The space agency has responded to speculation about its announcement next week with a major spoiler alert
Imaginations ran wild when the American space agency said the Hubble Space Telescope had captured "surprising evidence of activity" on the moon, which would be revealed in a teleconference at 7pm UK time on Monday.
The moon has a global ocean beneath its icy crust that many experts believe could harbour life.
Nasa's "teaser" announcement sparked a frenzy of excitement in the Twittersphere with space enthusiasts trying to guess what might have been found.
Many picked up on the excitement and speculated that we were about to hear about an alien discovery.
Unfortunately the space agency posted a tweet of its own that poured cold water on notions of watery aliens on Europa. It read: "Monday, we'll announce new findings from Jupiter's moon Europa. Spoiler alert: NOT aliens."
If the plumes are shown to be linked to the moon's sub-surface ocean, it would make the job of investigating the habitable potential of Europa much easier. Instead of having to drill through the moon's thick, icy shell, scientists could analyse the chemical content of the plumes.
The 1,900-mile-wide moon is thought to hold two to three times as much water as all the Earth's oceans.
Europa's ocean is believed to be salty, and warmed by powerful tidal forces generated by Jupiter's gravity so that it remains unfrozen.
Some experts believe it could be the best place in the Solar System to find evidence of extra-terrestrial life.