NASA Mission Will Look for Life

SCIENCE

NASA has taken the first small step in a mission to explore Jupiter’s icy moon Europa, one of the most likely places in our solar system for alien life to exist. (Smithsonian)

Our Emerging Explorer Kevin Hand has also been “Looking for Life” on Europa—learn how!

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit.

Illustration courtesy Jet Propulsion Laboratory

Discussion Ideas

The Smithsonian article says Europa is “one of one of the most likely places in our solar system for alien life to exist.” Why?
- First and foremost, “if anything is essential to life as we know it, it’s water, and Europa has bucketfuls.”
  - Read this blog post to learn more about why liquid water is almost certainly necessary for a planet (or moon) to be habitable.
  - Previous NASA missions (studying the Europan atmosphere and magnetic fields) have detected signs of an enormous liquid or ice ocean beneath Europa’s brittle outer crust. The Europan ocean is “anywhere from 6 miles to a few thousand feet below the ice, and it contains about two times as much water as all of Earth’s seas combined.”

Here are another two looks at the possible geology of Europa. Geologic features such as Europa’s lenticulae, or freckles, might be explained either by the existence of a warm, convecting ice layer, located several kilometers below a cold, brittle surface ice crust (top model), or by a layer of liquid water with a possible depth of more than 100 kilometers (bottom model). Illustration courtesy NASA/JPL — Here are two looks at the possible geology of Europa. Geologic features such as Europa’s lenticulae, or freckles, might be explained either by the existence of a warm, convecting ice layer, located several kilometers below a cold, brittle surface ice crust (top model), or by a layer of liquid water with a possible depth of more than 100 kilometers (bottom model).
Illustration courtesy NASA/JPL

This illustration shows the calculated volume of water on Europa, compared to Earth. Illustration by Kevin Hand (JPL/Caltech), Jack Cook (Woods Hole Oceanographic Institution), and Howard Perlman (USGS) — This illustration shows the calculated volume of water on Europa, compared to Earth.
Illustration by Kevin Hand (JPL/Caltech), Jack Cook (Woods Hole Oceanographic Institution), and Howard Perlman (USGS)

What is another reason Europa may be primed for life?
- It’s quite a dynamic little celestial body! Read our short-and-sweet media spotlight on Europa’s freckles to understand icy evidence of a warm interior.

Here are some more examples of Europa’s icy dynamism!

This conceptual illustration of the subduction process on Europa shows how a cold, brittle, outer portion of Europa's ice shell moved into the warmer shell interior. Illustration courtesy Noah Kroese, I.NK and the Jet Propulsion Laboratory — This conceptual illustration of the subduction process on Europa shows how a cold, brittle, outer portion of Europa’s ice shell moved into the warmer shell interior.
Illustration courtesy Noah Kroese, I.NK and the Jet Propulsion Laboratory

According to Smithsonian, “Like Earth’s shifting tectonic plates, Europa’s icy exterior also seems to be diving back into the liquid layer below in a process called subduction, possibly helping such material cycle through its seas.”

This is an artist's concept of a plume of water vapor thought to be ejected off the frigid, icy surface of Europa. Scientists calculate that the plume rises to an altitude of 125 miles (201 kilometers) and then it probably rains frost back onto the moon's surface. Illustration courtesy NASA/ESA/K. Retherford/SWRI — This is an artist’s concept of a plume of water vapor thought to be ejected off the frigid, icy surface of Europa. Scientists calculate that the plume rises to an altitude of 125 miles (201 kilometers) and then it probably rains frost back onto the moon’s surface.
Illustration courtesy NASA/ESA/K. Retherford/SWRI

“And most recently, the Hubble Space Telescope caught signs that Europa is sending massive plumes of water into space, akin to the explosive geysers found around Earth’s geothermal regions.” This fluidity is key to the promise of life: “In a liquid, molecules can dissolve and chemical reactions occur. [Liquid also] effectively conveys vital substances . . . from one place to another, whether it’s around a cell, an organism, an ecosystem, or a planet.”

This illustration depicts two possible cut-away views through the icy shell of Jupiter's moon Europa. (Europa, like Enceladus, also conceals a liquid ocean.) In both views, heat escapes, possibly volcanically, from Europa's rocky mantle and is carried upward by buoyant oceanic currents. Image courtesy NASA/JPL/Michael Carroll — This illustration depicts two possible cut-away views through the icy shell of Europa. In both views, heat escapes, possibly volcanically, from Europa’s rocky mantle and is carried upward by buoyant ocean currents.
Image courtesy NASA/JPL/Michael Carroll

Europa is most likely volcanic. “As on Earth, the salty ocean of Europa is sitting on top of a rocky seabed, which could be spewing heat and nutrients into the water.”

Where on Europa do scientists think life is most likely to be found? Swimming in the icy ocean? Flying through the (very) thin air? Read our interview with Emerging Explorer Kevin Hand to get an idea of what astrobiologists are looking for.
- Astrobiologists are eyeballing hydrothermal vents at the bottom of the Europan ocean. “If Europa is being tugged and pulled and squeezed through the tidal interaction with Jupiter, then there’s good reason to believe that the seafloor of Europa might be somewhat active and may host some hydrothermal vents,” says Kevin Hand. “And if Europa has hydrothermal vents, that’s a great place for providing the chemistry needed for life. So those would be the types of environments that we would want to go and explore.”
  Here is one proposal for a Europan ocean “cryobot”—an probe to explore the icy crust of the Jovian moon and its likely volcanic vents.
  Illustration courtesy JPL/NASA

Watch our video on space probes. It lists three types of probes used to explore space and gather scientific information: interplanetary probes, orbiters, and landers. What type of probe will the Europan spacecraft be?
- It will be a solar-powered orbiter, “looping . . . around the gas giant Jupiter to perform repeated close flybys of Europa over a three-year period. In total, the mission would perform 45 flybys at altitudes ranging from 16 miles to 1,700 miles (25 kilometers to 2,700 kilometers).”
  This artist’s rendering shows a concept for a spacecraft that would make multiple close flybys of Europa. The blue lines show the path of the spacecraft, and I’m pretty sure the little moon between Europa and Jupiter is the wildly volcanic Io.
  Illustration courtesy NASA/JPL-Caltech

How will scientists be looking for life on Europa?
- Trick question—they won’t be looking for life directly. They’ll be looking for data about the Europan ocean. These data will indicate the likelihood for life. The nine instruments on the spacecraft will study:
  - the geography of Europa through high-resolution mapping
  - the thickness of Europa’s icy crust
  - the salinity of the ocean (Unlike the Earth, magnesium sulfate might be a major salt component of Europa’s water or ice, while the Earth’s oceans are salty due to sodium chloride (common salt).)
  - the depth of the ocean
  - the chemistry of the ocean (how salty is it? how acidic is it?)
  - the temperatures and likely spots for vents erupting plumes of water into space
  - the composition and dynamics of Europa’s thin atmosphere
  - the composition of small particles of dust ejected from Europa