Venus has a thinner lithosphere in the north. That side also contains more than twice as many volcanoes. Researchers say the difference changes how the planet releases internal heat.
NASA's Magellan probe provided the gravity and topography data for a new study of Venus. The research found that the planet's northern lithosphere is thinner and contains more than twice as many volcanoes as the southern region.
The finding offers a new explanation for how Venus loses internal heat. The planet has no plate tectonics like Earth's system for recycling lithosphere.
The volcanic imbalance is the study's basic finding.
Researchers from the Universidad Complutense de Madrid and the Universidad Rey Juan Carlos linked the thickness of the rigid outer layer to the number of volcanic structures across the planet. Their work was published in Earth and Planetary Science Letters.
Europa Press reported that the international team read the north-south contrast as a planetary-scale result, extending beyond an isolated geological anomaly. A thinner lithosphere lets more heat from the interior reach the surface through volcanic activity.
That fits the higher concentration of volcanoes in the north. Venus is close to Earth in size, but its geological history took a different path because it has no equivalent of Earth's recycled lithospheric plates.
Researchers had not identified this distinction beyond a well-known volcanic zone.
Scientists already recognised the BAT anomaly, named for the elevated volcanic regions Beta, Atla and Themis, where volcanoes are unusually concentrated.
The new result concerns the rest of Venus. Beyond BAT, the northern and southern hemispheres show statistically different patterns instead of following one common pattern.
Using gravity and topography data from NASA's Magellan probe, the team reconstructed the lithosphere. Magellan launched in 1989 and orbited Venus for four years.
Researchers matched those measurements with a map that divided the surface into geological provinces. They then used statistical methods to test whether the regional contrast was impressive.
The data connect three elements that had largely been considered separately: lithospheric thickness, volcanic distribution and the planet's internal cooling.
The research was led by Ignacio Romeo Briones. Marina Mendiburu-Eliçabe contributed the statistical analysis. Alberto Jiménez Díaz worked on the geological and geophysical modelling at the Universidad Rey Juan Carlos.
The approach puts the north-south contrast at the centre of the explanation. It treats the difference as a planetary feature, not one limited to BAT.
That distinction matters.
Venus cannot be understood as a larger version of a tectonically active Earth. Its heat escapes through a surface whose properties differ between hemispheres, and the volcanic count reflects part of that uneven structure.
For researchers studying planetary interiors, the contrast says more than the raw number of volcanoes. It identifies a physical difference that models of Venus must reproduce.
The study does not establish why the lithosphere became thicker in the south or thinner in the north. Javier Ruiz said the researchers are considering different hypotheses, but stressed that no single explanation exists for the contrast.
The measurement is clear. Its cause is not.
Compared with the financial indicators discussed in an earlier report, the Venus result has no immediate household effect. It does carry a precise scientific consequence.
The evidence changes how scientists interpret the planet's geological history. Any credible model must account for unequal lithospheric thickness across Venus and for the way that difference controls volcanic heat release.
Venus's north and south differ in more than appearance; the regions operate under distinct geological conditions.
