Because the gravitational pull of the planet isn't strong enough to hold any gasses.
Mercury
Mars has almost no atmosphere. APEX=MERCURY has no atmosphere.
There aren't. Mercury has almost no atmosphere. Therefore, it cannot have storms.
The planet Mercury has almost no atmosphere, it's essentially a vacuum.
Mercury has only a trace atmopshere of hydrogen that is almost null.
Mercury is pitted with craters because Mercury has almost no atmosphere to protect itself.
Very, very little, as Mercury's atmosphere is almost a vacuum only minute traces of gasses are found.
Of the inner four terrestrial planets in our solar system - Mercury, Venus, Earth and Mars - Mercury has almost no atmosphere.
Mercury is so close to the Sun and so small that it has only a very small atmosphere. It has been blown away by the Sun's solar winds. That means that there is almost no air on Mercury.
The atmosphere on Mercury is about 42% oxygen, but is very thin as to be almost non-existent.
Mercury has almost no atmosphere so that could be the answer. The otherpossible answeris Mars, which certainly does have a (thin)atmosphere.
Mercury is so close to the Sun and so small that it has only a very small atmosphere. It has been blown away by the Sun's solar winds. That means that there is almost no air on Mercury.