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.
Only around 180 impact craters have ever been discovered on Earth and around 30 per cent of them contain important natural resources of minerals or oil and gas. The largest and oldest known crater prior to this study, the 300 kilometre wide Vredefort crater in South Africa, is 2 billion years in age and heavily eroded.
The Vredefort crater was formed over 2 billion years ago, 60 miles from Johannesburg, South Africa. The diameter of the crater is believed to have been approximately 185 miles across but has since greatly eroded. It is the oldest and largest impact crater ever formed on Earth. In 2005, the crater became an UNESCO World Heritage Site because of its geological significance. (nasa)