Scientists believe they have solved the 50-year-old mystery surrounding the Martian dichotomy. This dichotomy is the geological contrast between Mars’s southern highlands and northern lowlands. The research team believes NASA’s InSight lander has solved the mystery, suggesting the contrast is caused by internal planetary processes. The findings were published in the peer-reviewed journal, Geophysical Research Letters.
This would be quite different from the previous hypothesis that suggested the contrast was caused by cosmic collisions, like asteroids and meteors.
The research team focused their analysis on ‘marsquakes’. The data collected suggests the divide may have likely been shaped by heat transfer deep within the red planet.
The Martian dichotomy was first discovered in the 1970’s
When the Viking probe returned extremely detailed images of the red planet in the 1970s, scientists quickly pointed out the contrast between north and southern Mars, thus discovering the ‘Martian dichotomy.’ The initial images revealed that Mars’ southern highlands rose four miles higher than the smoother northern lowlands.
It was also determined that the highlands were quite ancient, dating back to when Mars had a global magnetic field. In contrast, the northern highlands are ‘younger’. We know this because they lack magnetization, and have fewer craters.
Two hypotheses were proposed at the time of the Martian dichotomy’s discovery. The first one was the endogenic hypothesis, which suggested internal planetary forces, such as the transfer of heat and mantle dynamics, shaped Mars’ surface. Conversely, the exogenic hypothesis suggests the differences on Mars’ surface are due to collisions with moon-sized and other smaller objects.
Article: The Martian dichotomy boundary receded hundreds of km in the Mawrth Vallis region and left behind mounds that record changing aqueous conditions during the Noachian@Joseph_McNeil @DrPFawdon @Mattbalme @NHM_Londonhttps://t.co/51YbRY150q pic.twitter.com/ArUfKerqf6
— Nature Geoscience (@NatureGeosci) January 20, 2025
Scientists found that seismic waves they sent down the planet’s surface using InSight’s seismometer showed that the waves in the highlands lost energy quicker than those in the northern lowlands. This indicates that the rock beneath the highlands is much hotter than the rock in the north of Mars.
The mystery Is only partially solved
In their study, the authors noted that these findings, supported by geochemical analysis of Martian meteorites, provide valuable seismological observations that support the ‘endogenic’ hypothesis, suggesting that mantle convection plays a crucial role in forming the Martian crustal dichotomy.”
However, the Martian Dichotomy mystery is only partially solved. The researchers also noted that more marsquake data and observation are needed to confirm the findings.
A new image from ESA’s Mars Express shows a continuous strip of the planet, from its cloudy northern polar region to Hellas Planitia in the south. Notice the difference in terrain types between the Southern and Northern hemispheres — this is known as the Martian dichotomy. pic.twitter.com/0PKrmb6u6F
— Jack William Skinner (@jackatmos) September 24, 2019
This new analysis will also be compared to studies of Earth, Mars, and other planetary bodies with similar phenomenons on their surface, to conclude what’s behind the Martian dichotomy.
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