The most common cause of aortic stenosis in patients 65 years of age and over is called senile calcific aortic stenosis.. With aging, protein collagen of the valve leaflets is destroyed, and calcium is deposited on the leaflets.ver time, excessive wear and tear leads to calcification, scarring, and reduced mobility of the valve leaflets. About 10% of bicuspid valves become significantly narrowed, resulting in the symptoms and heart problems of aortic stenosis.
A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind upon the nucleus of the comet.iagram of a comet showing the dust trail, the dust tail (or antitail) and the ion gas tail, which is formed by the solar wind flow. Gas and snow jets on Comet Hartley 2. In the outer Solar System, comets remain frozen and inactive and are extremely difficult or impossible to detect from Earth due to their small size.
Astronomers think comets are leftovers from the gas, dust, ice and rocks that initially formed the solar system about 4.6 billion years ago. Some researchers think comets might have originally brought some of the water and organic molecules to Earth that now make up life here.