  The study of planetary atmospheres is critical to our understanding of the
origin and evolution of the Solar System. The combined effect of various
physical and chemical processes over billions of years have resulted in a
variety of planetary atmospheres across the Solar System. This paper performs a
comparative study of planetary atmospheres and their engineering implications
for future entry and aerocapture missions. The thick Venusian atmosphere
results in high deceleration and heating rates and presents a demanding
environment for both atmospheric entry and aerocapture. The thin Martian
atmosphere allows low aerodynamic heating, but itself is not enough to
decelerate a lander to sufficiently low speeds for a soft landing. With their
enormous gravity wells, Jupiter and Saturn entry result in very high entry
speeds, deceleration, and heating making them the most demanding destinations
for atmospheric entry and impractical for aerocapture. Titan is a unique
destination, with its low gravity and greatly extended thick atmosphere
enabling low deceleration and heating loads for entry and aerocapture. Uranus
and Neptune also have large gravity wells, resulting in high entry speeds, high
deceleration and heating compared to the inner planets, but are still less
demanding than Jupiter or Saturn.
