Fly Me To Which Moon?

Hugh Pickens writes "NASA and the European Space Agency are expected later this week to settle an ongoing debate on whether to send a robotic mission to Jupiter's moon Europa or Saturn's moon Titan. Both are difficult places to get to — a mission to either would cost several billion dollars/euros to build and execute — and both have become alluring targets in the quest to learn whether Earth alone supports life. On the one hand, Europa is believed to have liquid oceans beneath its frozen crust which (on Earth at least) are a source of life-supporting chemistry. Scientists would like to scan Europa's surface for bits of material that may have seeped up from beneath the ice. 'Imagine if there were microbes entrained in material that has exuded onto the surface of Europa and they've been sitting there for maybe three million years,' says planetary scientist Dr. Brad Dalton. On the other hand, Titan has two enticing features in the search for life: liquids on the surface, and a thick atmosphere that can be used to slow down a spacecraft and help put it into orbit. Titan's surface water is locked into the crust as ice, but scientists suspect there may be a subsurface ocean where water mingles with ammonia. The mission will not get to the launch pad before 2020. 'It's unfortunate that there has to be a decision,' says NASA/JPL astrobiologist Dr. Kevin Hand. 'It's important to go to both. They are both such amazing and tantalizing worlds in terms of finding life.'"

Comments

Interesting Mission Concepts

[volcanopele]

Both the Europa and Titan mission would be very exciting missions. The Titan mission is a bit more ambitious though, with a NASA-built Titan orbiter that would map the surface at 50 meters per pixel (so not quite Google Earth resolution, but enough to define the major geologic processes that take place on Titan) and an Europe-built hot-air balloon and lander. The latter would land in the largest expanse of open liquid (methane instead of water) known outside of Earth.

The Europa mission is a bit more tame by comparison, but has a lot more technological development to back it up (which would help it come in somewhere close to its original budget). There are two orbiters. The NASA-built orbiter would explore the inner two large moons of Jupiter: Io and Europa; while the ESA-built orbiter would explore the outer two large satellites: Ganymede and Callisto. Unlike the Titan mission, no landers are planned with this mission, but the instruments on-board both spacecraft would allow it to provide more detailed global mapping of Europa and Ganymede than the Titan mission, which as mentioned before would only provide 50-m per pixel global mapping with selected areas at higher resolution imaged by the balloon (which would be limited to a relatively narrow latitude band since Titan's winds are mostly east-west).

The NASA-JPL website has a page with more detailed documents outlining the mission plans for each moon: http://opfm.jpl.nasa.gov/library/