Even with all we\u2019ve learned about Mars in recent decades, the planet is still mysterious. Most of the mystery revolves around life and whether the planet ever supported any. But the planet teases us with more foundational mysteries, too. <\/p>\n
One of those mysteries is the Martian dichotomy: Why are the planet\u2019s northern and southern hemispheres so different?<\/p>\n
<\/p>\n For some reason, Mars\u2019 southern hemisphere is predominantly highlands and has a higher elevation than the northern hemisphere\u2014about 5km (3 mi) higher. The south also has a thicker crust, is older and is covered in craters. <\/p>\n The northern hemisphere is a vast, smooth plain with a thinner crust and fewer craters. It is also less magnetized than the south. <\/p>\n Scientists have been puzzling over this dichotomy and have proposed different reasons for it. One leading theory involves a massive impact. Some researchers using geophysical modelling have suggested that a Pluto-sized body struck Mars early in its history. The impact could\u2019ve created the northern lowlands as a gigantic impact basin. <\/p>\n Other researchers have proposed that the planet\u2019s internal (endogenic) processes created the dichotomy. Plate tectonics or mantle convection could\u2019ve been behind it. <\/p>\n Either way, the dichotomy is fundamental to understanding Mars. We can\u2019t understand the planet\u2019s evolution without revealing the mystery behind the dichotomy. This is why NASA and the DLR launched the InSight lander, which reached the Martian surface in November 2018. <\/p>\n The lander\u2019s name stands for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport. Among its instruments was SEIS, the\u00a0Seismic Experiment for Interior Structure. SEIS helped scientists better understand Marsquakes by detecting and measuring hundreds of them. It also <\/span>helped them measure crustal thickness and investigate the mantle. InSight\u2019s data also helped them constrain the size of Mars\u2019 core. <\/p>\n Scientists are still working with InSight\u2019s data, and a new research letter published in the AGU\u2019s Geophysical Research Letters suggests that Mars\u2019 convection is behind the Martian dichotomy. It\u2019s titled \u201cConstraints on the Origin of the Martian Dichotomy From Southern Highlands Marsquakes.\u201d The authors are Weijia Sun from the Chinese Academy of Sciences and Professor and geophysicist Hrvoje Tkalcic from the Australian National University. <\/p>\n The authors state the Martian dichotomy in clear terms: \u201cThe Martian hemispheric dichotomy is delineated by significant differences in elevation and crustal thickness between the Northern Lowlands and Southern Highlands.\u201d The altitude difference is about equal to the height of the tallest mountains on Earth. <\/p>\n This research is based on a cluster of Marsquakes in the Terra Cimmeria region of the southern highlands. \u201cWe analysed waveform data from so-called low frequency marsquakes captured by NASA\u2019s InSight seismograph on Mars,\u201d Professor Tkalcic said. \u201cIn doing this, we located a cluster of six previously detected, but unlocated marsquakes in the planet\u2019s southern highlands, in the Terra Cimmeria region.\u201d<\/p>\n These quakes gave the researchers new seismic data from previously unstudied regions, which is significant because it allows them to compare the data to seismic data from other regions, especially from the Cerberus Fossae region in the northern lowlands. <\/p>\n Cerberus Fossae is a series of near-parallel fissures on Mars. Scientists think they were created by the Tharsis volcanoes to the east and Elysium to the west.<\/p>\n The researchers worked with InSight\u2019s seismic data and improved the signal-to-noise ratio. That improvement allowed them to pinpoint the locations of the marsquakes. \u201cHere, we improve the signal-to-noise ratios and determine the locations of the low-frequency marsquakes recorded during the InSight mission. We find a new cluster of marsquakes in Terra Cimmeria, Southern Highlands, in addition to those previously located in Cerberus Fossae, Northern Lowlands,\u201d they write. <\/p>\n The researchers used what\u2019s called the spectral ratio method to determine the quality of the waves. In this context, quality refers to how quickly seismic waves lose energy as they travel through the Martian interior. It\u2019s expressed as a value for \u2018Q\u2019 which was different between the Cerberus Fossae region and the Terra Cimmeria region. <\/p>\n \u201cUsing the spectral ratio method, we estimate the quality factor Q in the range 481\u2013543 for Terra Cimmeria versus 800\u20132,000 determined for Cerberus Fossae,\u201d the researchers explain. A higher Q in the Southern Highlands\u2019 Terra Cimmeria indicates that seismic waves there \u2018attenuate\u2019 or lose energy more quickly. <\/p>\n Such a large difference in Q between regions indicates that the subsurfaces are substantially different from one another. Temperature and mantle convection could be the key. \u201cThe attenuation difference might be linked to the temperature differences between the two hemispheres, along with more vigorous convection beneath the Southern Highlands,\u201d the paper states. <\/p>\n \u201cThe data from these marsquakes, when compared with the well-documented northern hemisphere marsquakes, reveal how the planet\u2019s southern hemisphere is significantly hotter compared to its northern hemisphere,\u201d Professor Tkalcic said. \u201cUnderstanding whether convection is taking place offers clues into how Mars has evolved into its current state over billions of years.\u201d<\/p>\n Researchers\u2019 primary goal in studying the Martian dichotomy has been to determine whether endogenic or exogenic processes or events are responsible. However, the impact theory is hampered by timing. There are significant geochronological constraints for giant impacts on Mars. Crater data, mineral distribution, and the presence of river channels all conflict with the impact hypothesis, which most researchers suggest had to have happened early in the Solar System\u2019s history. <\/p>\n \u201cThese seismological observations, together with geochronological constraints of giant impacts, reinforce the \u201cendogenic\u201d hypothesis that mantle convection causes the crustal dichotomy,\u201d they explain. <\/p>\n Are these findings a breakthrough in understanding the Martian dichotomy? Possibly. Compared to our seismic probings of Earth\u2019s interior, Mars is practically undiscovered. <\/p>\n \u201cOn Earth, we have thousands of seismic stations scattered around the planet. But on Mars, we have a single station, so the challenge is determining the location of these marsquakes when you have only a single instrument,\u201d Professor Tkalcic said. <\/p>\n It seems that the researchers have met that challenge. <\/p>\n \u201cThese findings, supported by geochemical analysis of Martian meteorites, provide valuable in situ seismological observations that support the \u201cendogenic\u201d hypothesis, suggesting that mantle convection plays a crucial role in forming the Martian crustal dichotomy,\u201d the authors explain.<\/p>\n![\"\"](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2025\/01\/1280px-Wikiterracimmeriaboundaries-1024x528.jpg\")
![\"The](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2025\/01\/Cerberus-Fossae-context-1024x403.jpg\")
![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2025\/01\/grl68726-fig-0001-m-938x1024.jpg\")
![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2025\/01\/grl68726-fig-0004-m-1024x643.jpg\")
Like this:<\/h3>\n