In search of life in our solar system, Mars steals the spotlight (thanks, David Bowie). In recent years, Jupiter's fourth largest moon, Europe, has become a promising alien kindergarten. Planet scientists have long suspected that Europe under its thick, icy crust harbors a huge ocean of liquid water. If the ocean of Europe also has an energy source – think of hydrothermal vents – and a few selected chemical elements, there is a good chance that it will support basic life forms.
This theory is based on many assumptions, but received on Monday one of the largest increases so far. An international team of astronomers announced that for the first time they directly detected water vapor in the European atmosphere. As detailed in an article published in Nature Astronomy this detection method is strong evidence that liquid water is present beneath the surface of Europe.
Ocean, "says NASA planetary scientist Lucas Paganini. "But it seems that this discovery is related to liquid water below the surface."
Much of Europe's knowledge was gained from data collected by the Galileo spacecraft on their Jupiter tour in the late 1
Scientists have been studying Jupiter's satellites with telescopes to gather more data – no small thing Europe is smaller than Earth's Moon and about 500 million miles away. In 2016, scientists used the Hubble Space Telescope to discover water lanes that appear to emerge from the surface of Europe. The springs were sporadic and Hubble spotted only a few of them. They were a hint, though.
A team of scientists led by Paganini Keck, the second largest telescope in the world, used 17 nights in late 2016 to study the atmosphere of Europe. If they discovered water vapor, they would have to deal with two leading theories to find out how it works. The first theory is that either a subterranean global ocean or liquid water in the crust of Europe hurled it into the atmosphere. The other is that charged particles from Jupiter bombard the moon and turn the water ice on the surface into water vapor.
In the latter case, Paganini and his team would expect about the same amount of water vapor throughout the European atmosphere. This reflects a constant bombardment of charged particles. However, during their two-and-a-half-week observation, they only discovered water vapor once, and there were a lot of of it. The steam entering the European atmosphere would have filled an Olympic swimming pool in a few minutes.
Having only seen the steam once, the scientists were confident that this water came from a cloud. Where there are springs, there is a good chance that there will be liquid water.
The next step, says Paganini, is to determine what springs produce and whether they display large amounts of liquid water on Europe. A cloud can be created by the outgassing of liquid water deep below the surface of Europe or by friction caused by ice slides or impacts. But to solve the puzzle, we have to send some robots to convince ourselves. "If we want to know more about this world of the ocean, we really need to get closer," says Paganini.
NASA is working on it. The Europa Clipper mission, which is expected to launch in 2025, is the first trip to the Galilean moon. Clipper, the largest spacecraft ever to be built, will be outfitted with a range of radiation-hardened instruments designed to look under the icy cover of Europe. If Clipper finds evidence of life, it could definitively justify a Europe lander – Arthur C. Clarke is damned.
Other Great WIRED Stories