  We give a new formula for all tree-level correlators of boundary field
insertions in gauged N=8 supergravity in AdS_4; this is an analog of the
tree-level S-matrix in anti-de Sitter space. The formula is written in terms of
rational maps from the Riemann sphere to twistor space, with no reference to
bulk perturbation theory. It is polynomial in the cosmological constant, and
equal to the classical scattering amplitudes of supergravity in the flat space
limit. The formula is manifestly supersymmetric, independent of gauge choices
on twistor space, and equivalent to expressions computed via perturbation
theory at 3-point MHV-bar and n-point MHV. We also show that the formula
factorizes and obeys BCFW recursion in twistor space.
