On the Edge of Night and Day. Wren Chronicles, #2

A remote outpost. An alien life form. A mystery. Stella had her heart set on spending her work term as part of the second mission to the core of New Venus. Instead, she's assigned to a remote science outpost on a forgotten moon. To make things worse, she's stuck with Dizzy-her chaotic, endlessly curious classmate who talks too much, breaks too many rules, and seems determined to actually enjoy their exile. But as the days pass, Stella starts to see a different side of Dizzy as their work at the outpost reveals strange, breathtaking secrets.
A colossal fungal organism that might be sentient and is definitely growing. Mysterious, gravity defying particles. Fragments of research long buried. Then Dizzy stumbles across the biggest secret yet-a previous student died at the outpost under suspicious circumstances-circumstances that are happening again. Now, Stella and Dizzy must rely on each other to uncover the truth of what happened at the outpost-before whatever's growing out there comes for them next.