Final answer:
The mass of the rover Sojourner remains the same as it travels from Earth to the surface of Mars. However, its weight changes due to the difference in gravitational field strength between the two planets.
Step-by-step explanation:
The rover Sojourner's mass would remain the same as it traveled from Earth to the surface of Mars. Mass is a measure of the amount of matter an object contains and it does not change with location. However, the weight of the rover would change. Weight is the force exerted on an object due to gravity and it depends on the mass of the object and the gravitational field strength of the planet.
On Earth, the rover would weigh more because the gravitational field strength is greater compared to Mars. As a result, the rover would experience a stronger gravitational force and hence a greater weight. On Mars, the rover would weigh less due to the weaker gravitational field strength.
For example, if the rover had a mass of 10 kilograms, on Earth its weight would be approximately 98 newtons (9.8 newtons/kg * 10 kg) while on Mars its weight would be approximately 37 newtons (3.7 newtons/kg * 10 kg).