What inner planet's atmosphere has low air pressure and it's mostly carbon dioxide?
Venus has a dense atmosphere that consists primarily of carbon dioxide. The pressure of the atmosphere on Venus's surface is 90 times that of Earth's atmosphere.
Earth is the terrestrial planet that has oxygen in its atmosphere. Some other elements in the atmosphere are nitrogen and carbon dioxide. Mercury, Venus, and Mars are the other terrestrial planets, but their atmospheres are composed of other elements. For example, Venus' atmosphere is composed primarily of carbon dioxide.
Mercury has no real atmosphere, so it's a bit like the moon in that respect. Venus has a very thick atmosphere of mainly carbon dioxide, it has a huge surface pressure of around 93 bar, around 93 time that of earths. Earths atmosphere is mainly nitrogen (79%) and oxygen (20%) with some carbon dioxide (1%) roughly speaking. Mars has a thin atmosphere, mainly carbon dioxide.
What planet has a greenhouse effect that warms the planet due to the trapping of infrared radiation by carbon dioxide in the planet's atmosphere?
No. The moon with most atmosphere is Callisto which has an extremely thin atmosphere with an atmospheric pressure of 7.5 bar which is made of Carbon Dioxide and Oxygen. Io has a trace of an atmosphere made of Sulfur Dioxide, while Ganymede has a trace of an atmosphere made of Oxygen. Compare these with Saturn's moon Titan which has a dense atmosphere.