How can I improve morale among my fellow colleagues?

I am working in a big financial advisory firm. Next project is quite big and they made up a team of no less than 6–8 people. The main problem is not the difficult project itself, is that everybody seems not motivated, sad and the atmosphere in our dedicated office @client building is really heavy.
What can I do/say to make things better?(I am an analyst, that means I have 2 year experience. Team is made up of people with more experience and two new hired).