Continuous positive airway pressure (CPAP) machines are used to maintain an open airway in patients diagnosed with obstructive sleep apnea. The machine functions by blowing pressurized air into the airway via mask at a setting determined by sleep study and prescribed by a physician.
Also the second largest impact structure on Earth, the 1.85 billion years old Sudbury crater in Canada, hosts world-class mineral deposits - in this case nickel-rich minerals that were melted and concentrated by the extreme heating caused by the impact.
The largest craters on the Moon, like Mare Imbrium which is over 1100 km in diameter, have been flooded by lava and we can only see parts of their circular outline. Because these dark mare (which means 'sea') have few craters on them, they must be younger that the surrounding areas. Simple craters like Moltke (which is 6.5 km in diameter and 1.3 km deep), have a smooth bowl-like shape with smooth walls. Most small craters less than about 15 km in diameter are simple craters.