APOD: Cassini's Grand Finale Tour at Saturn (2017 Jan 25)

[Javachip3]

Ann (and Neufer), I did indeed insert those all-caps bold-face words inside Neufer's quote, as is common practice when replying to a post in online forums. After I posted my reply and saw how it looked, I saw that there was the potential for misunderstanding, so I attempted to edit or delete my post, but could not find a way to do either of those things as a guest user. Thank you for allowing me to clarify.

[Ann]

Ann (and Neufer), I did indeed insert those all-caps bold-face words inside Neufer's quote, as is common practice when replying to a post in online forums. After I posted my reply and saw how it looked, I saw that there was the potential for misunderstanding, so I attempted to edit or delete my post, but could not find a way to do either of those things as a guest user. Thank you for allowing me to clarify.

Thanks for explaining.

Ann

[Javachip3]

...Almost certainly, there is something on the order of 100 trillion kilograms of U-238 in Saturn, which means that plutonium is continuously being created, in quantities that dwarf the 33 kg that will be introduced by the RTG burning up.

There is a lot of uncertainty in that estimate. But even if it is accurate, then using a uranium:plutonium ratio of a trillion, there could be on the order of 100 kg plutonium on Saturn pre-Cassini, and 33 kg does not seem so trivial.

I belabor this point because the thought process that we use to give ourselves permission to dump a highly hazardous material on Saturn is the same thought process that we have used to degrade and pollute our environment on Earth.

[neufer]

...Almost certainly, there is something on the order of 100 trillion kilograms of U-238 in Saturn, which means that plutonium is continuously being created, in quantities that dwarf the 33 kg that will be introduced by the RTG burning up.

There is a lot of uncertainty in that estimate. But even if it is accurate, then using a uranium:plutonium ratio of a trillion, there could be on the order of 100 kg plutonium on Saturn pre-Cassini, and 33 kg does not seem so trivial.

It is probably more reasonable to assume that from the ~100 trillion kilograms of U-238 in Saturn's hot dense core perhaps ~100 kilograms of P-238 are produced each year. With a half life of ~100 years that should result in ~20,000 kilograms of P-238. In any event, concern about trashing anyplace that is devoid of any real possibility of life is misplaced.

<<The Holocene extinction, otherwise referred to as the Sixth extinction or Anthropocene extinction, is the ongoing extinction event of species during the present Holocene epoch mainly due to human activity. The large number of extinctions span numerous families of plants and animals including mammals, birds, amphibians, reptiles and arthropods. with widespread degradation of highly biodiverse habitats such as coral reefs and rainforest, as well as other areas, the vast majority are thought to be undocumented. According to the species-area theory and based on upper-bound estimating, the present rate of extinction may be up to 140,000 species per year, making it the greatest loss of biodiversity since the Cretaceous–Paleogene extinction event.

The Holocene extinction includes the disappearance of large land animals known as megafauna, starting at the end of the last Ice Age. Megafauna outside of the African continent, which did not evolve alongside humans, proved highly sensitive to the introduction of new predation, and many died out shortly after early humans began spreading and hunting across the Earth (additionally, many African species have also gone extinct in the Holocene). These extinctions, occurring near the Pleistocene–Holocene boundary, are sometimes referred to as the Quaternary extinction event.

The arrival of humans on different continents coincide with megafaunal extinction. The most popular theory is that human overhunting species added to existing stress conditions. Although there is debate on how much human predation affected their decline, certain population declines have been directly correlated with human activity, such as the extinction events of New Zealand and Hawaii. Aside from humans, climate change may have been a driving factor in the megafaunal extinctions, especially at the end of the Quaternary.

The ecology of humanity has been noted as being that of an unprecedented "global superpredator" that regularly preys on the adults of other apex predators and has worldwide effects on food webs. Extinctions of species have occurred on every land mass and ocean, with many famous examples within Africa, Asia, Europe, Australia, North and South America, and on smaller islands. Overall, the Holocene extinction can be characterized by the human impact on the environment. The Holocene extinction continues into the 21st century, with meat consumption, overfishing, ocean acidification and the amphibian crisis being a few broader examples of an almost universal, cosmopolitan decline in biodiversity. A ballooning human population along with profligate consumption are considered to be the primary drivers of this rapid decline.>>

[Chris Peterson]

...Almost certainly, there is something on the order of 100 trillion kilograms of U-238 in Saturn, which means that plutonium is continuously being created, in quantities that dwarf the 33 kg that will be introduced by the RTG burning up.

There is a lot of uncertainty in that estimate. But even if it is accurate, then using a uranium:plutonium ratio of a trillion, there could be on the order of 100 kg plutonium on Saturn pre-Cassini, and 33 kg does not seem so trivial.

It's more a question of whether there are tens of thousands of kilograms or millions of kilograms. But it doesn't matter. Even if there was zero plutonium on Saturn, adding 33 kg of it is utterly trivial.

I belabor this point because the thought process that we use to give ourselves permission to dump a highly hazardous material on Saturn is the same thought process that we have used to degrade and pollute our environment on Earth.

Why shouldn't we "give ourselves permission"? Saturn is ours to do with what we will. The only real responsibility we have is to ensure that we don't somehow damage it in a way that makes it harder for us to understand in the future (something we probably lack the capacity to do at this point). We have three options. We can not go at all, which is completely unacceptable. We can leave the probe in orbit where there's a real chance it will eventually hit a moon, which is scientifically irresponsible. Or we can dispose of the probe in Saturn, an action that has no negative consequences at all (as determined by people who know a lot more about this subject than you do).

[justaguy]

I know that it is nothing particular, but anyway: Sept 15, 2017 is my 50th birthday. Thanks for a great birthday present! I really do enjoy that!