A planetary probe is a spacecraft carrying instruments intended to explore the physical properties of outer space or celestial bodies other than Earth. Consider a planetary probe travelling inward towards the center of a planet. At 600 m above the surface of the planet, the electric eld generated by the planet is directed up and has the magnitude of 180 N/C. At 500 m above the surface, the direction of the electric eld remains the same, but the magnitude is 125 N/C. Identify the nature of the source charge and magnitude of the charge density in the region described above.

A planetary probe is a spacecraft carrying instruments intended to explore the physical properties of outer space or celestial bodies other than Earth. Consider a planetary probe travelling inward towards the center of a planet. At 600 m above the surface of the planet, the electric eld generated by the planet is directed up and has the magnitude of 180 N/C. At 500 m above the surface, the direction of the electric eld remains the same, but the magnitude is 125 N/C. Identify the nature of the source charge and magnitude of the charge density in the region described above.