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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.'"
Except...the Europa mission doesn't have a lander. It only has two orbiters, one would go to Europa and the other would go to Ganymede.
The Gish Bar Times - Blog covering Jupiter's moon Io
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/
The Gish Bar Times - Blog covering Jupiter's moon Io
L1, L2, and L3 are all semi-unstable points. You'd be better off in L4 or L5.
And solar wind at L1 is a bitch. At least the magnetosphere would protect some at L2.
Life disturbs local entropy. An example of which is our oxygen atmosphere which is made by living things. Excess methane on Mars and Titan has been attributed to life, but is most likely the result of natural processes.
http://michaelsmith.id.au
Umm, no. L4 and L5 are in the same orbit as the moon, and therefore at the same distance.
Not that distance is a significant factor, mind you. DeltaV requirements are the limiting factors on our ability to go places in space. DeltaV requirement to put something on the moon are about 5600 m/s, to get something to L4/5 about 4000 m/s.
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