the following answer originates from my knowledge or is an edit of an other users knowledge. i have underlined words were not hyperlinks and have been done so for the public's better understanding.
In our solar system Mercury is the smallest of the eight planets, and is the only one not to have an atmosphere. This may be due to:-
A planet's atmosphere doesn't have strength.
Jupiter and all the gas giants.
Not all planets have wind. Wind is caused by the movement of gases in an atmosphere, so planets without a significant atmosphere, like Mercury or the Moon, would not have wind. Additionally, the intensity and frequency of wind can vary greatly depending on factors such as atmospheric composition, temperature gradients, and surface features.
Negative, not only do the inner planets have atmospheres, but the outer planets also have atmospheres. The masses of the outer planets are great, enough easily to hold an atmosphere. In fact it's Mercury, an inner planet, that has almost no atmosphere. True, Mercury has a less mass and the closeness to the sun make it impossible to hold on a atmosphere. As matter in fact, Mars had a atmosphere, but the solar wind had almost eaten all the atmosphere that Mars had.
Some dwarf planets, like Pluto, have thin atmospheres composed mainly of nitrogen, methane, and carbon monoxide. However, the atmospheres of dwarf planets are not as substantial as those of larger planets like Earth or Jupiter.
air and gasses and for some no atmosphere
they all have different gasses in there atmosphere
Atmosphere.
A planet's atmosphere doesn't have strength.
No many like Mars have no atmosphere at all.
Yes, all planets have atmosphere but to my knowledge mars' is not breathable.
The thinnest atmosphere belongs to planet Mercury . . . it may have no atmosphere, at all.
because its cold
Gas particles (atoms, molecules) composing the atmosphere of a planet have a mass, therefore they are trapped by the gravitational field of the planet. This is not only true for giant planets but applies to all planets with atmosphere.
Jupiter and all the gas giants.
The outer planets does not have enough oxygen to sustain life, or they don't have an atmosphere at all.
The inner planets Mercury, Venus, Earth, Mars are are all relatively small, they are all rocky, they all have a relatively thin atmosphere.