What Would We Want to Know if We Landed on Europa Today?

Most of what scientists know of Jupiter’s moon Europa they have gleaned from a dozen or so close flybys from NASA’s Voyager 2 spacecraft in 1979 and NASA’s Galileo spacecraft in the mid-to-late 1990s. Even in these fleeting, paparazzi-like encounters, scientists have seen a fractured, ice-covered world with tantalizing signs of a liquid water ocean under its surface. Such an environment could potentially be a hospitable home for microbial life. But what if we got to land on Europa’s surface and conduct something along the lines of a more in-depth interview? What would scientists ask? A new study in the journal Astrobiology authored by a NASA-appointed science definition team lays out their consensus on the most important questions to address.

“If one day humans send a robotic lander to the surface of Europa, we need to know what to look for and what tools it should carry,” said Robert Pappalardo, the study’s lead author, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “There is still a lot of preparation that is needed before we could land on Europa, but studies like these will help us focus on the technologies required to get us there, and on the data needed to help us scout out possible landing locations. Europa is the most likely place in our solar system beyond Earth to have life today, and a landed mission would be the best way to search for signs of life.”

This view of Jupiter’s moon Europa features several regional-resolution mosaics overlaid on a lower resolution global view for context. The regional views were obtained during several different flybys of the moon by NASA’s Galileo mission, and they stretch from high northern to high southern latitudes. Prominent here are the long, arcuate (or arc-shaped) and linear markings called lineae (Latin for strings or threads), which are a signature feature of Europa’s surface. Color saturation has been enhanced to bring out the subtle red coloration present along many of the lineae. The color data extends into the infrared, showing bluish ice (indicating larger ice grains) in the polar regions.

The terrain in this view stretches from the side of Europa that always trails in its orbit at left (west), to the side that faces away from Jupiter at right (east). In addition to the lineae, the regional-scale images contain many interesting features, including lenticulae (small spots), chaos terrain, maculae (large spots), and the unusual bright band known as Agenor Linea in the south.

The regional-resolution mosaics enhance the amount of detail visible in a previously released view of the same region on Europa, [see PIA02590]. While the earlier image uses much of the same low-resolution data, its images are projected from a different angle and are processed with greater color saturation.

This view is an orthographic projection centered on 5.53 degrees south latitude, 214.5 degrees west longitude and has a resolution of 1600 feet (500 meters) per pixel. An orthographic view is like the view seen by a distant observer looking through a telescope.

The mosaic was constructed from individual images obtained by the Solid State Imaging (SSI) system on NASA’s Galileo spacecraft during six flybys of Europa between 1996 and 1999 (flybys designated G1, E11, E14, E15, E17, and E19). Image Credit: NASA/JPL-Caltech/University of Arizona

The paper was authored by scientists from a number of other NASA centers and universities, including the Johns Hopkins University Applied Physics Laboratory, Laurel, Md.; University of Colorado, Boulder; University of Texas, Austin; and the NASA Goddard Space Flight Center, Greenbelt, Md. The team found the most important questions clustered around composition: what makes up the reddish “freckles” and reddish cracks that stain the icy surface? What kind of chemistry is occurring there? Are there organic molecules, which are among the building blocks of life?

Additional priorities involved improving our images of Europa – getting a look around at features on a human scale to provide context for the compositional measurements. Also among the top priorities were questions related to geological activity and the presence of liquid water: how active is the surface? How much rumbling is there from the periodic gravitational squeezes from its planetary host, the giant planet Jupiter? What do these detections tell us about the characteristics of liquid water below the icy surface?

“Landing on the surface of Europa would be a key step in the astrobiological investigation of that world,” said Chris McKay, a senior editor of the journal Astrobiology, who is based at NASA Ames Research Center, Moffett Field, Calif. “This paper outlines the science that could be done on such a lander. The hope would be that surface materials, possibly near the linear crack features, include biomarkers carried up from the ocean.”

This work was conducted with Europa study funds from NASA’s Science Mission Directorate, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena.

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