Sweep The Moon events

What does the Meteor Merchant sell?

The merchant arrives with an announcement and stays 240 seconds. The reward line says robots and drones for Cash or Robux. That matches the owner-payout robots and the Mothership Drone on the robots page, but the event row does not repeat each price. Use the robot table for numbers and this page for the timer. If you miss the window, the page does not say the stock returns on a clock.

UFO, raids, delivery, arcade

The UFO event starts with a landing announcement and a green beam. It lasts until the chest opens, plus 10 seconds. The reward is alien treasure, and an Alien Robot is possible. Goblin Raid is a warning, then goblins until they retreat, and the stake is Dust, Cash, and machines. Express Delivery is a crash announcement and supply crates that can contain Cash. Arcade appears near the base, pays Cash by minigame score, and leaves on a countdown. The Event Shop is a sign with its own closing countdown. All of these rows are one source.

I would stop sweeping and open the UFO chest when the beam is up, because the row gives a short tail after the chest opens. I would not chase a goblin raid with a half-full canister if the warning says they take Dust, but that is a reading of one sentence, not a clip I timed.