A heart-shaped feature was viewed on Pluto’s surface in the most detailed photo yet returned by NASA’s New Horizons probe, which has now begun its final run of its historic flyby of the planet. After a voyage of nine years, New Horizons is almost 4.8 billion km away, where radio signals, even travelling at the speed of light, need 4.5 hours to reach Earth. Round-trip communication between the spacecraft and its operators requires about nine hours.