[MISSION] Tywom parts? [SOLVED]

This has got to be the dumbest question I've ever asked. Looks like I'm the first in the world to ask it, which means everyone else already knows the answer.

So yeah, can't find two of the Tywom ship parts.

I've found one of the ship parts and the following:

Lexite ruins, Soviet probe, Alien monument, Crashed Tesla

Apparently I can't land on:

Mercury, Venus, Mars, Io, Titan, Enceladus, Elpis

I don't remember if any of those bodies have artifacts on them or not.

What am I missing?

[SOLVED]

I figured out you can steer on your way down.