Artistic impression of Europe's interior, based on data obtained from Galileo spacecraft Credit: NASA  In 2012 Hubble took a picture of Europe, which shows what many interpreted as a vapor cloud emerging from a rift in the frozen surface emerged and shot up to 200 km. high. (By comparison, Mount Everest is only 8.8 km high.) In 2016, there were other indications of Hubble, which pointed to flags.
This composite image suggests that water vapor breaks out at the 7 o'clock position in front of the edge of Jupiter's moon. The feathers, photographed by Hubble's Imaging Spectrograph, were seen as silhouetted as the moon passed Jupiter. Thanks to Hubble's UV sensitivity, it has been able to identify the features that have risen more than 160 kilometers above the European ice surface. It is believed that the water comes from an underground ocean on Europe. Hubble data was recorded on January 26, 2014. The Europe image overlaying the Hubble data is compiled from data from the Galileo and Voyager missions. Image Source: NASA, ESA, W. Sparks (STScI) and the USGS Astrogeology Science Center
NASA's Galileo spacecraft detected disturbances in the magnetic field of Jupiter near Europe during the time of this spacecraft on Jupiter from 1995 to 2003 , Scientists attributed these disorders to a salty ocean that could exist beneath the frozen surface of the moon, as a salty ocean can channel electricity.
The Galileo spacecraft also approached the surface of Europe at a distance of 206 km (128 mi) in 1997, and some researchers suspect that it actually flew through a cloud.
However, with all this data, there was no definite discovery of water. That has now changed.
"This first direct identification of water vapor on Europe is a critical confirmation of our original discovery of atomic species …"
Lorenz Roth, astronomer and physicist, KTH Royal Institute of Technology in Stockholm, co-author.
A team of scientists led by Lucas Paganini, a NASA planetary scientist, has published an article announcing the discovery of water in Europe. The paper is titled "Measuring Steam in a Quiet Environment on Europe". It was published on 18 November in the journal Nature.
In a press release, Paganini said, "Basic chemical elements (carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur) and energy sources, two of three conditions for life, exist throughout the Solar System. But the third – liquid water – is hard to find beyond the earth. Although scientists have not yet directly detected liquid water, we have found the next best thing: water in vapor form. "
The image of this artist shows what steam clouds might look like emitted from the South Pole of Europe. Image: NASA, ESA, L. Roth (Southwest Research Institute, USA / University of Cologne) and M. Kornmesser.
Paganini and the other scientists said that in a few minutes they had discovered enough water to fill an Olympic swimming pool; about 2360 kg / second (5202 lbs / sec.) They also report that the water rarely appears. "The interesting thing about this work for me is not only the first direct detection of water over Europe, but also its absence as part of our detection method."
The results are from the observation of time with the W.M. Keck Observatory in Hawaii. During 17 observation nights in 2016 and 2017, the team only once found the faint, clear signal of water vapor. The steam was discovered on Europe's leading hemisphere as it orbited Jupiter. (Europe is tidal to Jupiter, just as the moon is to the earth.)
Water emits infrared light at certain frequencies when it interacts with solar radiation. Using a spectrograph at the Keck telescope, scientists have measured the chemical composition of Europe's leading hemisphere.
Water molecules emit certain frequencies of infrared light when they interact with solar radiation. Credits: Michael Lentz / NASA Goddard
This underscores the apparent thriftiness of large feathers on this icy world, "said Lorenz Roth, astronomer and physicist at Stockholm's Royal Institute of Technology, who led the Hubble 2013 study and co-author this recent investigation was.
Roth refers to the detection of components that make up water, above Europe. That's fascinating, but not synonymous with discovering water. To find the water, the team had to use the ground-based Keck Observatory and its spectrograph because no current spacecraft can detect water.
The twin Keck telescopes fire their laser-guided stars into the heart of the Milky Way on a beautifully clear night on the summit of Mauna Kea. Credit: keckobservatory.org/Ethan Tweedie
It is not easy to determine that it is water and not just the constituents of water, especially from Earth. The team behind this study had to deal with the water in the Earth's atmosphere, relying on complex mathematical models and computer models.
The team is confident in its results, even though it recognizes that a mission to Europe is needed to really understand the moon.
"We have conducted careful safety testing to remove potential contaminants in land-based observations," said Avi Mandell, a Goddard planetary scientist in Paganini's team. "But eventually we have to move closer to Europe to see what's really going on."
Hopefully, the scientists – and the rest of us – will not have to wait too long to get more definitive answers to Europe's many questions. The Europa Clipper was put into its final design phase in August 2019 and is expected to hit the market in the mid-2020s. It will contain a whole range of tools to discover the secrets of Europe. Most exciting is his ground-penetrating radar. It could peer through the ice and confirm once and for all the existence of an underground ocean.
As if an orbiter were not enough, it is also called a European lander.
Artistic representation of a possible Europa-Lander mission that would explore the surface of the icy moon in the coming decades. Credit :: NASA / JPL-Caltech
In 2019, NASA's Congress awarded $ 195 million to develop a lander as part of the Clipper mission. NASA has never asked for this money, probably because it is difficult to land on the surface of Europe. Maybe the Congress knows that landings attract a lot of public interest.
Of course, not only the surface environment of Europe is problematic. The radiation around Jupiter is extreme and to be successful the Europa Clipper has to follow broad elliptical orbits and approach Europe for some time before it can go to safety. So the NASA Juno spacecraft competes with Jupiter's radiation.
Nevertheless, the Clipper can image all feathers directly and even scan them with its mass spectrometers. It will also be able to study the surface in more detail than ever before.
But we have to be patient. It took Juno five years to reach Jupiter. When the Europa Clipper mission starts in the mid-2020s, we will not receive scientific results until 2030 or later.