Scientists detected a peculiar blob of heat-emitting material buried on the far side of the moon. The most likely culprit is a rock that is very rare outside of Earth.

Scientists have discovered an anomalous blob of heat on the far side of the moon.

This mysterious hotspot has a strange origin: It’s likely caused by the natural radiation emanating from a huge buried mass of granite, which is rarely found in large quantities outside of Earth, according to new research. On the moon, a dead volcano that hasn’t erupted for 3.5 billion years is likely the source of this unusual hunk of granite.