Why is europa so intriguing to astronomers

Showman and R. Malhotra, "The Galilean Satellites," Science 77, Since its discovery in , Europa—one of Jupiter's four large moons—has been an object of interest to astronomers and planetary scientists. Much of this interest stems from observations made by NASA's Voyager and Galileo spacecraft and from Earth-based telescopes indicating that Europa's surface is quite young, with very little evidence of cratering, and made principally of water ice.

More recently, theoretical models of the jovian system and Europa have suggested that tidal heating may have resulted in the existence of liquid water, and perhaps an ocean, beneath Europa's surface. NASA's ongoing Galileo mission has profoundly expanded our understanding of Europa and the dynamics of the jovian system, and may allow us to constrain theoretical models of Europa's subsurface structure.

Meanwhile, since the time of the Voyagers, there has been a revolution in our understanding of the limits of life on Earth. Life has been detected thriving in environments previously thought to be untenable—around hydrothermal vent systems on the seafloor, deep underground in basaltic rocks, and within polar ice. Elsewhere in the solar system, including on Europa, environments thought to be compatible with life as we know it on Earth are now considered possible, or even probable.

Spacecraft missions are being planned that may be capable of proving their existence. Against this background, the Space Studies Board charged its Committee on Planetary and Lunar Exploration COMPLEX to perform a comprehensive study to assess current knowledge about Europa, outline a strategy for future spacecraft missions to Europa, and identify opportunities for complementary Earth-based studies of Europa.

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Do you enjoy reading reports from the Academies online for free? Sign up for email notifications and we'll let you know about new publications in your areas of interest when they're released. Get This Book. Visit NAP. Looking for other ways to read this? No thanks. Suggested Citation: "1 Why Europa?. A Science Strategy for the Exploration of Europa.

Page 8 Share Cite. Page 9 Share Cite. Page 10 Share Cite. Box 1. Page 11 Share Cite. Page 12 Share Cite. These phases encompass the following activities: Satellite tour. Page 7 Share Cite. Login or Register to save! Stay Connected! But Europa is unique. Not only is its crust relatively thin, but its surface is covered with thousands of narrow, criss-crossing ridges and crevices, some extending for hundreds of miles. Unlike its neighbors, which have pockmarked appearances thanks to being pummeled by comets and asteroids for eons, Europa has few craters to show for its age.

Somehow the moon is continually giving itself a facelift, and its many ridges could be involved in covering or erasing such craters over time, Babcock and their colleagues argue. To definitively answer any of these questions, however, requires new space missions.

Europa was last visited by a dedicated spacecraft—named in honor of its discoverer, Galileo—two decades ago. It made close passes by the moon and its neighbors and took images with its cameras in the process. Before that, Voyager 2 snapped photos as it flew by in By observing the intensities of radiation-induced light emitted by the surface, Europa Clipper could build a composition map of the moon.

Earth-bound telescopes have observed Europa in the visible spectrum before, including the Keck Observatory and the Hubble Space Telescope, but no significant emissions were detected. However, the large distances between the Earth and Europa may be partially to blame. From low altitude — just 50 kilometres above the surface — the Europa Clipper mission has a better chance. These measurements could give us a better understanding of the sub-surface ocean, placing constraints on properties such as salinity.

Looking further forward, they could also help identify the most interesting places on Europa to visit. Lauren Fuge is a science journalist at Cosmos.