"CHAINSPLIT!"
It's a rim howler, alright. It's not just a distant, ghostly, undifferentiated whine anymore. He can hear the regular scooping of the thing's initial roar through his space helmet. The wall has to be right in front of him now, just beyond where this mustard fog is thickest.
He makes his steps very small, so the low gravity will not give him so much 'bounce'. This allows him to detect the rise of the ground, since he can't see a thing through this blizzard. There is an upward slope, and its incline is increasing. Good.
He swings his arms around but finds nothing. Did he miss the mark? Bringing up the blipfinder on the back of his space mitt, he brushes the accumulated yellow dust off the bezel of its screen. Just a weeee bit to the right.
"Leon, do you read?" blares the snoopset in his helmet once again. Meanwhile, glove strikes ladder -- exactly what he was panning for. He grips it, and starts to climb.
Leon says, "I'm here."
(snoopset) "There is a chainsplit. Over."
Leon says, "Which chain?"
(snoopset) "Like I know..."
Leon says, "Well, look!"
(snoopset) "It's just blinking 'CHAINSPLIT' exclamation mark."
Leon says, "... It shouldn't really be blinking."
(snoopset) "Want me to send video?"
Leon says, "Nah. Anything in the scrolls?"
(snoopset) "Don't think so. Scrolling..."
Cresting the top of the ladder, pulling himself over, out of the mists, and onto the rim -- yellow splashing off him as his space joints move -- Leon's hit smack in the visor by the big blue ball of the Earth. Every time he climbs out of the dustbowl, he imagines he's a half-drowned flea dragging itself from a pea soup, witnessed by that unhappy blue-grey eye. He can no longer hear the howler howling -- there just isn't enough mist at this altitude to communicate the vibrations to his space suit.
He spots the Protopod facility, probably over 1000 feet away along the crater's rim. He's come up much farther away than he expected. Unable to resist curiosity, he keeps a hand on the ladder head, and leans back, searching against the starry background behind the limb of the Earth, but of course, sees nothing there with the naked eye. And then he does just what they tell you never to try to do, out here. (It's in the fucking manual.) He starts to run...
Good one