Ophiolite

I tried to find something on the internal structure of Titan, but found nothing quantitative. We know the density averages out to 1.88 g/cc. A reasonable model that will yield this is as follows: Core: Iron-nickel 100 km radius Mantle: Rock 1800 km radius 'Crust': Ice 2575 km radius That means 65% of the volume of Titan is ice, primarily water ice. So, if we move Titan to Earth's orbit we wind up after a 'short' time with a water planet, with a global ocean 650 kms deep. After a 'longer' time, as Titan fails to retain its volatiles, we get a rocky moon half the diameter of our own.

I believe you are right. If I strain hard enough I can dimly recall the head chemistry teacher (called Gleamo, for his blindingly white lab coat) telling us of the new standard. If I'm recalling correctly it would have been '61 or '62. Just checked before posting. It was '61. Apparently till the mid 1800s it was H=1. (That one's from a website, not memory.)

Are there any grammars of whose you am awares of?

I saw my first periodic table in 1960. Imagine how I feel.

Interesting link. Thanks. A pity it makes ed84c's comment "However this is only Theory a fairly good one, but a theory non the less." look insightful. [smiles ruefully.]

Heinlein, I think, had pedal powered flying games in domes on the moon. And other authors have had their characters strap on wings in O'Neill colonies and fly around. There is also a great bit in Rendezvous with Rama by Clarke, where the hero is trapped atop a 'cliff' several hundred meters tall, that he has to get down now. (Rama, if you have not read the book is a hollow alien artifact, spinning to create an artifical gravity). He realises that with the reduced 'g' he can just junp off and hit the 'water' not much harder than a twenty foot jump on Earth. In short, low gravity would be fun. Its the high gravity we wouldn't like.

You want to go to West Texas.

Ah, I thought I had replied. The honest answer to this is that we don't know. (I take it that your last sentence is meant to read are not too great.) We would have no problem adapting to Martian gravity or lunar gravity. Could we retunr from these to Earth if we had lived there for decades, not years? That could be a najor problem, so I think you have to distinguish between exploration and colonisation. For heavier planets I imagine we could handle something like 1.2 gor 1.3g indefinitely. If we were willing to accept that we would probably never get over feeling heavy, and accepting the fact that it would likley reduce our lifespan. Now, introduce drugs, genetic engineering and the like and those problems diminish. However, we spent three billion years adapting to a 1g environment, we must expect complications when we move out of that environment. By the way, I'm not quite sure what the gotcha was for.

Are you talking about living in a desert climate, or a trek through a desert, or both. I'm just not clear exactly what you are asking. Survival in a desert can be reduced to the same fundamentals of survival anywhere: 1. Water 2. Food 3. Shelter 4. Navigation A couple of incidental points. Most deaths in the desert are due to strokes because of dehydration. Most deserts can get pretty cold at night. (No cloud cover.) You can die of hypothermia. And your friend who survived off the land, are we talking catching snakes to drink their blood, or what? I like deserts too, but I prefer to approach them in a meticulously maintained vehicle, with several spare tyres, on a main road, with lots of water. There has been a long history of cowardice in my family. Its kept us alive for generations. Anyway - take care.

Where is JFK when you need him? America needs a President with vision, not a man who has visions. I apologise if that remark offends anyone - I would rather not bring politics into a science thread, but the budget cut is a political act. When I was twelve years old I watched a news broadcast on the BBC of Kennedy making his speech at Rice University. "We choose to go to the moon in this decade, and do the other things, not because they are easy, but because they are hard." It was inspiring stuff for a young kid who already had a keen interest in dinosaurs, and planets, and aircraft. I spent the next eight years following the space program in detail. There was a time when I could have named for you each of the fifty NASA astronauts, their rank, details of flights they had made or were training for. I'd memorised the positions of every switch and dial on the Mercury capsule from a fold out in National Geographic. When the moon landing took place I was about to enter my final year of a geology degree, a route I had taken in no small measure because of my fascination with space. That America had set itself an ambitious goal, galvanised their industry and their scientists, and achieved that goal, despite setbacks along the way, I found to be truly remarkable. It generated a depth of admiration for America, Americans and the American way, that is difficult to fully describe. I hope you will excuse this personal exposition, but this cutting of the Hubble budget just seems so symptomatic of the way in which my favourite nation has lost its way. It's sad, not of itself, but for what it says about loss of vision, loss of dreams. Loss of soul.

Not at all. You can't piss geologists off. (Except by discovering one new mineral more than what they have!) I had been thinking along the lines of buggeredifiknowwhatitisite. Anyway. Tell us more about it. Hardness, colour, density, crystall class, and, of most interest, environment of formation.

I don't think anyone can be bothered going through the hassle of registering in order to be able to read the article. Can you summarise its content?

No, regretably. Remember the probe was launched seven years ago and builtwell before that, so the technology is certainly not current. The main restriction, however, was the data transfer rate that was possible. One hi-res colour photograhp and we could have kissed goodbye to most of the other data (and the other photos). Think of this as comparable with the first pictures from the flyby of Mars in the 1960s. Low res, black and white pictures of cratered terrain, that suggested that Mars was rather like the moon.

