Scientists from the German Aerospace Center’s Institute of Space Research announced Thursday that the planet Mercury may be shrinking faster than previously believed. Their calculations suggest a loss of up to 14 miles (23 kilometers) in diameter – roughly a 30% increase over earlier estimates.
Why the planet is contracting
Mercury’s hot iron core, oversized for its small size, has been cooling and contracting since the planet formed 4.5 billion years ago. As the core and mantle shrink, the surface tightens like a belt, creating visible “wrinkles” that scientists use to measure the planet’s size.
New method reveals hidden loss
The research team, led by Dr. Gaku Nishiyama of Hokkaido University, compared traditional fault‑line maps with newer maps that highlight surface roughness. They found that the roughest regions showed fewer contraction wrinkles, suggesting that impact debris may be covering the true extent of the shrinkage.
By accounting for these obscured areas, the team arrived at a revised shrinkage estimate that could reshape our understanding of how small, rocky worlds evolve over time.
BepiColombo mission to confirm findings
The European‑Japanese BepiColombo spacecraft, currently on its way to Mercury, carries a laser altimeter designed to measure the planet’s topography with unprecedented precision. The probe is expected to enter Mercury’s orbit in November and will soon separate into two components for a detailed survey.
“We are quite excited,” Nishiyama said in an email, adding that the mission’s data will help verify the new shrinkage calculations and improve models of planetary cooling.
Historical context
Only two spacecraft have ever visited Mercury: NASA’s Mariner 10 in the 1970s and the Messenger probe in the 2010s. Messenger’s measurements formed the basis of earlier shrinkage estimates. The new analysis suggests that those figures may have been conservative because they did not fully consider surface roughness and debris coverage.
Understanding Mercury’s contraction not only informs planetary science but also offers clues about other small, cooling worlds throughout the solar system.
What’s next
When BepiColombo begins its detailed mapping, scientists will compare its laser data with the roughness‑adjusted models. If the spacecraft confirms a larger diameter loss, it could prompt a reassessment of thermal evolution models for Mercury and similar planets.
For now, the study highlights how even well‑studied bodies like Mercury can still surprise researchers, reminding us that the cosmos continues to reveal new mysteries.
Original reporting: Alexandria, VA News – WTOP News — read the source article.
