While opening Mathematica 9, it says:
/usr/local/Wolfram/Mathematica/9.0/SystemFiles/FrontEnd/Binaries/Linux-x86-64/Mathematica: /usr/local/Wolfram/Mathematica/9.0/SystemFiles/Libraries/Linux-x86-64/libz.so.1: version `ZLIB_1.2.9' not found (required by /usr/lib/x86_64-linux-gnu/libpng16.so.16)