An artist's concept shows the New Horizons spacecraft as it approaches Pluto and its largest moon, Charon, in July 2015. Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute hide caption

itoggle caption Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Artist concept of New Horizons spacecraft. The Hubble Space Telescope is being pressed into service to help scientists look for a post-Pluto target for the space probe. Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute hide caption

itoggle caption Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute