Rocks within the asthenosphere are not in a solid state. Instead, they are in a partially molten state, known as solidus.

Here's why:

* The asthenosphere is a layer of the Earth's mantle located beneath the lithosphere.

* It's characterized by high temperatures and pressures.

* These conditions cause the rocks to behave in a semi-solid, ductile manner. This means they can flow very slowly over long periods, much like a very viscous fluid.

* The rocks in the asthenosphere are not fully melted, but they contain a significant amount of molten material. This molten material allows for the movement of tectonic plates, which are part of the lithosphere, which sits on top of the asthenosphere.

So, while rocks in the asthenosphere are technically solid, their behavior is more akin to a viscous fluid due to the partial melting.