A NASA space probe fell into a hibernation-like mode last week leaving scientists wondering why, NBC News reports.
Mission operations engineers discovered that the Kepler spacecraft went into emergency mode on Thursday, according the missions manager Charlie Sobeck.
Figuring out what happened will be difficult because Kepler is about 75 million miles from Earth.
Kepler found the most Earth-like planet ever spotted — 1,400 light years from Earth. The probe has discovered more than 1,000 confirmed exoplanets and finished its original mission in 2012. Because of its success, it has been kept on duty studying astronomical objects.