outermost

the outermost layer of the earth.

the orbit of the outermost of these eight planets.

the outermost atmospheric layer

Last is the exosphere, which is the outermost layer of the atmosphere.

The term epiblem is sometimes used instead to denote the outermost layer of cells in the root.

Bark The outermost tissue of the stem and roots in woody plants, on the outside of the phellogen (cork cambium).

New Horizons' trailblazing journey to the solar system's outermost frontier took it past the orbit of Mars today at 6 a.m. EDT , 78 days after the spacecraft launched.

Exodermis An outermost layer of thickened or suberized cortical cells that sometimes replaces the epidermal layer in the older parts of roots if the epidermal cells have died.