The segment of the atmosphere that blends into interplanetary space is called the exosphere.

Here's why:

* Exosphere: This is the outermost layer of the atmosphere. It's extremely thin and extends far out into space, eventually blending with the vacuum of interplanetary space. The exosphere is characterized by very low density, with atoms and molecules escaping into space.

* Other Layers: The atmosphere has other layers too, but they are closer to Earth:

* Troposphere: The layer where weather occurs.

* Stratosphere: Contains the ozone layer.

* Mesosphere: The coldest layer.

* Thermosphere: Where the International Space Station orbits.

Let me know if you have any other questions about Earth's atmosphere!