What on Earth is that rocket ship icon on your Facebook mobile app?

Some users have noticed a mini missile on either the top or bottom task bar of their News Feed, depending on whether they’re using Android (top) or iOS (bottom), quietly appearing over the past month.

Turns out, this rocket rocking social media is an experimental, alternative News Feed that Facebook is soft-launching in some markets, with puzzled users tweeting about it from California to Croatia. It features popular posts, articles, photos and videos from Facebook Pages and news media organizations that you haven’t liked or followed, but that it thinks you might be interested in based on what you currently “like” or follow. It’s similar to Instagram’s Explore tab, which also curates posts that the company’s algorithm has calculated that would be appealing to you.

All that Facebook would tell Moneyish is that, “We are testing a complementary feed of popular articles, videos, and photos, customized for each person based on content that might be interesting to them. We’ve heard from people that they want an easy way to explore new content they haven’t connected with yet.”

But not every user is on board.