How do you unlock the "Tycho Magnetic Anomaly" achievement in Iron Marines?

Help the space monkeys get the secrets of the Monolith in Mission 4.

Tycho Magnetic Anomaly

The space monkeys are located to the right of the Etherium deposit north of your original Refinery. Just head straight up then to the right at the start of the mission and you'll see 4 of them hanging around on the cliffs. Simply tap the 4 monkeys to unlock the "Tycho Magnetic Anomaly" achievement.