\documentclass{beamer}
\begin{document}
\begin{frame}
\begin{columns}
\column{.5\textwidth}
Some text for the first column and a test footnote\footnotemark
\column{.5\textwidth}
Some text for the second column and a test footnote\footnotemark
\end{columns}
\footnotetext[1]{A test footnote in the first column}
\footnotetext[2]{A test footnote in the second column}
\end{frame}
\end{document}