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Galileo's Final Blaze of Glory
EccentricAnomaly writes: "CNN reports that the Galileo spacecraft is about to perform its last flyby of Io. Galileo will skim a mere 100 km above Io to enter a trajectory that crashes into Jupiter in 2003. This is to avoid the spacecraft running out of fuel and accidentally crashing into Europa which might contaminate it with any bacteria spores on Galileo. This is a real concern - Apollo 12 found bacteria on Surveyor 3 that survived two and a half years on the moon."
But they know Jupiter has an atmosphere which should burn up the probe and destroy anything on it.
A little bit risky, but if your choices are Europa or Jupiter, and you can't avoid hitting anything, you have to go with the main chance.
What I don't understand from this theory is how bacteria can survive the reentry pressure and especially heat that is generated! Or does the inside of a big enough asteroid stay cool? I wouldn't think so but does anybody have a definitive answer?
Imperium et libertas
Autocracy and freedom
If we're already spending millions of dollars on these machines, why don't we simply send em off into space in any direction taking pictures and mapping god-knows-what, then transmitting back to us until rapture? After the initial delay of sending the first image back to us, we would be getting a fairly consistent stream of images...at least until some object comes between, the signal strength wanes, or it crashes into something else (which is what it's doing now). Even the most focused spray of transmission back to us would do since as it gets further away, its transmit area would eventually cover our entire path through the solar system so that we wouldn't miss an image. I had a professor once that would probably say, "We never bring these billion-dollar toys back because those fascist, propagandizing bastards never sent em in the first place!"
...we want to be sure it is native to Europa, not imported from earth by accident in a previous space mission. This is simply good science, nothing else, and is completely orthogonal to how well, or how poorly, we are acting as stewards of the Earth.
So get off your high horse and get over yourself, saving the whales and turning our backs on technology (I notice you are using a computer, including all kinds of hydrocarbon-generated electricity and toxic materials used, and dumped, in the creation of its components) to "save the earth" really has nothing whatsoever to do with Galileo's final trajectory past Io.
The Future of Human Evolution: Autonomy
Yes, but if Jupiter did hold life, it would quite likely be accustomed to objects falling out of the sky, due to the pounding which Jupiter regularly takes (handily protecting us in the process). True, these would typically not have a nuclear reactor on board, but the main destructive energy is simply derived from the heat released upon entry into the atmosphere. Which is a fairly odd word to use about Jupiter anyway, on the basis that, as we all know, it's basically a giant gaseous pressure cooker.
Europan life might well not be so durable in such a regard as Jupiter's life might be. And furthermore, Earth bacteria have a much higher chance of surviving & growing on Europa _if_ they survived the journey and the crash than they do on Jupiter, based on our current rather limited knowledge. The actual probability of a highly specialised Earth hyperthermophile (organism which enjoys high temperatures) and hyperbarophile (organism which enjoys high pressure) making it all the way there is negligible.
"What is freedom of expression? Without the freedom to offend, it ceases to exist." Salman Rushdie
..we want to be sure it is native to Europa, not imported from earth by accident in a previous space mission. This is simply good science, nothing else, and is completely orthogonal to how well, or how poorly, we are acting as stewards of the Earth.
Certainly, the major reason for going out of our way to avoid Europa is as you say (to avoid potentially introducing life where it did not exist before.) However, I would submit that it is also "good science" to ensure that a nuclear-powered spacecraft does not crash on and contaminate a terrestrial body suspected of harboring life. This is not "save the whales environmentalism"; it is common sense. Certainly you would not call a person who was opposed to detonating a nuclear device in the atmosphere on Earth to be a "save the whales" environmentalist?
We're going down, in a spiral to the ground
Just as we have found meteorites that originated from Mars on the surface of the earth, it is a near certainty that meteors have been blasted from the surface of the Earth by asteroid impacts, possibly seeding the entire solar system with bacterial spores already. Thus, if we do find life elsewhere in the solar system, we can never be 100%, absolutely sure it did not originate on Earth. The corollary is that we cannot be absolutely sure that life on Earth did not originate somewhere else.
The large ablative surface area is to help dissipate the reentry heat, not a cause of it. It's been a while since I looked at this, but I seem to recall that the stagnation temperature for air at the leading edge of a reentry vehicle was inversely proportional to the radius of that edge. That's why the Shuttle has a nice round nosecone: they don't dare look like the Concorde or a fighter jet, because the tips of those nice sharp noses would simply melt off.
This is one of the reasons why, despite the Earth being continually pelted by thousands of tons a day of asteroidal material, it's rare that anything makes it to the ground: the small stuff just vaporizes first.
Obviously the temperature can't go to infinity, so there has to be some reason (continuum hypothesis failing at small enough distances?) why it doesn't... but even for centimeter radii leading edges we've only recently discovered ceramics that we think can survive the resulting reentry temperatures. What would let bacterial micrometer radii survive?
I think your #1 is off, too. At the very least, a bacterium reaching the Earth from another planet would have to be moving at Earth's escape velocity (because that's the velocity Earth's gravity would impart to it as it approaches), and that is 40% faster than the Shuttle's reentry velocity.
It sounds like they aren't going to send back any images from the Amalthea flyby in November. This is really idiotic -- this will be the first and *only* close flyby of that moon, and we won't get any images back, simply because they don't have the small budget it would require. Meanwhile, space station costs continue to spiral out of control, and just try to name *one* scientific discovery the space station has contributed to.
Looks like it's time to email / call / write your member of Congress.
Yeah, but I think the important thing here is that EARTH bacteria couldn't survive there, whereas they might survive on Europa.
What, you people think life is impossible on Jupiter? We don't know enough to say one way or the other. Who's to say Galileo's bacteria won't have some drastic effect on some Jovian life we are currently unaware of? Why contaminate Jupiter to save Europa from contamination? Why not just fling Galileo into the depths of space or into the sun if we want to get rid of it?
This smells to me of either not having been carefully thought through, or of unthinking assumptions that life must be impossible on Jupiter, when we simply don't know.
-Kasreyn
Kasreyn: Cheerfully playing the part of Devil's Advocate to hairtrigger