--- title: "Mercury Is Shrinking 30% Faster Than Scientists Thought: The Planet's Diameter Has Decreased by 23 Kilometers" description: "German scientists recalculated the data and found that Mercury's diameter has decreased by 23 kilometers — 30% more than previous estimates. The exact picture will be confirmed by the BepiColombo mission." date: 2026-09-13T07:06:26.000Z lang: en url: https://xab.info/en/posts/mercury-shrinking-faster-than-expected-diameter-decreased-by-23-km tags: [mercury, solar-system, planetary-science, bepicolombo, space-research] publisher: "XAB.info" --- # Mercury Is Shrinking 30% Faster Than Scientists Thought: The Planet's Diameter Has Decreased by 23 Kilometers ![The planet Mercury with its cratered surface against the starry sky — a visualization of the contraction that has reduced the planet's diameter by 23 kilometers](https://xab.info/media/2026/09/13/merkuriy-szhimaetsya-bystree-chem-ozhidalos-diametr-umenshilsya-na-23-km/merkuriy-szhimaetsya-bystree-chem-ozhidalos-diametr-umenshilsya-na-23-km-1.webp) ## 🎯 Key Points - Mercury's diameter has decreased by 23 kilometers — 30% more than previously assumed. - The study was conducted by scientists at the Institute of Planetary Research of the German Aerospace Center (DLR). - The cause of the contraction is the cooling of the large iron core, which compresses the mantle and crust and creates folds and faults. - Meteorite bombardment may have hidden some signs of contraction beneath debris. - The precise level of contraction will be confirmed by the BepiColombo mission spacecraft, expected in orbit in November 2026. The smallest planet in the Solar System and the one closest to the Sun continues to "shrink" — and, according to new estimates, noticeably faster than previously assumed. Scientists at the Institute of Planetary Research of the German Aerospace Center (DLR) have concluded that Mercury's diameter has decreased by 23 kilometers over the course of its existence, which is 30% higher than previous calculations. The results of the study, reported through the Associated Press, revise our understanding of how quickly the planet is losing volume as its interior cools. ### Shrinking by 23 Kilometers: What Exactly Did the Researchers Recalculate The key update concerns the scale of global contraction. If earlier models yielded a smaller magnitude of shrinkage, the new methodology, based on comparing Mercury's geological maps with updated maps of its surface, showed that the planet has "contracted" by 23 kilometers. The authors emphasize that the constant alteration of the surface due to meteorite impacts may have masked the true level of contraction: on the most rugged sections, signs of contraction turned out to be fewer than expected, and some of the folds, they suggest, were hidden beneath debris formed by meteorite falls. ### Why the Planet Is Getting Smaller: A Cooling Iron Core The cause of the process lies in Mercury's thermal evolution. Since its formation about 4.5 billion years ago, the planet has been gradually cooling. As the relatively large iron core cools, it shrinks in volume, which in turn leads to the compression of the mantle and crust. It is precisely this compression that creates the characteristic folds and faults on the surface, which serve as "imprints" of the planet's internal contraction. Thus, the visible geological structures become direct evidence of how Mercury has been losing volume over billions of years. ### Methodology and Significance of the New Calculations The researchers did not limit themselves to direct measurements: they compared Mercury's geological maps with updated surface maps and analyzed the distribution of contraction features across sections with varying degrees of terrain "roughness." This approach allowed them to account for the distorting factor of meteorite bombardment. The study's author, Gaku Nishiyama, stated that the new calculations will help better understand Mercury's evolution as a whole — from the dynamics of core cooling to the formation of surface structures, which is important for modeling similar processes on other planets with large iron cores. ### Field Verification: The BepiColombo Mission The estimates obtained on Earth are yet to be confirmed directly at the planet. Spacecraft from the BepiColombo mission, jointly implemented by Europe and Japan, are currently en route to Mercury. They are expected to enter the planet's orbit in November 2026 and begin direct study of its surface and internal structure, which will allow the precise level of Mercury's contraction to be refined and compared with the results of ground-based calculations. This will make the mission an important tool for validating the new model of the planet's shrinkage. ### Background: What Is Known About Mercury Mercury is the smallest planet in the Solar System, with a diameter of about 4,900 kilometers. It completes one orbit around the Sun in 88 days, while a single solar day on the planet lasts approximately 59 Earth days. Due to its extremely thin atmosphere, temperature fluctuations on the surface are extreme: daytime temperatures can rise to 430 degrees Celsius, while nighttime temperatures can drop to minus 180 degrees. It is precisely the combination of proximity to the Sun, a large iron core, and the absence of a dense atmosphere that makes Mercury a unique object for studying the thermal and geological evolution of planets. ## 🔍 Fact-Check Verification - [Mercury Is Shrinking Faster Than Expected: Scientists Establish a New Fact – Zamin.uz, 12.09.2026](https://zamin.uz/ru/mir/221059-merkuriy-szhimaetsya-bystree-chem-ozhidalos-uchenye-ustanovili-novyy-fakt.html) - Подтверждает ускоренное сжатие Меркурия и пересмотр оценок; дата публикации 12.09.2026 согласуется с актуальной датой. - [The Smallest Planet in the Solar System: How Much Has Mercury Shrunk and Why (Photos)](https://focus.ua/technologies/720002-merkuriy-umenshaetsya-v-razmerah-chto-proishodit-s-planetoy-foto) - Согласуется с базовым текстом по масштабу уменьшения и причинам (остывание ядра); расхождений в цифрах с основным источником не обнаружено. ## ❓ FAQ ### Q: By how much has Mercury shrunk, according to the new data? **A:** According to calculations by DLR scientists, Mercury's diameter has decreased by 23 kilometers, which is 30% more than previous estimates. ### Q: Why is the planet shrinking? **A:** The cause is the cooling of the large iron core: as it cools, it shrinks in volume, which compresses the mantle and crust and creates folds and faults on the surface. ### Q: Who conducted the study and how will it be verified? **A:** The work was carried out by scientists at the Institute of Planetary Research of the German Aerospace Center; the precise level of contraction will be confirmed by the BepiColombo mission spacecraft, expected in Mercury's orbit in November 2026.