NYTimes article on Galileo probe

C. E. Sum writes "The New York Times is running a very nice article this morning on the past, present, and future of the Galileo space probe. Overcoming a few problems early on, the probe has gone on to a long and prosperous mission. There is a lot of talk about the current survey of Jupiter's moons, including some really neat pictures of volcanos on Io. The probe has lasted twice as long as the original engineers thought, and probably has at least another year of life in it. "

Comments

Random questions

[re-geeked]

The longer-term plan mentions more trips to Io and Ganymede. What about Callisto? That news (of a possible ocean) seemed the most surprising.

Could the communications system be (ab)used as radar to check for a Europan ocean? Probably too weak and/or wrong frequency.

Is the Jovian radiation even necessary to provide energy for life on Europa? Wouldn't the ambient heat of the ocean water be enough, especially near the ocean floor, where the chemistry and geology would get most interesting? What would early indications of volcanism on Europa look like -- discoloration of surface ice?

Guesses are as welcome as informed responses.

One last question: is this thing on?

Re:Random questions

[v0rteck]

I'm so glad to read about the fantastic success of Galileo, and the great scientific results it is producing. I remember, as a child, sitting at my TRS-80 downloading articles from the local planetarium's BBS at 300 baud about the upcoming launch of Galileo. I read about it's trajectory, VEEGA (Venus-Earth-Earth Gravity Assist) long before I had any idea how a gravity assist worked.

I would like to see more flybys of Callisto too. Of course, if the mission gets extended another 14 months, surely there'll be time for study of Callisto in addition to the other 3 big moons.

Good idea about re-engineering the communication system. However, I'd bet the transmitter couldn't send pings powerful enough to get any discernible data, especially with the problems it's had (failure of the main antenna to unfurl). The magnetic disturbances the probe detected are a damn good indicator of a conducting (salt-water) sphere, though. As sophomore physics teaches us, a conductor naturally cancels any magnetic field it's embedded in. So when the probe detects a weakened field around the moon, you can deduce that the moon has a conducting sphere.

As for energy to support life, I tend to agree with you. Europa's proximity to Jupiter, as well as resonance with Io and Ganymede, cause a lot of tidal flexing, and this flexing generates a lot of heat. Enough heat to allow water to exist in a liquid state, IMHO, would be enough heat to support single-celled organisms.

I really enjoyed this Times article. It referred to the Scientific American article, which turns out to be available online here. Check it out. More great details and more pretty pictures!

Re:Random questions

[re-geeked]

What I remember is the 2am "Neptune at Night" or some such thing that the local PBS station picked up. The first pictures of Triton were spectacular. Is there any such broadcast to be found for Galileo?

Re:Random questions

[Anomalous Canard]

Is the Jovian radiation even necessary to provide energy for life on Europa? Wouldn't the ambient heat of the ocean water be enough, especially near the ocean floor, where the chemistry and geology would get most interesting?

Without some external source of energy, Europa would have frozen solid long ago. The external source prior to Gallileo was thought to be tidal stresses in the crust -- the same source that powers Io's vulcanism. The radiation readings, while also providing indirect evidence for liquid water on Europa, also provides a means to excite the chemicals likely present in the water to unusual forms that might tend to create "organic" substances.
Anomalous: inconsistent with or deviating from what is usual, normal, or expected

Re:Random questions

[re-geeked]

I don't think the recent radiation findings undermine the belief that Europa's ocean is heated by tidal forces. Rather, I was wondering why this additional energy source was being touted as a necessary energy source for life. Or were the journalists misspeaking, and the radiation only helps explain exotic chemical reactions?

Re:Random questions

[Captn Pepe]

You can find the Galileo project's Galileo Millennium Mission on the JPL's pages. Tentatively, there aren't any close flyby opportunities of Callisto scheduled for this extended-extended mission, although there is growing support within NASA to send one of the "faster-better-cheaper" probes to take a closer look. The Europa Orbiter is such a probe that would look closer at the suspected ocean there, so a misson to other Jovian satellites is not out of the question.

In theory, you could have Galileo transmit to Earth at a time when Calisto would be passing between the probe and us; however, such an event isn't likely to occur if a close flyby isn't scheduled, and even if one was, an occultation still isn't a guarantee. And unfortunately, Galileo isn't set up to, for instance, use its antenna as a reflection radar to look for itself. Passive sensors only.

