Researchers have discovered a significant temperature imbalance deep inside Mars, with the planet’s southern interior estimated to be 200 to 400 degrees Celsius hotter than its northern half.
Gravity measurements suggest that the underground interior of Mars’ southern hemisphere is considerably warmer than the north and may be partially molten. The findings offer new insights into Mars’ geological history, including when the Red Planet may have had conditions capable of supporting life.
The study was led by Alexander Byrne (Ph.D. 26), a Caltech alumnus and postdoctoral fellow at the University of Arizona. The research was published on August 27 in Nature.
Mapping Mars’ interior through gravity
During his graduate studies at the California Institute of Technology, Byrne developed a model that uses subtle variations in gravity to determine the internal structure of planetary bodies. He and his colleagues later applied the technique to Mars.
The researchers analyzed decades of data from three NASA Mars missions: Mars Global Surveyor, Mars Odyssey, and Mars Reconnaissance Orbiter. By measuring tiny changes in spacecraft velocity, the team reconstructed Mars’ gravitational field.
Mars follows a slightly elliptical orbit and rotates on an inclined axis, causing the Sun’s gravitational influence on the planet to vary throughout the year. The researchers used a technique called tidal tomography to examine these changing gravitational signals and create a detailed model of Mars’ interior.
“Scientists usually assume that the interiors of planetary bodies are generally spherically symmetric, but this is not necessarily true,” Byrne says. “As we acquire more gravity data, we can determine the three-dimensional complexity of a planet’s internal structure. These findings provide a blueprint for future missions and scientific exploration. Understanding planetary interiors helps reveal the processes that shaped their formation and evolution.”
A major north-south divide beneath Mars’ surface
Mars has long been recognized for the striking contrast between its two hemispheres. The southern surface is dominated by highlands and heavily cratered terrain, while the northern hemisphere consists largely of broad, low-lying plains.
The new study suggests that this north-south divide extends deep beneath Mars’ surface. Researchers found that the planet’s interior is also thermally heterogeneous, with the southern interior several hundred degrees warmer than the north.
This hidden heat could help explain several other unusual characteristics of Mars.
Scientists have identified distinctive magnetic signatures in iron-rich minerals across the Southern Hemisphere. The hotter southern mantle may indicate that Mars once had a global magnetic field strong enough to produce differences in magnetization between the planet’s two hemispheres.
NASA’s InSight mission also found that seismic waves lose energy more rapidly in the southern region. The newly identified high temperatures may help explain this difference in seismic behavior.
Temperature clues about Mars’ watery past
“The dichotomy between north and south is important to understand because it provides information about processes that may have influenced Mars’ hydrology, including the formation of basins that could have stored water,” says Amirhossein Bagheri, a postdoctoral researcher at the California Institute of Technology and co-author of the study. Bagheri is also a former member of the InSight team.
Understanding the temperature differences inside Mars could provide new clues about how the planet evolved and how its topography formed during periods when liquid water may have existed on the surface.
Researchers do not yet know what caused the thermal anomaly. Several explanations are being considered.
One possibility is that a massive impact generated heat in the northern region. Another hypothesis suggests that convection may once have occurred spontaneously in Mars’ southern mantle. A third possibility is that thick geological structures in the south trapped heat and prevented it from escaping efficiently.
A new view of Mars’ deep interior
The paper is titled “Tidal Tomography Reveals Thermal Anomalies Underlying Mars’ Crustal Dichotomy.”
In addition to Byrne and Bagheri, the co-authors include Nicholas Wagner and Harriet Lau of Brown University; Isamu Matsuyama and Angela Marciak of the University of Arizona; Sander Goossens of NASA’s Goddard Space Flight Center; Kar-wai Chen of the Institute of Astronomy and Astrophysics at Academia Sinica in Taiwan; Antonio Genova of the University of Rome in Italy; Marc Rovira-Navarro of Delft University of Technology in the Netherlands; Chuan Qin of UCLA; Douglas Hemingway of the University of Texas at Austin; Shijie Zhong of the University of Colorado Boulder; and Francis Nimmo of the University of California, Santa Cruz.
The research was funded by NASA.
Source: www.sciencedaily.com