Solar System Uranium Measure

Enthusiasm for the metal content of space debris is a little misplaced but it is nice to get these estimates to play with. As posted here before, these are hardly a source of wealth.

In fact, it all needs the massive contribution of water inside a gravity well in order to generate the heat and chemistry needed to concentrate metals in economically usable amounts.

It is obvious that the Earth is likely a very good sample of what is actually up there. Unfortunately the process of geology has obscured the actual metal content for elements like uranium and thorium. Most is surely in the core and we have no way of believably determining how much as yet.

The claim is also made that the content of the Oort cloud is fairly small. I see no reason whatsoever to make that assumption. In fact I am quite happy to make the opposite conjecture that the mass of the Oort cloud approaches that of the inner solar system. The evidence supports neither, and until we get out there and get a real look at the content we simply do not know. We do know that a huge dust halo was the original starting point and that it led to the creation of Jupiter which collected the material of the inner solar system. This machine led to the pumping out of the smaller planets while this scouring took place.

The real surprise to me is that the Oort cloud may be largely formed from pure carbon. Or perhaps more plausibly, the electric aspects of carbon allow it to be more actively collected and disturbed into a near solar orbit. We are finding our share of Pluto like bodies out there and they are not coming for a trip through the solar system. In fact, if the observed part of the Oort cloud happens to be only the carbon and the same proportions of other elements are similar to earth then the conjecture that I just made over relative masses is just about right.

In the event, the spatial volume of the outer solar system is many times greater than the volume of the inner system so there is ample space to stuff things and not have them attracting each other very well. All I am saying is that if we took the known planets and ground them into dust and placed them in the Oort cloud we would likely be unable to tell the difference.

August 08, 2009

How Much Uranium is in the Solar System ?

http://nextbigfuture.com/2009/08/how-much-uranium-is-in-solar-system.html

We don't know the composition of the asteroids or the objects in the Oort comet cloud or the Kuiper belt in great detail. One theory of solar system formation is that there are more metals in the inner solar system. That would mean most of the uranium is Mars, Mercury, Earth Venus and asteroid belt. There is an estimated 40 trillion tons of Uranium and 120 trillion tons of thorium in the Earth's crust. Most of that Uranium is concentrated in the continental crust. The mantel has lower concentration of uranium, but there is a lot more mantel and mantel recycles out to crust.

The solar heavy-element abundances described above are typically measured both using spectroscopy of the Sun's photosphere and by measuring abundances in meteorites that have never been heated to melting temperatures. These meteorites are thought to retain the composition of the protostellar Sun and thus not affected by settling of heavy elements. The two methods generally agree well.

Meteors tend to only have 0.008 ppm uranium

The Sun is 332,830 earth masses. So if the Sun was 8 ppb (parts per billion) uranium, then 0.27% of an earth mass of uranium in the Sun.

The National Physics laboratory (UK) has an estimate of the amount of all elements in the sun, solar system, meteorites, crust and ocean

0.018 atoms of uranium out of every 30 billion atoms in the solar system. 1 out of 5 billion by weight (1/40th of the meteor estimate). Then about 0.005% of an earth mass of Uranium.

99.8% of the total mass of the Solar System is the Sun. So the Uranium that is not in the Sun in the solar system is 500 times less than 0.005% of an earth mass [1/ten millionth of an earth mass]. One earth mass is 5.9742 × 10^21 tons. So 6 x 10^14 tons of Uranium. An estimate of 600 trillion tons or 12 times the amount in the earth's crust for Uranium not in the Sun in the solar system.

There definitely is a lot of metal (iron, platinum) in the asteroids.

One NASA report estimates that the mineral wealth of the asteroids in the asteroid belt might exceed $100 billion for each of the six billion people on Earth. John S. Lewis, author of the space mining book Mining the Sky, has said that an asteroid with a diameter of one kilometer would have a mass of about two billion tons. There are perhaps one million asteroids of this size in the solar system. One of these asteroids, according to Lewis, would contain 30 million tons of nickel, 1.5 million tons of metal cobalt and 7,500 tons of platinum. The platinum alone would have a value of more than $150 billion.

The outer Oort cloud is believed to contain several trillion individual comet nuclei larger than approximately 1.3 km (about 500 billion with absolute magnitudes brighter than 10.9), with neighboring comets typically tens of millions of kilometres apart. Its total mass is not known with certainty, but, assuming that Halley's comet is a suitable prototype for all comets within the outer Oort cloud, the estimated combined mass is 3 × 10^25 kilograms, or roughly five times the mass of the Earth.

Models predict that the inner cloud should have tens or hundreds of times as many cometary nuclei as the outer halo; it is seen as a possible source of new comets to resupply the relatively tenuous outer cloud as the latter's numbers are gradually depleted

The collective mass of the Kuiper belt is relatively low. The upper limit to the total mass is estimated at roughly a tenth the mass of the Earth, with some estimates placing it at a thirtieth an Earth mass.

There is uranium and thorium on Mars

There is uranium on the moon.

Several of the larger moons in the solar system and planets could have substantial percentages of uranium in their cores. There is a controversial theory that there is a lot of Uranium in planetary cores. Some spectral analysis of the surface of some solar bodies a couple of sampling missions and guesses at what is in the core of objects is what we are going on.

Comet Catastrophes Unlikelier

Not so fast folks. While a comet can intercept the earth’s orbit it is also most likely to end up impacting Jupiter. However impacting the Earth is a probable event however minor. That a full impact is very unlikely is welcome news that also makes the Pleistocene nonconformity much more anthropogenic. We added another few millions of zeros to the probability measure. It is now about one chance in a billion or so to get hit at all times the one chance in a billion to hit it on the bull’s eye.

