The crew lands on a planet, looking for crystals of the mineral Ringwoodite. This mineral can exist only very deep inside the earth, much further than the depth of an average cave. However since they are on a rogue planet and not Earth, it may exist in shallower caves.
While "mining" in the cave August and Oliver are using rock hammers and chisels that are obviously toys.
Zayn clearly sports a 5 o'clock shadow.