The inner planets are much smaller than the outer planets and because of this have relatively low gravity and were not able to attract large amounts of gas to their atmospheres. Four of these planets Mercury Venus Earth and Mars are called the inner planets. Solar System Inner Planets Powerpoint Presentation Solar System Middle School Science Resources Earth And Space Science Earth the third planet from the Sun is the only planet with large amounts of liquid water and the only planet known to support life. . The inner planets which are arranged from the smallest to largest includes the Mercury Mars Venus and Earth. Saturn is the second largest planet in our Solar System. Mercury mars venus and earth. Mercury is the innermost planet and is also the smallest planet of our solar system. Is Earth the largest inner planet. The inner planets are composed of silicates and metals. Jupiters radius is about 110 the ...