Guide and timetable to this week's exciting events as New Horizons spacecraft encounters Pluto! Countdown on NASA TV begins 7:30 EDT (11:30 UTC) Tuesday.
Moon might harbor bits blasted off Earth billions of years ago. These lunar time capsules could hold secrets of what Earth was like as life first emerged.
If we took Earth and Venus - and had them orbit a cool, red star not too far away - could the James Webb Space Telescope tell which planet was habitable?