The US space agency says the new findings come from both the agency’s Cassini spacecraft and the Hubble Space Telescope.
'These new discoveries will help inform future ocean world exploration - including NASA’s upcoming Europa Clipper mission planned for launch in the 2020s - and the broader search for life beyond Earth,' NASA said.
It will reveal the finding at 2pm on Thursday - but refused to give any more clues.
The event, to be held at the James Webb Auditorium at NASA Headquarters in Washington, will include remote participation from experts across the country.
The include several members of the Cassini team, raising speculation the announcement could be a revelation about Jupiter's sixth-closest moon Europa, ahead of the 2020 Europa Clipper mission, or Enceladus, the sixth-largest moon of Saturn.
Jupiter's sixth-closest moon Europa is one of the most interesting bodies in our solar system when it comes to the hunt for alien life.
The moon, which lies 500 million miles from the sun, has an ocean lying beneath its surface which makes it one of the most likely places in the solar system for life to thrive.
Because Europa has the potential to have more liquid water than we have on Earth, some have speculated that the surprise reveal could be evidence for life.
The 1,900-mile-wide (3,100 km) moon harbors a huge ocean of liquid water beneath its icy shell.
Astronomers think this ocean is in contact with Europa's rocky mantle, making all sorts of interesting chemical reactions a possibility.
Instead of direct evidence of life, however, experts have said it is more likely to be a step towards finding it.
The announcement could be related to faint plumes of water spotted on the moon back in 2012.
Hubble used a spectrograph to see normally invisible plumes of water vapour, shown in pictures as blue pixels above the moon.
'By far the simplest explanation for this water vapour is that it erupted from plumes on the surface of Europa,' lead author Lorenz Roth of Southwest Research Institute in San Antonio said at the time.
'If those plumes are connected with the subsurface water ocean we are confident exists under Europa's crust, then this means that future investigations can directly investigate the chemical makeup of Europa's potentially habitable environment without drilling through layers of ice.
'And that is tremendously exciting.'
Bill McKinnon, a planetary scientist at Washington University in St. Louis, told Business Insider the announcement is likely to be connected to these plumes.
'A plume confirmation would be a great thing,' McKinnon added, but 'I have no insider knowledge.
Hubble's instruments were not designed to see any of Europa's geology or study what elements are present in the plumes, so an announcement of this kind is unlikely.
According to dailymail.co.uk