"Martians are invading!"
| The Martian Probe before spotting the player (left) and after (right). If the Probe is able to escape after detecting the player, the event begins.
Martian Madness is a Hardmode, post-Golem invasion-style event that includes several alien-themed enemies. It can be triggered only after Golem has been defeated.
Martian Madness is triggered by a Martian Probe, which spawns randomly in the two outer thirds of the map horizontally (with a higher spawn chance in the Space layer). When this small flying enemy detects a player or is attacked, it immediately attempts to fly away. If the Probe is allowed to escape without being destroyed by players, the Martian Madness event begins.
Once triggered, the status message "Martians are invading!" appears, and UFOs start flying in the background (see preview Banner); though Martian Madness enemies will not actually begin spawning until the player is located near the default spawn point or near an NPC with valid housing. As with other invasion-style events, a progress bar is shown in the bottom right corner while the event is ongoing. This bar fills as event enemies are defeated. When it reaches 100%, the event ends and new Martian enemies stop spawning.
| Martian Madness progress bar icon
|| Tin-Foil Hatter • "Triumph over a martian invasion, when beings from out of this world come to scramble your brains and probe you in uncomfortable places."
| Defeat the martian invasion for the first time.
- Martian Madness seems to be the rarest event in Terraria, because it is the only invasion event that cannot be summoned manually and Martian Probe will not spawn in center third of map where most players create their base.
- A Martian Probe will not spawn if the Lunar Events are active, if a Martian Madness event is already started, or if another Martian Probe is currently already present anywhere in the world.
- Playing in Expert mode does not increase the drop rate of Martian Madness items.
- It is possible to override Martian Madness with the Pumpkin Moon, Frost Moon, or other events.
- Exiting the world just before the Probe despawns may prevent the event from occurring when it is re-entered.
- You may want to avoid killing smaller enemies to allow more Martian Saucers to spawn during one event, as it has the most valuable drops. Moving to a small arena high enough above the ground makes it easier to ensure no ground-based enemies spawn around you.
- While most Minions will not deliberately target the Martian Probe, some can still accidentally kill it before it has the chance to detect players and escape, preventing the event from triggering. Minions should be dismissed if the player is trying to cause an invasion to occur.
- By using two portals or teleporters placed about 1000 feet apart you can quickly despawn regular invasion enemies without progressing the event, giving Martian Saucer more chances to spawn.
- The Tesla Turret is based upon the Tesla Coils, invented by Nikola Tesla, which can look similar and are often used to generate arcing electrical discharges ("artificial lightning").
- The Martian Walker is a reference to the tripod-like Fighting Machines from H.G. Wells' novel The War of the Worlds.
- Unlike most other enemies in the game, Martians have purple blood when killed rather than red.
- The achievement says "...comes down to scramble your brains and probe you in uncomfortable places.." The probing might be a reference to South Park; the aliens in the show would probe you through your anus.