.
“The gravity signal of its surface fits well with our model that represents the planet as a thin elastic shell,” the team reports. “This model suggests that Mars can be modeled with a crust of about 55 km thick and an elastic rigidity layer of approximately 100 km thick.”
Yet, despite models of the Red Planet’s thin outer shell being mostly aligned with observational data, the team notes that there were still deviations in some locations—particularly concerning the unusual gravity field displayed around the Tharsis Region.
Based on their research, a “large mass anomaly” located beneath the Tharsis volcanic plateau would potentially explain the unusual gravity signals from the location, adding that their analysis revealed the presence of “hidden structures in the Martian crust that do not have surface expressions,” which the team believes point “a much more complex geology of Mars hidden by the surface.”
A Volcanic Curiosity on the Red Planet
Past studies of the Tharsis Region had already revealed the presence of a long-wavelength gravity anomaly in the area, although past modeling had failed to offer any definitive answer about its possible relationship to the volcanic complex’s topography and structural attributes, particularly within the Martian crust.
NASA’s InSight mission has helped to unravel some of the questions about the Red Planet’s composition, including the rigid outer portion of Mars known as its lithosphere. Based on the InSight mission data, the Dutch team behind the new research decided this warranted “a reanalysis of the support of the Tharsis Region.”
They began with an examination of the existing topographic and gravity signal data, which revealed that models involving a “thin shell” of Mars provided a good match for the existing gravity field, particularly in terms of crustal thickness at Elysium, the second largest volcanic region on Mars after its Tharsis Region.
The team’s “thin shell flexure” model assumed average crustal thicknesses of around 55 kilometers, with crustal densities at 3,050 kilograms and mantle densities of 3,750 kilograms per cubic meter. Finally, an elastic thickness of 100 kilometers was calculated.
Based on deviations between the team’s models and observed gravitational fields in the region, they concluded that this points to dynamic support for the volcanic region that, as revealed through additional modeling, led the team to believe that “a substantial negative mass anomaly” exists within the mantle beneath Tharsis Rise.
The Quickening of Mars’ Spin
This anomaly likely consists of extremely high-temperature mantle material, which the team believes can explain the well-known long-wavelength gravity phenomenon associated with Tharsis. Additionally, the researchers say that the short-scale gravity residuals they observed can provide insights into the geological structure of Mars, as well as its crustal density.
However, the team notes that despite their findings at Tharsis, the same phenomena may not yet explain all the unusual below-ground features that are known to exist in various regions on Mars.
“Buried mass anomalies in the subsurface of the northern polar plains seem not to be related to any geological or surface expressions,” the team clarifies, which they believe could point to “a more complex geology of the northern Martian crust than is suggested by the surface topography.”
Nonetheless, the team notes that apparent increases in the rotation of Mars, first revealed in data collected by NASA’s Viking lander in the mid 1970s, are likely linked to the “upward rising negative mass anomaly in the mantle” revealed by their new research.
The increasing rate of the planet’s spin, they conclude, “could be explained by our estimated mass anomaly,” although they add that “more precise analysis is needed to take into account the huge uncertainty in flow velocity in the mantle of Mars.”
The team’s new paper, “Describing the Global Gravity Field of Mars With Lithospheric Flexure and Deep Mantle Flow,” appeared in JGR Planets on February 18, 2026.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.