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Well we don't yet have the actual proof that there's an abundance of 3 He ( Helium-3) embedded in the Lunar regolith that would make any mining worth our trouble. All we have so far is the indication that there might be, as shown by the trace amounts of 3 He detected in the regolith samples extracted by the Apollo missions. Current estimates are that there might be anything from 1 ppm up to 50 ppm (parts per million) of 3 He embedded in the Lunar regolith, and while that might not seem much, if true, it might make any exploitation of it feasible. Of course, the higher ppm, the better. I have to add here that Apollo sampling of Lunar regolith arguably isn't the most indicative of levels of 3 He embedded in it, since much of the surface trapped 3 He would likely escape due to mechanical disturbance and electrostatic discharge when Apollo missions sampled it by drilling. But it is a better representative of how much of 3 He is contained within the topmost Lunar bedrock, with Apollo 11 having best success landing in the Ti O2 ( Titanium Dioxide) rich region of Mare Tranquillitatis. Surfaces with electro-conductive metallic minerals seem to be the best, 3 He rich (1) candidate regions suitable for Lunar surface mining on top of permanently shadowed Lunar polar regions (2). What makes this rare isotope so tempting is the energy stored in it as two of 3 He atoms coupled in a superheated plasma break apart into two protons and a 4 He ( Helium-4) alpha particle: $\require mhchem \ce ^3_2 He + ^3_2 He \to ^4_2 He + 2\!^1_1p^+ + \text 12.86 Me V $ This is the energy density in mega electronvolts per mole (3 grams) of 3 He plasma that was reached by the third-generation Helium-3 fusion reactor, developed by Gerald Kulcinski at the University of Wisconsin. This is a reaction that produces very high amounts of energy, and at the same time very little harmful byproduct. Second-generation fusion.
i Here is a pop quiz: How many trees are on the planet? Most people have no idea. A new study says the answer is more than 3 trillion trees — that's trillion with a T, and that number is about eight times more than a previous estimate. Thomas Crowther was inspired to do this tree census a couple of years ago, when he was working at the Yale School of Forestry and Environmental Studies. He had a friend who was working with a group with an ambitious goal: trying to fight global warming by planting a billion trees. A billion trees sounded like a lot. But was it really? They didn't know if planting a billion trees was going to add 1 percent of the world's trees, add 50 percent of the world's trees, recalls Crowther. They didn't even know if it was even possible to fit a billion trees on Earth. So his pal asked him a simple question: How many trees are growing on our planet? I assumed that this was somewhere out there, it's information that someone will know, says Crowther. That turned out to be wrong, he says. Having spoken to a lot of forestry experts, it doesn't seem like anyone had any idea. There was one estimate based on satellite images: about 400 billion trees worldwide, or 61 trees for every person. But there were doubts about that number because another recent estimate, based on ground-truthed measurements, found 390 billion trees in the Amazon basin alone. i Crowther knew there was a way to get much better numbers. We used ground-sourced information, says Crowther. All of the information that went into our models was generated from people standing on the ground counting numbers of trees in a given area. And so we could relate this information to what the satellites are telling us. To get a better estimate, his team took advantage of the fact that countries produce detailed forest inventories. It definitely couldn't have been done without all of those huge.