Since node IDs are random, node lookup may require multiple interplanetary hops, no?
For instance, from N1 on Earth to the nearest XORwise node in its routing table which might be N2 on Mars, whose routing table finds the target node N3 on Earth.
We do use Kademlia - but note this release actually runs 2 DHTs - one for LAN connections and one for WAN connections. You could easily imagine a small Mars outpost as the LAN DHT where you can do fast retrieval for all content already available locally without hitting interplanetary lookup times.
In an actual interplanetary setup, we would definitely not be using a single DHT across the entire space. The main idea once we get to that scale is either a different content routing system altogether, or sharded coral style DHTs (https://en.wikipedia.org/wiki/Coral_Content_Distribution_Net...)
