Researchers Found Mercury Shrunk 23 Kilometers
A new study reveals that the planet Mercury has contracted significantly more than earlier research suggested.
Updated on Sept. 21, 2026 in Space
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Scientific findings published in Geophysical Research Letters indicate that Mercury has experienced a diameter reduction of 23 kilometers. This contraction is attributed to the long-term cooling of the planet's core.
Why it matters
Understanding the cooling process of Mercury's interior provides critical insights into the geological evolution of rocky planets. This study confirms that crustal compression is more widespread than previously understood.
Researchers utilized data to observe that crustal ridges formed as the planetary core cooled, causing the surface to buckle. This contraction stands in contrast to the 2013 estimate of only 11 km of shrinkage.
The players
Geophysical Research Letters
This is a peer-reviewed scientific journal that publishes high-impact reports on the Earth and space sciences.
BepiColombo
This is a joint mission between the European Space Agency and the Japan Aerospace Exploration Agency to study Mercury.
Messenger
This was a NASA space probe that performed the first orbital study of Mercury between 2011 and 2015.
The details
The cooling of the planet's core causes the crust to buckle and thrust, which in turn creates giant curved cliffs known as wrinkles. By identifying a greater number of these crustal ridges, scientists have updated the total shrinkage calculation for the planet.
Timeline
Mariner 10 reached Mercury in the 1970s.
The Messenger probe orbited the planet from 2011 to 2015.
An earlier shrinkage estimate of 11 km was produced in 2013.
BepiColombo is scheduled to enter Mercury's orbit in December 2026.
The Big Picture
This study precedes the arrival of the BepiColombo mission, which is expected to provide higher resolution data on surface features. These findings challenge previous geological models and establish a new baseline for planetary contraction research.
This research enhances our fundamental understanding of how rocky planets evolve and stabilize over billions of years. These insights provide a broader context for the study of other celestial bodies, such as Mars and the Moon, which may have experienced similar cooling processes.
The takeaway
Mercury's physical size is a direct reflection of its internal cooling history over time. By mapping surface wrinkles, scientists can better reconstruct the life cycle of planets in our solar system.
What happens next
The BepiColombo mission is scheduled to enter Mercury's orbit in December 2026, which will allow researchers to collect more detailed data on the planet's geological structure.
Further reading
For more information on planetary exploration, visit our Space section.
Live Poll
Does learning about planetary cooling change how you view the long-term future of our solar system?
