PHYSICS SIA - NEWS BITE
Did you know that atmosphere can be lost through many ways? Perhaps this would clear the question in your head why we can see the surface of Mercury or Mars so easily, but not Venus.
In thermal escape, air particles high up in the atmosphere gain energy from the sun, reach escape velocity and fly out. Non-thermal escape would mean asteroid hits or passing solar winds that could drag or push the atmosphere into space. Solar radiation can ionize molecules. When ions collide or recombine; the energy released can split the molecules into atoms and throw them out.
Mars lost nearly 90% of its atmosphere by solar wind, but it’s better for Earth. It is still possible that Earth will look like Venus in a few billions years’ time. Life will die out due to loss of atmosphere, so we must take care of our atmosphere from now, and stopping ozone depletion is the first step to that. 
asteroid hit
air expanding out and rising due to heat form the sun.
air evaporating off molecule by molecule
