Life on Jupiter's moon Europa? NASA launches mission to discover clues

Life on Jupiter's moon Europa? NASA launches mission to discover clues

A SpaceX rocket lifted off from Cape Canaveral in Florida today, carrying NASA's $5 billion dream to find evidence of life on a distant moon. This mission — the most ambitious search for life beyond Earth since NASA began exploring Mars decades ago — will now travel toward Jupiter to study a vast ocean hidden beneath the icy crust of its moon Europa.

In the coming weeks, the Europa Clipper probe will perform crucial maneuvers in space, such as deploying radar antennas in preparation for studying the moon. “We're watching with excitement,” says Kathleen Craft, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “Everything has to go well.”

If everything works, the spacecraft will reach Jupiter in 2030 and make numerous flybys of Europa. It will attempt to answer some of the most profound questions in astrobiology — including whether Europa's ocean contains chemical nutrients and other energy sources that can support life 1.

The mission scientists emphasize that the Clipper, named after the merchant ships of the 19th century, is not searching for life; rather, their goal is to determine whether Europe has the ingredients for life. If the mission shows that Europa is habitable, this discovery would dramatically expand the chances of finding life on icy worlds in other solar systems. “Studying Europa teaches us not to limit ourselves,” says Lynnae Quick Henderson, a planetary scientist at NASA Goddard Space Flight Center in Greenbelt, Maryland.

Terrain of “Chaos”

Europa, one of Jupiter's largest moons, was not considered a promising place to look for life for centuries. But in the mid-1990s, NASA's Galileo mission flew close to the moon and discovered geological wonders. She saw "chaos" terrain that looked like fields of icebergs that had frozen, and enormous bumps on the surface that appeared to be covered in reddish material. Galileo also measured a strange chatter beneath Europa's surface — evidence of a buried salty ocean 2.

The scientists want Clipper to confirm this discovery and find out more about the hidden body of water. “We will be able to describe what this habitable environment looks like,” says Ingrid Daubar, a planetary scientist at Brown University in Providence, Rhode Island, who works on Clipper for NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

The Ocean of Europa, thought to contain more than twice the volume of all of Earth's oceans, formed billions of years ago thanks to Jupiter's gravity. This force generates enough frictional heat to keep the ocean liquid, although temperatures on the moon's surface never rise above about -140 °C. The icy shell over the ocean is estimated to be at least 20 kilometers thick 3, and the water below is probably 60-150 kilometers deep (see “Deep Dive”). Clipper will confirm the thickness of both layers and help shed light on ocean dynamics, says Elizabeth Spiers, a planetary oceanographer at the Woods Hole Oceanographic Institution in Massachusetts.

The ingredients for life

On Earth, volcanic rocks on the seafloor can interact with ocean water to create chemical reactions that generate energy and allow microbes, worms, and other creatures to thrive. Similar deep-sea springs could also exist on Europa.

Another way life could be supported on Europa is through the energy the moon receives from Jupiter's powerful radiation. The planet bombards Europa with charged particles powerful enough to break chemical bonds in the moon's icy crust and produce small molecules such as hydrogen and oxygen 4.

And then there are the icy outcroppings coated with reddish material that could be salts and sulfate compounds from Europa's subsurface. “If this comes from the ocean, it will be an exciting place to look for signs of habitability,” says Cynthia Phillips, a planetary geologist at JPL. Clipper's instruments (see "Moonmapper") will study the material to learn more about the composition of the hidden ocean.

Finally, Clipper will also look for geysers, or flakes, that eject liquid into space through cracks in Europa's ice shell. Saturn's moon Enceladus has many such flakes, which contain hydrogen, carbon, silica grains and other life-friendly ingredients. Researcher have discovered evidence of similar flakes on Europa; if Clipper sees one, it could fly through the spray and analyze its contents.

Challenges in sight

In the more than four years that Clipper will study Europa, it will fly over the moon 49 times and come within 25 kilometers of the surface 5. Their cameras will photograph Europe in five times more detail than Galileo's cameras.

But there are many technical challenges ahead for the mission. One of these is survival in Jupiter's strong radiation belts; NASA plans for Clipper to avoid these as much as possible by traveling in an elliptical orbit. The threat from the belts caused panic in May when NASA engineers learned that more than 1,000 electronic transistors already installed in Clipper could fail under high levels of radiation. This discovery sparked a months-long investigation; NASA now says it is confident the transistors will be fine.

Clipper will explore Europe around the same time that the European Space Agency's JUICE spacecraft surveys the region, particularly Jupiter's two other moons, Ganymede and Callisto. (Jupiter has 95 moons.) "Between the two [missions] we will understand the whole system much better," says Ines Belgacem, a planetary scientist at the European Center for Astronomy in Madrid.

At the end of Clipper's mission, the plan is to crash them onto Ganymede, which also has a buried ocean but with a much thicker ice cover than Europa, theoretically protecting that moon's waters from contamination. This makes the journey an exploration of Europe's "vast and enticing seas", as described by the US poet Ada Limón, end abruptly.

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