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yesterday

Mercury's Shrinkage Revised Upward After Study Finds Craters Hide Tectonic Faults

Surface roughness and impact ejecta mask contractional landforms, with upcoming BepiColombo altimetry set to test the revision.

NASA / Futurism
(Image Source: Adobe Stock Image)
The MESSENGER spacecraft captured this view of Mercury in 2008. Scientists have long known Mercury is shrinking. But now they say it has shrunk up to 30% more than they thought. Image via NASA/ Johns Hopkins University Applied Physics Laboratory/ Carnegie Institution of Washington.
This color image of Mercury was generated from three MESSENGER images taken through filters sensitive to light in different wavelengths. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington.

Overview

  • A peer-reviewed paper led by Gaku Nishiyama used MESSENGER topography and a global roughness map to correct tectonic counts and raised Mercury's best estimate of radius loss to about 11.6 kilometers.
  • The authors show that heavily cratered, rough regions systematically hide lobate scarps and wrinkle ridges, which likely caused prior studies to undercount contraction by roughly 10% to 30%.
  • A larger inferred contraction tightens constraints on Mercury's thermal and interior evolution and favors models with a larger metal core and a thinner insulating regolith.
  • The team cautions the corrected figure is likely a lower bound and says ESA–JAXA's BepiColombo laser altimeter, with much finer (≈100 m) topography, will be decisive for confirming and refining the result.
  • The study's method could expose similar undercounts on other cratered worlds, notably the Moon and possibly Mars, prompting reassessments of planetary cooling histories.