Here's why:

* Mass vs. Weight: It's important to distinguish between mass and weight.

* Mass is the amount of matter in an object. It's a fundamental property and stays the same regardless of location.

* Weight is the force of gravity acting on an object's mass. It changes depending on the gravitational pull of the planet or moon.

* Earth's Mass is Greater: Earth has a much larger mass than Mars. Earth's mass is about 10 times greater than Mars's mass.

* Gravity's Role: While Mars has a weaker gravitational pull than Earth, this only affects the weight of an object on its surface. It doesn't change the actual mass of the planet.

In short: Earth is a much larger and heavier planet than Mars.