\begin{table}%t3
\caption{ Comparison between the calculated CO$_{2}$ half-times involved in the methylammonium methylcarbamate (C) thermal formation and the calculated residence times of CO$_{2}$ on water ice at different temperatures.\label{tbl-3}}
%\centerline
 {
\begin{tabular}{lll}
\hline
\hline
         Temperature & CO$_{2}$ half-times to& CO$_{2}$ residence times\\
          (K) &  C formation (yr)& on water ice$^{1}$ (yr)\\
\hline\\[-3.2mm]
50 &$8\times10^{-2}$ & $7\times10^{4}$ \\
60 &$2\times10^{-2}$ & $5\times10^{0}$\\
70 &$6\times10^{-3}$ & $6\times10^{-3}$\\
80 &$3\times10^{-3}$ & $4\times10^{-5}$\\
90 &$2\times10^{-3}$ & $7\times10^{-7}$\\
100 &$9\times10^{-4}$ & $3\times10^{-8}$\\
\hline
\end{tabular}}
\medskip
\par
Reference. (1) \citet{Sandford93}.
\end{table}