Skip to content

THE 42 INDEX

Public index · Planetary

Mercury · outer shell

~420 km

Measured

Hauck et al. 2013: Mercury’s solid outer shell 420 ± 30 km thick (crust and mantle, possibly a solid outer core).

Mercury’s metallic core leaves a thin silicate shell. MESSENGER gravity and spin put that outer shell near 420 km, with a 30 km uncertainty. NASA’s public facts page rounds the same structure to about 400 km.

Documentary plate

Mercury in true color from MESSENGER. A large metallic world with a thin silicate shell.

NASA / Johns Hopkins APL / Carnegie Institution of Washington. MESSENGER true-color mosaic.

What it supports

A model-dependent physical estimate from MESSENGER geodesy. The 420 is a published fit, not an invariant of the planet.

What it does not

Not an exact 420 km crust. Not the same object as Sacajawea’s 420 km frame or Mars’s polar cap. NASA facts still say about 400 km.

Calculation

420 ± 30 km (Si-bearing core ensembles). NASA facts: ~400 km.

ExactnessApproximate

Form420

Unitkm

Strengthhard

Source

Hauck et al. 2013, JGR Planets · outer shell 420 ± 30 km

Owner

Planetai