Here's why:

* Gravitational Potential Energy: Objects have potential energy due to their position within a gravitational field. The farther an object is from the source of gravity (like the Sun), the more potential energy it possesses.

* Conservation of Energy: As the asteroid moves away from the Sun, its kinetic energy (energy of motion) decreases. To conserve energy, this decrease in kinetic energy is converted into an increase in potential energy.

Think of it like a ball thrown upwards: as it rises, it slows down (loses kinetic energy) but gains potential energy due to its increasing height. The same principle applies to an asteroid moving away from the Sun.