Are we alone in the Universe? This question has worried philosophers and scientists alike for hundreds of years. Though we still hear only silence when looking out into the stars, an upcoming NASA mission may help solve the mystery of life beyond Earth.
It all starts with Europa – the fourth-largest moon of Jupiter and one of the most promising candidates for the search for extraterrestrial life. First identified by Galileo in the early 17th century, Europa didn’t seem all that interesting for most of its history. This changed in the 1970’s, when the two Voyager spacecraft marked the beginning of a continuing series of missions to the outer Solar System. Since then, the moon has been observed by many spacecrafts, the most detailed data coming from NASA’s Galileo, which arrived at Jupiter in 1995. Altogether, their data forms an intriguing image: an ocean world covered by a 10-30 kilometer (6-19 mile) thick layer of ice, protected from the freezing temperatures of space, and warmed by the tidal forces of Jupiter. Recent observations have also suggested the possibility of geyser-like eruptions of water from the subsurface ocean into the moon’s thin atmosphere. Scientists imagine that this ocean could provide an environment hospitable to the emergence of life – after all, life here on Earth started deep underwater.
Still, there’s a lot we don’t know about Europa. What is the structure of the subsurface ocean, its depth, composition? How deep does it go? What is the nature of the ice covering the ocean? What processes have shaped it in the past and continue to do so today? And, of course, is it home to previously unseen forms of life? NASA plans to attempt to answer some of these questions with Europa Clipper, an upcoming probe set to be launched in the 2020’s. This mission is the realization of NASA’s longstanding desire to visit Europa, which started after the subsurface ocean was first identified by the Galileo spacecraft in the 1990’s. Since then, several versions of a Europa explorer have been proposed, culminating in the choice of a multiple-flyby Jupiter orbiter, called “Europa Clipper” in reference to the clipper ships of the 19th century, in the early 2010’s. The orbiter’s elliptical orbit will allow it to complete 45 close flybys of the moon. A total of nine distinct instruments on board will gather new and exciting data, among these: The Plasma Instrument for Magnetic Sounding (PIMS) and Interior Characterization of Europa using Magnetometry (ICEMAG), which will work together to determine the structure and depth of Europa’s ocean and map its features through detailed analysis of the moon’s magnetic field; the Europa Imaging System (EIS), which will generate a detailed map of the moon’s icy surface, while the Europa Thermal Emission Imaging System (E-THEMIS) locates areas of increased thermal activity, such as geysers; The MAss SPectrometer for Planetary EXploration/Europa (MASPEX) and SUrface Dust Mass Analyzer (SUDA), which will determine the composition of Europa’s surface, ocean, and atmosphere.
Though Europa Clipper will likely not answer the age-old question of extraterrestrial life, it is a crucial step in that direction. With more detailed observations of the icy moon, it will be easier to obtain funding for follow-up missions. Ultimately, planetary scientists hope to launch a lander, perhaps even one that could drill through the icy crust and explore the ocean below, bringing us ever closer to the discovery of life elsewhere in our Solar System.