29ers.com extends the familiar Colorado class system to the rest of the solar system.
The classes
- Class 1 — a walk-up. On this list, only the road up Mauna Kea.
- Class 2–3 — steep hiking and scrambling. Everest lives here.
- Class 4–5 — exposed climbing; ropes advisable.
- Class 6 — spacecraft and a pressure suit required. Vacuum, radiation, and −190°F. Every off-world route on this site.
Why Class 6?
No Colorado peak needs life support; every 29er beyond Earth does. Class 6 simply admits that the crux is getting there alive.