The format of the site, the tone of the text, the absence of trumpeting of the landing all say to me this is prediction/deduction from distance observations. The data is going to trickle out. ESA don't have NASA's notion of PR.

us.2u is correct in his interpretation. I was responding to encrypted's query, "why can we not have Jupiter sized Earth like planets". I was trying to demomnstrate that was like saying "why can't we have a blue that is a nice red colour?" If they could support human life they will have to be, for the reasons explained in my earlier post, similar in size to the Earth, and at the right distance from their primary. In the Solar System only Earth truly fits the bill. Venus and Mars could have made it if their distances or early histories had been a little different. The available choices to produce a viable, complex biosphere are probably quite restrictive.

Pilot's today are only on board for emergencies. You get more flying in an hour in a Cessna than several transatlantic flights at the controls of a 747. But when that emergency does arrive we can be very pleased the pilots are there.

That's standard in the industry. I suspect that with advanced avionics, fly-by-wire, etc, it will be one of the easiest craft on the planet to manage.

"During October, 1971, four cesium atomic beam clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40+/-23 nanoseconds during the eastward trip and should have gained 275+/-21 nanoseconds during the westward trip ... Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59+/-10 nanoseconds during the eastward trip and gained 273+/-7 nanosecond during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks." J.C. Hafele and R. E. Keating, Science 177, 166 (1972)

You certainly cannot have a Jupiter sized Earth like planet. [We shall ignore the obvious fact that if it is like Jupiter in size it is already very un-Earth like.] The bulk of Jupiter is made up of low density gases. You want to assemble a rocky-iron planet' date=' without these gases. The reason the Earth lacks these is that it was formed close to the sun (93 million miles is next door) and they could not condense in quantity. Those that did were progressively lost because of the weak gravitational pull. There was not enough material in the inner solar system to make anything even approaching the size of Jupiter from rocky-iron material. From what we know of other systems this would also be true. So, what if the planet formed further out and migrated inwards? Well, it would retain tthee lighter gases, so you would end up with a super-Jupiter with a really big rocky-iron core. Heh! Guess what? Lots of the planets we have found are close in super-Jupiters. Even if we could overcome these problems, you now have a planet where you would weigh several times your weight on Earth. Hardly earthlike. And plate tectonics - the key to the Earth geological character - simply could not function in an earthlike manner. I think you are refering to truly Earth like. They would:Improve our understanding of planetary and system formation Give us a figure for how common they are, and therefore improve our estimates for the abundance of life. Identify targets for SETI. Not a waste of money at all.

In another thread I notd that Using telescopes in Earth orbit planets could be searched for using direct detection methods. Stellar coronagraphs can be used to supress the light from the planet's parent star making detection easier. There is a higher probability of detecting planetary companions around nearby stars in the infrared portion of the electromagnetic spectrum. This is due to the fact that the star to planet flux ratio is less in this region of the spectrum than in the visible. To separate a planetary companion from its primary stellar halo, one must use a telescope (or array of telescopes) with an aperture (or baseline) B such that r/D is greater than or equal to the wavelength at which the observation is being carried out divided by the aperture (or baseline) of the telescope (or array of telescopes). The link I quoted from may be found here: http://www.scienceforums.net/forums/showpost.php?p=113408&postcount=68 Martin followed up with detailed information, in the following post here: http://www.scienceforums.net/forums/showpost.php?p=113505&postcount=69

It's not what?

This is quite simply the most remarkable item I have read in two decades or more. I am astounded. I checked the date on the article three times to make certain it wasn't an April Fool joke. I can't believe I have never run across this before. http://www.guardian.co.uk/life/feature/story/0,13026,1108853,00.html Some quotes in summary: Each year less light reaches the surface of the Earth. No one is sure what's causing 'global dimming' - or what it means for the future. In fact most scientists have never heard of it. Atsumu Ohmura at the Swiss Federal Institute of determined that levels of solar radiation striking the Earth's surface had declined by more than 10% in three decades. The finding went against all scientific thinking. When Ohmura eventually published his discovery in 1989 "It was ignored" . Records show that over the past 50 years the average amount of sunlight reaching the ground has gone down by almost 3% a decade. It's too small an effect to see with the naked eye, but it has implications for everything from climate change to solar power and even the future sustainability of plant photosynthesis "It's an extraordinary thing that for some reason this hasn't penetrated even into the thinking of the people looking at global climate change," says Graham Farquhar, a climate scientist at the Australian National University in Canberra. "It's actually quite a big deal and I think you'll see a lot more people referring to it." Several other research papers published during the 1990s reported that sunshine in Ireland was on the wane, that both the Arctic and the Antarctic were getting darker and that light in Japan, was falling. Levels of solar radiation reaching parts of the former Soviet Union had gone down almost 20% between 1960 and 1987. The problem is that most of the climate scientists who saw the reports simply didn't believe them. That began to change in 2001, when Stanhill and his colleague Shabtai Cohen at the Volcani Centre in Bet Dagan, Israel collected all the available evidence together and proved that, on average, records showed that the amount of solar radiation reaching the Earth's surface had gone down by between 0.23 and 0.32% each year from 1958 to 1992. And so it continues. Quite remarkable

Browse through the esa links provided. You will find answers to questions you haven't even thought of yet.