New research into the interior of Mars further emphasizes that the Red Planet is a world of two very different halves. Deep in Mars’ southern hemisphere, the temperature is up to 750 degrees Fahrenheit (400 degrees Celsius) warmer than beneath the northern hemisphere, deepening the mystery of the strange dichotomy between the Red Planet’s flattened north and the rugged southern highlands. “Scientists generally assume that the interiors of planetary bodies are generally spherically symmetric, but this is not necessarily true,” Alexander Berne, formerly of Caltech and now at the University of Arizona, said in a statement. Berne is the lead author of a new research paper revealing the discovery of the strange southern hot spot. Berne and his team went back and examined archival data from three NASA spacecraft (Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter) to look for subtle changes in their orbital speed that could reflect variations in Mars’ gravitational field. Using a technique developed by Berne called “tidal tomography” that also takes into account the Sun’s varying gravitational influence on Mars as the Red Planet moves around its elliptical orbit, he and his team were able to infer a model of Mars’ interior structure and temperature. The way the gravitational field experienced by different spacecraft changed over time differs substantially from what would be expected if the interior of Mars were perfectly spherically symmetrical. To explain this difference, the mantle under Mars’ southern hemisphere must be between 390 and 750 degrees Fahrenheit (200 and 400 degrees Celsius) warmer than the northern mantle, and in fact, it is so warm that it could still be partially molten. This could have repercussions on both the habitability of Mars and the length of time it remained volcanically active. You may be interested Perhaps we should not be surprised that the interior of Mars is different in the south compared to the north, because we already know that its surface is asymmetric. The north of Mars is characterized by low plains, while the planet’s crust in the south is on average 25 kilometers (15.5 miles) thicker than in the north and is covered by cratered highlands. The northern lowlands may have once been home to a large ocean. “Understanding the dichotomy we see between north and south is important because it provides insight into processes that may have influenced the hydrology of Mars, including the formation of basins that may have retained water,” said Caltech’s Amirhossein Bagheri, second author of the research. An aerial view of wind-blown dunes in Kaiser Crater, a 207-kilometer-wide (129-mile) impact basin in the southern highlands of Mars. (Image credit: ESA/DLR/FU Berlin) A warmer southern mantle could also explain other puzzling discoveries on Mars. NASA’s InSight lander, which ended its mission in December 2022 and had a seismometer on board, found that seismic waves dissipate more quickly in the south, which can be explained by the higher temperatures there. Additionally, magnetic anomalies found in iron-bearing minerals in the south now make more sense. Today, Mars lacks a global magnetic field, but more than four billion years ago it had one. If the upwelling of a warmer southern mantle heated the crust above the ‘Curie temperature’, which is the temperature at which materials lose their inherent magnetic properties and any residual magnetism is induced in them, it could have resulted in the creation of mysterious magnetic traces in iron-bearing minerals. “Understanding the interior structure of planetary bodies helps us unravel the processes that shaped their formation and evolution,” Berne said, although the origin of Mars’ north-south divide is still a mystery. the air. It is not even clear whether superficial differences have the same causes as internal differences. What to read next A false-color map of the Martian surface showing the Hellas Basin, the large dark blue region beneath the center, one of the largest impact craters identified both on Mars and within the solar system. It is believed to have formed about 4 billion years ago. (Image credit: ESA/MOLA Science Team) The main argument is that it is all the result of a giant ancient impact more than four billion years ago and that the northern lowlands are therefore actually one huge impact basin. By opening a huge hole in the north, the impact would have facilitated the release of a large amount of internal heat, allowing the northern mantle to cool faster than the southern one. Alternatively, the thicker crust in the south could have proven to be an efficient lid, preventing much heat from leaking out of the mantle. This can actually be proven: magma upwelling would have stopped upon encountering the thick, dense crust, creating melted intrusions beneath the surface that could be inferred in higher resolution gravity data. These are questions for future missions, but the tidal tomography technique could also be used on other worlds, from Mercury to the large moons of Jupiter. “As we obtain more gravity data, we will be able to determine the three-dimensional complexities of a planet’s interior structure,” Berne said. “These inferences, in turn, give us a model for designing future missions and scientific exploration of these worlds.” The discovery of the Mars thermal anomaly was reported August 27 in Nature.
