NASA officials announced on Wednesday May 15 that its Kepler space observatory, launched to find extraterrestrial planets, is experiencing major difficulties.

The problem started with the observatory's "reaction wheels," which position the spacecraft. In January, friction started to be caused by one of the wheels. On Sunday Kepler put itself in safe mode due to the problem. Following commands, the wheel would not respond.

"We aren't ready to call the mission over," John Grunsfeld, associate administrator at NASA, said in a press conference. "We will look at this data very carefully to see if we can get back into a science mode."

The problem with the wheel could mean the end of Kepler's mission, given that one is already broken and three are required to position the observatory. Possible options at this juncture include reestablishing contact with the old wheel, now turned off, or fiddling with the recently malfunctioning one.

"This is indicative of an internal failure in the wheel," deputy project manager Charles Sobeck said. "It will take us a few weeks to put together a plan... to get a wheel turning again."

It's still possible that Kepler's thrusters could be used for movement, however that would result in less precise positioning. There may be some sort of other science that astronomers could perform with Kepler without such precision.

Kepler was launched in 2009 and is currently about 40 million miles from Earth. It has confirmed 115 planets so far and has compiled a list of 2,740 additional ones.

"The mission itself has been spectacularly successful. It has exceeded our science expectations," Sobeck said.

Recently Kepler discovered two new planetary systems with potentially habitable planets. NASA plans to launch its next exoplanet hunter TESS in 2017.