As far as Jovian radiation goes, I would propose that, given current theories regarding life's evolution on Earth, it would increase the probability that life would arise. Besides a fertile chemical environment, it seems that ionizing radiation accelerates the process of dissociating simple molecules which can then recombine into more complex ones. Background radiation in interstellar space is enough to form alcohols in nebulae and amino acids and PAHs in cometary ice; stellar radiation or Jupiter's radiation belts would do this even faster. That said, the ice crust on top of Europa's ocean is probably thick enough to shield any incoming ionizing radiation, so it's likely a non-issue. Life's best bet on Europa is tidally-generated heat and geologic radiation.

Discoloration, meanwhile, suggests eruptions, but smooth, crater-free regions are better evidence of this. Of course, cratering doesn't tell us much more than that volcanism happened within the last half-billion years or so. What appear to be fresh escarpments along fault lines might bring that date a little closer, but discoloration is going to really clinch the issue, once we know what the stuff is. For this, we need the Europa Orbiter to do spectral analysis on the surface. If it turns out to be, for instance, sulpher or iron-rich minerals from the ocean underneath, we don't get much new information about the age of the eruptions. If we're looking at some sort of hydrocarbonish gunk, it would be broken down by radiation rather quickly, so it is more recent. Most exciting of all, it could be some sort of organic residue from subsurface life forms ... but who knows.

Test Galileo and make the next probes better.

[Louis_Wu]

Galileo has outlasted the estimates of its lifespan, and I'm sure the project engineers are anxious to find out why, and more importantly, how to make the next probe more rugged. These types of probes are hard to test (zero-gravity test chamber, cosmic ray emitters, micro-meteroids, super-strong magnetic fields), so lessons about unpredicted behaviors must be learned from the previous missions. This mission has tremendous potentional to teach us about spacecraft performance in environments other than near-Earth (Hello Moon/Mars missions!), and machine performance near Jupiter (Hello colonization of Ganymede!). Oh, yeah, the science in studying Europa is important too. ;) I think that NASA should continue the Galileo mission as long as the spunky little girl will keep on keeping on, if only to tell engineers how to make better spacecraft.

Louis Wu

Re:Test Galileo and make the next probes better.

[re-geeked]

I'm not sure that there's anything to learn about the expected lifetime, as it seems to have just got lucky in terms of which electronics have or have not failed due to radiation, etc.

Although it does teach the lesson that if a probe can still talk, hear, see, and manuever, even in limited ways, it can still be extremely useful. The most shameful thing would be to end the mission prematurely because we didn't expect to spend this much time and money supporting it.

Re:Test Galileo and make the next probes better.

[Louis_Wu]

Good point; it seems Galileo would be a great partner if I were going to gamble in Las Vegas. However, that doesn't mean that the engineers didn't do something right without knowing it. Sometimes the most trivial, seemingly unrelated information is the crucial key to solving the problem.

I recall (but can't support) that an early physicist was conducting experiments to determine the speed of light, but his numbers were way off. He checked his instruments several times, re-checked the procedure, and still couldn't find the problem. He forgot to measure the length of the room he was conducting his experiments in; the light beam he was measuring was bouncing off of the walls before he measured it again. If he had realized what was happening, he could have accounted for the reflections more precisely.

Engineering is sometimes more art than science, and more so on the edges of the envelope. The new, untried situations are where an engineer's intuition and experience can shine brightest. But that shine rarely illuminates the situation perfectly, and improvements can always be made. We can't test our space probes in environments which correspond in any way to the environments they will experience in service, so why not test one while it is in service?

As an example of why we need to test things where we will use them, take a bar of steel and bend it. Leave that bar of steel out in an Alaskan winter. Then bend it again. It won't behave the same: it will be more brittle, fatigue weakens the crystalline structure, and you won't want to trust it ever again. ASME has an entire division devoted to Arctic Engineering, and people have lived there for centuries.

One of the hallmarks of engineering in situations where there isn't extensive experience is the acquisition and application of test data. Even where we have experience, test data is a necessity if the applicable theories are not precise or reliable enough.

Fatigue (The gradual weakening of a part [usually metal] over time. Try to break a paper-clip, you probably can't. Bend it two dozen times, it will probably break.) is a good example of an area where we have decades of experience, and we still need good test data for many situations. We need this test data. Maybe not now, but when 15 people are in the third month of a 5 year Mars mission, they will want everything to have been thoroughly tested. We can start with Galileo.

I think that the Galileo mission should be extended, both for the science, and the engineering of future spacecraft.

Louis Wu