In this talk I will attempt to give a perspective on the physics opportunities of oxygen-oxygen and proton-oxygen collisions in the LHC Run 3. The cosmic-ray community argues for a short pO run during Run 3, because this is the unique time-window for LHCf to take data. In the heavy-ion community, the origin of collectivity in small collision systems remains a central question that begs a timely answer. In the talk I will briefly present the constraints from the accelerator. I will then highlight the opportunities on what we can learn about a hydrodynamic quark-gluon plasma (QGP) and about hard probes propagating through such a QGP. I will end with a brief summary on cosmic ray opportunities.
Much of the talk will be based on the workshop OppOrtunities at the LHC (cern.ch/ooatlhc), as summarised in 2103.01939