Everyone hates that flying piece of crap 505 kindly called, the Martian Saucer. It's very much very annoying and now we'll go into how to kill it with ease.
Guide to Beating Martian Saucer
How to Summon the Martian Saucer
Well, first you'll want to start the Martian Madness event by killing a Martian Probe (It will only summon after you beat Golem), then it has a chance of spawning during that, but has increased chances after it's reached 50% completion. To easily summon the Martian Madness event, first head to the ocean, get a water candle, battle potion, etc. that will increase enemy spawns, then build a space platform. It has the highest chance of spawning in space and near the ocean, so it's a guaranteed find. But whatever you do, Don't kill the Martian Probe, or else the event won't trigger.
How to Kill the Martian Saucer
Once the event has been triggered, make a big box about the size of an NPC room, but a little taller, and with no doors. If you add doors all the other little and miniscule creatures will come barging and screw up your plans. The reason you're making a box is so that the Saucer's attacks can't reach you. None of them penetrate walls (not even the killer death beam!). The two best pieces of equipment are summoner weapons, or anything that penetrates walls (such as Solar Eruption[The solar chain knife thing]).Then enjoy farming all those rare drops from the Saucer!