Terraforming Mars Ares Expedition reduces the game to its essential card drafting and track advancement core. Each round you play action cards simultaneously, then resolve effects. The generation structure is replaced by fixed rounds. The result is faster, tighter, and less variable than the original.

The trade-off is most of what makes Terraforming Mars distinctive. The table presence is gone. The tile placement that gives Mars its physical shape is gone. The corporation depth that rewards replaying the same corporation differently is compressed. What remains is clean but thinner.

My recommendation: if your group loves the Terraforming Mars theme and finds the original too long, try Ares Expedition. If your group loves what the original game is — the full engine building experience with tile placement and corporation depth — Ares Expedition will feel like a shadow of it.