Masked tectonic structures suggest Mercury contracted 40% more than its visible scars alone indicate

• The study led by Hokkaido University suggests that Mercury has contracted by about 10% to 30% more than previously thought.
• The researchers found that the planet's rough surface may have obscured some of the tectonic structures used to estimate shrinkage.
• The findings were published in *Geophysical Research Letters*.

• The study compared global maps of Mercury's surface roughness with shortening structures and contraction.
• After accounting for the effect of rough terrain, the estimated radial contraction increased from 8.3 km to 11.6 km.
• The researchers suggest that this figure may still be an underestimate and that the actual contraction could be greater.

• The findings provide new insights into Mercury's geological evolution.
• Future observations from BepiColombo may help refine the picture further.
• The BepiColombo Laser Altimeter, or BELA, will measure surface roughness at much finer scales and could reveal relationships between much younger geological events and tectonic structures.
• The same effect could also be relevant on other rocky worlds, particularly the moon.

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