More evidence that Europa’s ocean is similar to Earth’s

Artist's illustration of how water from Europa's underground ocean can reach the surface. Credit: NASA / JPL-Caltech
Artist’s illustration of how water from Europa’s underground ocean can reach the surface.
Credit: NASA / JPL-Caltech

As one of the few places in the solar system other than Earth known to have an ocean, Europa has become one of the most fascinating worlds that we know of. This moon of Jupiter is small, but enticing – beneath its frozen surface of ice is a global ocean of water, making it a primary focus of study, especially in terms of the search for life elsewhere.

While this ocean’s existence is now accepted by scientists, its nature and composition have been a subject of long-standing debate. Is it similar to Earth’s oceans or different? New evidence now indicates that it is indeed quite similar to the oceans on our planet, it was announced today. Moreover, it can sometimes actually penetrate the outer icy shell and reach Europa’s surface.

The new findings, from studies led by astronomer Mike Brown at the California Institute of Technology (Caltech) and Kevin Hand from the Jet Propulsion Laboratory and published in the Astronomical Journal, show that chemicals from the water below can make their way to the surface, and vice-versa.

According to Brown, “We now have evidence that Europa’s ocean is not isolated – that the ocean and the surface talk to each other and exchange chemicals. That means that energy might be going into the ocean, which is important in terms of the possibilities for life there. It also means that if you’d like to know what’s in the ocean, you can just go to the surface and scrape some off.”

Using data from Keck II telescope in Hawaii, astronomers identified a type of magnesium sulfate salt, called epsomite, on Europa’s surface. As Brown explains, “Magnesium should not be on the surface of Europa unless it’s coming from the ocean. So that means ocean water gets onto the surface, and stuff on the surface presumably gets into the ocean water.”

The trailing hemisphere of Europa has long been known to have reddish coloured blotches and streaks, the origin of which has been unknown. The volcanoes on the nearby but larger moon Io spew out sulfur, some of which lands on Europa’s trailing side. Is that just a coincidence?

“We now have the best spectrum of this thing in the world,” Brown said. “Nobody knew there was this little dip in the spectrum because no one had the resolution to zoom in on it before.”

There’s a twist now though. Before, it was thought that the magnesium sulfate originated from the ocean, but now it seems to be a product of the sulfur from Io combining with another magnesium-bearing mineral on the surface – magnesium chloride, which does come from the ocean. This also means that the ocean is most likely chlorine-rich rather than sulfate-rich. In other words, it is salty in a manner similar to Earth’s oceans. As Brown states, “If you could go swim down in the ocean of Europa and taste it, it would just taste like normal old salt.”

Does this increase the chances for there being some kind of life in this hidden ocean? As Hand puts it, “If we’ve learned anything about life on Earth, it’s that where there’s liquid water, there’s generally life. And of course our ocean is a nice salty ocean. Perhaps Europa’s salty ocean is also a wonderful place for life.”

There is also a longer, more detailed article by Brown here (in three parts).

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