So far, I've identified these important parts of an exploration game:
Goal - All expeditions have goals. They aren't formed without reason. A goal represents the "win" of the scenario. This is good for the players and the game. This changes with each expedition, so the players always get new win criteria, keeping the game interesting. The goal of an expedition is usually knowledge.
Budget - All exploration requires a budget. That's how much money that you need to spend in order to achieve your goal. In some theoretical universe, you may have unlimited funds, but most of the time funds are limited. This provides a constraint to the players and that's a good thing for the game.
Planning - Expeditions don't just happen. They have to plan out what they want to achieve and how they want to achieve it. There's no right or wrong answer here, but if you don't get there, you don't get there. If everything goes well, your plans make your expedition a success. If you plan wrong, or there are changes in circumstances, plans go awry. In the absence of perfect information, planners eventually make assumptions that prove incorrect. That's a good thing for a game.
Recruitment - Each unique expedition requires information and skills that the planners do not have, from animal handlers, to servants, to guides. People are the key to making any expedition work. The exact needs of people vary by expedition.
Execution - This is the traditional "interesting part" of the role playing game. The players must actually make the expedition work to achieve its stated goal. This will never be the same twice and never quite be what the players expect.
Report - The ultimate goal of any expedition is the acquisition of new knowledge. What was learned? A written report is very important, so the players will need to create a written report of some kind detailing what was learned. A report can be a travel log, newspaper stories by an embedded reporter, academic papers, formal reports to investors, source book entries for locations, or some other sort of formal presentation.
There may yet be more bullet points before I'm done.
If I am to correctly design an exploration game, these areas must be of competing concern to the players. The vast majority of time must be split between these areas. That means that if the players spend many sessions planning, few sessions exploring, and many sessions forming a report, then the game is working as intended. Indeed, all those details are the game.
Ivory RPG - A Hypothetical Pure Exploration RPG