What can I learn at open-house events for PhD programs that would be difficult to learn through other channels prior to accepting an offer? [duplicate]

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• What are the 'right questions' to ask professors at a visit day for prospective graduate students? 2 answers

I have received a few offers for PhD programs in the US that I am interested in, and several of these have open-house events coming up in the next few weeks. I have been in contact with potential advisors at several of these programs, but have had very limited or no contact with current graduate students there. My current information on these programs comes from offer letters, interactions with professors (both my undergraduate advisor, and professors at institutions hosting these open-houses), and departmental websites.

My primary goals with these events are:

1. 
   

   Meet with potential advisors, and determine who I could work well with, and

   
   


2. 
   

   Talk to current PhD students; see if I can learn anything about departmental politics, the funding situation, and anything else that the department doesn't advertise to prospective students.

   
   

Which questions should I be sure to ask, and to whom? What opportunities do I have at open-houses that I will never have again before I need to accept an offer?

If it matters, the programs I am considering are in physics, geophysics and Earth sciences departments, depending on which department the space sciences faculty happen to be in.