Niamh,
when we talk about “inquiry-based activities” in this course, we are specifically referencing the Framework for Inquiry that is outlined in this module.
So, your planet exploration can be based on a prompt – what is it like to live on another planet (would you make it just our solar system – or consider some of the vastly different types of worlds that have been discovered around other stars? – if you did, then the ExoPlanet posters could make a great prompt).
Children should then share what they currently understand and share their questions as they wonder and explore. Then they can structure a starter question, make a prediction based on science about that starter, then investigate to check if their science is a good model. The next step might be “what animals might live there” or some other ‘thoughtful action’.
If you do want to include art, you might look at adapting this resource (on how features of art are connected to science) https://www.jpl.nasa.gov/edu/teach/activity/art-the-cosmic-connection/