The Palace of Versailles, the Grand and the Petit Trianon are closed. 
You may choose a ticket online.  

The park of Versailles, the lake of the Swiss Guard and the Estate of Marly are open to walking from 8 a.m. to 6 p.m. 
Access to the Park is possible by the Queen's gate, the Saint Anthony gate and the Sailors gate
Conditions to access the estate of Versailles.