Asteroid
Whilst most asteroids are contained within a main belt that exists between the orbits of Mars and Jupiter there are many inside Earth's orbit, some cross Earth's path and a few have hit Earth in times past. It is likely these asteroids are the material left over from the early solar system - those that didn't coelesce into a rocky planets. The largest asteroid in our solar system is 1 Ceres. At 974 km in diameter, it is huge and contains about 25% of the mass of all the asteroids combined. The gravity on Ceres is about 1/36th Earth's, and by my calculations is still way too high to jump off into orbit!