How Things Work: Europa

Jupiter’s moon Europa has been an object of fascination since 1610, when it was first discovered by Galileo.

Despite its icy appearance, Europa has proven many times to be a potential environment for the existence of extraterrestrial life.

The evidence is so compelling that it has ignited a wave of conferences, research projects, and grassroots efforts to field a space mission to Europa.

The possibility of finding extraterrestrial life on Europa’s surface seems unlikely when one considers the hostile environmental conditions that characterize the moon.

Nestled on the outskirts of the solar system, Europa faces temperatures that are too cold to sustain a body’s metabolism. Hence, Europa is often viewed as nothing more than a giant ball of ice orbiting Jupiter.

In fact, it took three fly-by missions by spacecrafts Pioneer and Voyager in 1970, and Galileo in 1995, to slowly piece together the fact that Europa harbors an astonishing secret.

Ground-based spectroscopy first revealed that Europa has an icy crust roughly that is 150 kilometers thick. Spectroscopy is the study of light wavelengths to investigate the properties of an object.

Subsequent images from Voyager revealed something further: Europa’s icy surface is crisscrossed with hundreds of intersecting ridges and bands, called “lineae.”

Furthermore, Europa’s ice surface appears to be moving. Evidence of mobile icebergs from the Galileo spacecraft confirmed this notion.

In particular, data from Galileo’s magnetometer, a device that measures magnetic fields, showed that Europa’s magnetic field flips every several hours.

This finding suggests the presence of a conductive substance on Europa’s surface, possibly  water. Researchers  suspect that this conductive substance exists three to 12 miles beneath Europa’s crust.

The icy deformations on Europa’s surface have been analyzed and reanalyzed, revealing a myriad of surface disruptions and modifications. In particular, scientists have found evidence of lenticulae (Latin for “freckles”), or brown spots that are six miles wide.

Scientists have also found pits, domes, and chaos regions atop Europa, all of which are indicative of tidal heating and crustal convection.

This evidence has inspired scientists to develop detailed models of Europa’s plumes — hot and active subsurface diapers, which are structures that rise and fall below Europa’s surface.

Scientists have also been hunting for the presence of cryovolcanoes, or volcanoes of ice, that would spew this liquid material to the surface of Europa.

Despite the strong evidence in favor of water, questions remain about the chemical composition of Europa’s putative ocean.

These questions have led researchers to seek out Europa analogs on Earth. In particular, researchers have explored bodies of ice and water in Ellesmere Island in the Canadian High Arctic, and Lake Vostok in Antarctica.

Through an interdisciplinary effort involving astronomers, geologists, biologists, physicists, chemists, and engineers, a worldview of Europa has begun to emerge.

However, probing a 150-kilometer ice shell is a mission control nightmare — unless there are areas of weakness in the enveloping crust.

This line of thinking developed into two leading models for the thickness of Europa’s ice crust: a thin-crust model (Greenberg et al., 2001) in which the crust is less than a few kilometers thick, and a thick-crust model (Pappalardo & Head, 2001) in which the crust is over 20 kilometers thick.

A further problem has arisen out of reaching the bottom of the supposed ocean on Europa’s surface Scouring out plankton or algae requires an autonomous submarine to dive under the crust and explore Europa’s depths.

In response, several projects have been launched to develop such a submarine, one of which has taken shape at Carnegie Mellon. The Deep Phreatic Thermal Explorer (DEPTHX) is an underwater robot designed to map out the Zacatón Cenote — the deepest flooded sinkhole in the world — and probe it for new and unique organisms.

While scientists continue to investigate the possibility of water existing beneath Europa’s surface, people on Earth can catch a glimpse of Europa from the comfort of their homes.
Google Maps Europa is an avant-garde mapping project put together by Georgia Tech doctoral student Peter Pesti.

A panning feature lets users seamlessly glide over Europa’s ridges, plains, and mottled terrain. The map’s magnifying tool, usually intended to zoom in on interstates, allows for endless probing and prodding of Europa’s icy landscape.

Still, the most mysterious feature of Europa lies beneath its icy exterior, just out of range of Pesti’s project.