The main effect of a comet strike is kinetic energy transfer to the crust but naturally spread out as it will have broken up, and also a killing shock wave that will need an entire continent to properly attenuate. We will also have a major injection of soot and a lot of frozen methane, water and whatever else.

A comet strike is thus an excellent way to eliminate large animals that are simply too fully exposed while deer in a coulee can be amply protected. Decimation of large carnivores may simply have been too much for their recovery if human predation quickly recovered also.

We can make one assertion at least. A comet strike will leave a thin layer of carbon in the fossil record. It may be possible to separate its origins from organic carbon.

What we do know is that a major strike is unlikely even though a small strike like Tunguska is likely very common. We could have one per year over the Pacific and no one would be the wiser. I suspect that we do not even measure atmospheric soot at the moment

Acquitting Comets Of Catastrophes

by Staff Writers
Moffett Field CA (SPX) Aug 05, 2009

http://www.spacedaily.com/reports/Acquitting_Comets_Of_Catastrophes_999.html

Scientists have long debated the role of asteroid and comet impacts in mass extinctions on Earth. New research may indicate that it is highly unlikely that comets caused any mass extinctions. The findings could have implications in determining the likelihood of globally-damaging impacts in our planet's future.
Scientists have debated how many mass extinction events in Earth's history were triggered by a space body crashing into the planet's surface. Most agree that an asteroid collision 65 million years ago brought an end to the age of dinosaurs, but there is uncertainty about how many other extinctions might have resulted from asteroid or comet collisions with Earth.

In fact, astronomers know the inner solar system has been protected at least to some degree by Saturn and Jupiter, whose gravitational fields can eject comets into interstellar space or sometimes send them crashing into the giant planets. That point was reinforced last week (July 20) when a huge scar appeared on Jupiter's surface, likely evidence of a comet impact.

New University of Washington research indicates it is highly unlikely that comets have caused any mass extinctions or have been responsible for more than one minor extinction event. The work also shows that many long-period comets that end up in Earth-crossing orbits likely originate from a region astronomers have long believed could not produce observable comets. A long-period comet takes from 200 years to tens of millions of years to make a single orbit of the sun.

"It was thought the long-period comets we see just tell us about the outer Oort Cloud, but they really give us a murky picture of the entire Oort Cloud," said Nathan Kaib, a University of Washington doctoral student in astronomy and lead author of a paper on the work being published July 30 in Science Express, the online edition of the journal Science. NASA and the National Science Foundation funded the work.

The Oort Cloud is a remnant of the nebula from which the solar system formed 4.5 billion years ago. It begins about 93 billion miles from the sun (1,000 times Earth's distance from the sun) and stretches to about three light years away (a light year is about 5.9 trillion miles). The Oort Cloud could contain billions of comets, most so small and distant as to never be observed.

There are about 3,200 known long-period comets. Among the best-remembered is Hale-Bopp, which was easily visible to the naked eye for much of 1996 and 1997 and was one of the brightest comets of the 20th century. By comparison, Halley's comet, which reappears about every 75 years, is perhaps the best-known comet, but it is a short-period comet, most of which are believed to originate in a different part of the solar system called the Kuiper Belt.

It has been believed that nearly all long-period comets that move inside Jupiter to Earth-crossing trajectories originated in the outer Oort Cloud. Their orbits can change when they are nudged by the gravity of a neighboring star as it passes close to the solar system, and it was thought such encounters only affect very distant outer Oort Cloud bodies.

It also was believed that inner Oort Cloud bodies could reach Earth-crossing orbits only during the rare close passage of a star, which would cause a comet shower. But it turns out that even without a star encounter, long-period comets from the inner Oort Cloud can slip past the protective barrier posed by the presence of Jupiter and Saturn and travel a path that crosses Earth's orbit.

In the new research, Kaib and co-author Thomas Quinn, a UW astronomy professor and Kaib's doctoral adviser, used computer models to simulate the evolution of comet clouds in the solar system for 1.2 billion years. They found that even outside the periods of comet showers, the inner Oort Cloud was a major source of long-period comets that eventually cross Earth's path.

By assuming the inner Oort Cloud as the only source of long-period comets, they were able to estimate the highest possible number of comets in the inner Oort Cloud. The actual number is not known. But by using the maximum number possible, they determined that no more than two or three comets could have struck Earth during what is believed to be the most powerful comet shower of the last 500 million years.

"For the past 25 years, the inner Oort Cloud has been considered a mysterious, unobserved region of the solar system capable of providing bursts of bodies that occasionally wipe out life on Earth," Quinn said. "We have shown that comets already discovered can actually be used to estimate an upper limit on the number of bodies in this reservoir."

With three major impacts taking place nearly simultaneously, it had been proposed that the minor extinction event about 40 million years ago resulted from a comet shower. Kaib and Quinn's research implies that if that relatively minor extinction event was caused by a comet shower, then that was probably the most-intense comet shower since the fossil record began.

"That tells you that the most powerful comet showers caused minor extinctions and other showers should have been less severe, so comet showers are probably not likely causes of mass extinction events," Kaib said.

He noted that the work assumes the area surrounding the solar system has remained relatively unchanged for the last 500 million years, but it is unclear whether that is really the case. It is clear, though, that Earth has benefitted from having Jupiter and Saturn standing guard like giant catchers mitts, deflecting or absorbing comets that might otherwise strike Earth.

"We show that Jupiter and Saturn are not perfect and some of the comets from the inner Oort Cloud are able to leak through. But most don't," Kaib said. The results of the study shed light on how comet impacts could have affected Earth's biosphere in the past, and also help astrobiologists understand the liklihood of comet impacts affecting the future of life on Earth.