Fly Me To Which Moon? 183
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.'"
Re:We already know the outcome... (Score:5, Informative)
Interesting Mission Concepts (Score:5, Informative)
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/ [nasa.gov]
Re:access to space (Score:5, Informative)
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.
Re:WHAT ?? (Score:4, Informative)
THREE kinds of (possible) life on TITAN! (Score:3, Informative)
While the Titan mission is admittedly more ambitious (and potentially more costly) the reason why we should go to Titan is because there might be THREE radically different kinds of life there. This is from Biologist Peter Ward's book in his book "LIFE AS WE DO NOT KNOW IT".
One might be related to, or if we're not careful with contamination, might be the same as our DNA based "CHON" (Carbon, Hydrogen, Oxygen and Nitrogen) life. They would presumably live on the surface feeding on the hydrocarbons drifting down from the sky; similar to our methanogens or other chemo-trophic bacteria on earth.
Another kind of life might be something a "little" different (but still really unlike anything seen on earth, life that uses AMMONIUM as its working fluid as opposed to our life which uses water. (It would presumably live in the ammonium ocean speculated to beneath the ice) that forms Titan's surface. It's only a "little" different because it would still be basically be CHON life but who knows what its metabolism would run on?
Finally he even mentions the possibility of a SILICON based life (as opposed to our carbon based life). No, unlike the star trek Horta from "Devil in the Dark', it needn't live deep underground. Instead it would life in some of the ethane-methane lakes at the surface (which would be capable of making the silicon soluble and would substitue in for carbon I guess). So all of life's components; fats, sugars, proteins, RNA and DNA would use silicon as a major structural component. Now that's different!
For these admittedly extremely speculative reasons he suggests Titan should be on our priority list of places to visit. He recommends sending a biochemist/biochemical lab to Titan. Anyway if they found even ONE of the three kinds of life there, it would (even if they were just micro-organisms) be an incredible discovery. Of course because of Titan's distance it'll be a long while before we can put a human there, maybe we'll have to wait for A.I.
Unfortunately as much as I (and many other people including James Cameron) would love to see "black smokers" (geothermal/chemical powered undersea geysers) at Europa, Dr, Ward explains that there is just not enough energy available to Europan life (from the dim sunlight filtering through the ice or the flexing of rocky core by Jupiter's gravitational tides) to drive an ecosystem. I think he claims there would be enough to make, perhaps, 120 tons of biological matter dispersed in a volume twice that of Earth's oceans! A low flying orbiter scanning for molecular signatures in the ice or trying to capture ice crystals kicked up off the surface would likely find nothing. Even if it did find some complex organic molecules (proteins, long carbohydrates or DNA) that would be relatively indirect evidence; there would always be concern about contamination. This is in comparison to a direct observation of life on Titan, we could watch it grow!
That's why we should go to Titan, there may be a higher chance of life be present there NOW than even at Mars (recent methane plumes discoveries notwithstanding). And how cool would it be to send an orbiter AND a balloon AND a lander (or even a boat!).
Re:access to space (Score:4, Informative)
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.
Re:access to space (Score:3, Informative)
We're talking about Lagrange points relative to the Earth and Moon, not the Earth and Sun. As such, all of them are more or less the same distance as the moon.
Re:Who cares how much it costs... (Score:3, Informative)
The effect of inflation is to make dollars (in wallets, bank statements, and promissory notes) less significant compared to real goods and work products.
The effect of deflation is the opposite.
So, if you have a huge positive net worth in dollars (cash in the bank or your wallet) deflation helps you out. Those dollars become even more valuable as people desperate for work will do anything to get even a few of them from you.
However, if you have a mortgage and student loans and a big negative net worth in dollars (numbers on promissory notes) inflation is your best friend. Your work product and assets become more valuable, and your debt becomes trivial.
A few years ago my parent's mortgage payment on their 4-bedroom house was lower than my rent for a 1 bedroom apartment. That is inflation for you. Prices and wages went up so that their mortgage became a trivial cost to them since that cost was fixed.
If you are certain deflation is coming the last thing you want to do is take out a loan. The loan payments will become a bigger and bigger share of your income as your wages drop. The best thing you can do is sell your house, pay off your debt, put that cash in the bank, and rent. As your rent drops you'll be much further ahead.
Of course, if you bet on deflation and the government starts printing money look out! Your rent will soar. Just look at anybody who bought their home before the 1970s on a fixed mortgage - they cleaned up!
Re:WHAT ?? (Score:3, Informative)
Titan is a young Earth.
The chances of life not being there are incredibly low, going by what we know of the evolution of Earth and the life on it.
Because Earth, in it's early life, sported a surface temperature of -179 C, or -290 F, and as a consequence, possessed lakes of liquid hydrocarbons, and an atmosphere that was "nearly free of water vapor" (source [wikipedia.org])?
Sorry, bub, anyone who believes Titan constitutes a "young Earth" doesn't know much about either place. While Titan may possess atmopheric and geological processes that are analogous to those on Earth, it is by no means Earth-like.
Re:WHAT ?? (Score:3, Informative)
You are being hopelessly anthropocentric. If you are expecting "life" in the form of something like your dog, you are likely to be disappointed. But that doesn't imply -- at all -- that life is nonexistent there!
Re:both, plus Venus and Pluto (Score:3, Informative)
If you mean "we" humans, there were ten Soviet landers - 8 Venera, 2 Vega. Most lasted at least half an hour, some almost 2 hours.
http://nssdc.gsfc.nasa.gov/planetary/chronology_venus.html [nasa.gov]
The Unites States never attempted a landing, though one mission did send several probes into the atmosphere (they landed in the sense that a meteorite lands, but that's not what you meant).
Oh, someone re-processed the images, using modern computer technology. A great improvement over the very limited techniques of the time, they're pretty amazing:
http://www.mentallandscape.com/C_CatalogVenus.htm [mentallandscape.com]