Is it possible to deploy SSIS 2012 package on SQL Server 2008

no, you cant. SSIS package are not backwards compatible.

Also it doesn't make much sense if you think about it. If it was the other way around, "maybe" it could be done because 2012 would somehow be aware of 2008 structure, but 2008 engine isn't aware of 2012 package structure.

You cannot run it with the 2008 version of dtexec and you certainly cannot deploy it into the catalog, but if you could install the minimum you need to run SSIS 2012 onto a server somewhere you could then execute the package from filesystem with the 2012 version of dtexec.

See also http://msdn.microsoft.com/en-us/library/bb522577.aspx