Configuring two blogs on the same website?

Hello: I’m a new to WP, and engaged in the process of designing a new website for a group engaged in an academic research project. Our site has two purposes: first, to draw attention to the project and invite the participation of interested parties and institutions, and second, to provide a secure means of communication among those already affiliated with the project and its activities. We would like to invite the ‘uninitiated’ to engage with those involved with the project, but still want to facilitate ‘private’ communications among the participants through the website. I’ve already investigated a number of the available site management plug-ins, but am wondering whether I can configure the site to accommodate both a ‘private’ and a ‘public’ blog, with interfaces from separate web pages and (perhaps) even separate archive files, etc. Is this possible, or is it simply a matter of issuing specific access permissions to users and managing it all via the category system? Any guidance from designers or site administrators familiar with this issue would be most appreciated! Thank you!