\begin{table}%t2
%\centering
\par
\caption {\label{tab:mass}Masses and numbers of objects in the Kuiper belt.    }
\begin{tabular}{rrr}
\hline\hline
\noalign{\smallskip}
		& Before debiasing	& After debiasing\\
\hline 
$M_{\rm CKB+RES}$ [$0.001~ M_\oplus$]	& $4.4$			& $52$\\
$M_{\rm SDO}$     [$0.001~ M_\oplus$]	& $2.2$			& $65$\\
$M_{\rm total}$   [$0.001 ~M_\oplus$]	& $6.6$			& $117$\\
$N_{\rm CKB+RES}\ (s>75~\km)$	& $1100$		&$39~700$\\
$N_{\rm SDO}\ (s>75~\km)$	& $160$			&$45~200$\\
$N_{\rm total}\ (s>75~\km)$	& $1260$		&$85~000$\\
\hline
\end{tabular}
\tablefoot {CKB is the classical Kuiper belt,
  RES are the resonant objects,
  and SDO denotes the scattered disk objects.}
\end{table}