\begin{table}%t9
%%\centering

\par
\caption{\label{Mantle layering}Mantle layering.}
\begin{tabular}{llllll}
\hline \hline\noalign{\smallskip}
 & & Model 1 & Model 2 & Model 3 & Model 4\\
\hline
Maximum     & Layers              & 184               & 169               & 179               & 154               \\ 
Thickness   & Time (years)        & $4.38\times 10^6$ & $1.38\times 10^6$ & $4.28\times 10^5$ & $2.19\times 10^7$ \\ 
& Density (cm$^{-3}$)  & $5.95\times 10^6$ & $5.02\times 10^6$ & $3.39\times 10^6$ & $5.62\times 10^6$ \\ 
& Temperature (K)     & 18.1              & 17.1              & 15.0              & 17.8              \\
\hline
 & & Model 5 & Model 6  & Model 7   & Model 8  \\
\hline
Maximum     & Layers              & 121               & 169               & 126               & 119               \\ 
Thickness   & Time (years)        & $6.90\times 10^6$ & $2.14\times 10^6$ & $4.28\times 10^5$ & $2.14\times 10^6$ \\ 
            & Density (cm$^{-3}$) & $8.81\times 10^6$ & $3.20\times 10^6$ & $3.39\times 10^6$ & $3.20\times 10^6$ \\ 
            & Temperature (K)     & 20.7              & 14.7              & 15.0              & 14.7              \\
\hline
\end{tabular}
\end{table}