两张不同幻灯片上的图表标题存在问题

Question

我在图片标题方面遇到了问题。目前，我的标题出现在两张幻灯片的底部。但是，我希望标题出现在不同幻灯片的图片下方。请帮忙，下面是我的代码。

    \begin{frame}
        \frametitle{Titan}
        \begin{columns}

        \column{0.5\textwidth}
        \centering

        \begin{figure}
            \includegraphics<1>[height=4cm]{PIA14445.jpg}
            \caption<1>{(Courtesy NASA/JPL-Caltech.)}

            \includegraphics<2>[height=4cm]{outgassing.pdf}
            \caption<2>{(Tobie et al., 2006)}

        \end{figure}

        \column{0.5\textwidth}
        \begin{block}{Features/Missions}
            \begin{itemize}
            \item Largest Moon of Saturn
            \item Cassini-Huygens mission
            \item Presence of Subsurface Ocean + Crust Made of Ice I
            \item Atmosphere (Nitrogen/Methane)
            \begin{enumerate}
                \item Methane needs to be replenished from the interior
            \end{enumerate}
            \end{itemize}

        \end{block}

        \end{columns}

    \end{frame}

Answer 1

\documentclass{beamer}
\begin{document}
 \begin{frame}[t]
        \frametitle{Titan}
        \begin{columns}[t]
        \begin{column}{0.49\textwidth}
        \centering

        \only<1>{\begin{figure}
            \includegraphics[height=4cm]{example-image-a}
            \caption{(Courtesy NASA/JPL-Caltech.)}
        \end{figure}}%
        \only<2>{\begin{figure} 
            \includegraphics[height=4cm]{example-image-b}
            \caption{(Tobie et al., 2006)}
        \end{figure}}
        \end{column}%
        \begin{column}{0.49\textwidth}
        \begin{block}{Features/Missions}
            \begin{itemize}
            \item Largest Moon of Saturn
            \item Cassini-Huygens mission
            \item Presence of Subsurface Ocean + Crust Made of Ice I
            \item Atmosphere (Nitrogen/Methane)
            \begin{enumerate}
                \item Methane needs to be replenished from the interior
            \end{enumerate}
            \end{itemize}

        \end{block}
        \end{column}%
        \end{columns}

    \end{frame}
\end{document}