Helium-3
Primordial 3He on the is measured near hot spots and volcanos. Especially high 3He/4He ratios are measured in regions of high geothermal activity such as Yellowstone and Iceland.
Helium-3 is rare on Earth and sought-after for use in nuclear fusion research. More abundant helium-3 is thought to exist on the Moon.
Big Bang nucleosynthesis occurred within the first three minutes of the universe and is responsible for much of the abundance ratios of 1H (protium), 2H (deuterium), 3He (helium-3), and 4He (helium-4), in the universe .
It has two stable isotopes, helium-3 (two protons and one neutron) and helium-4 (two protons and two neutrons). The latter isotope is by far the more common; it is also the most stable and tightly bound of the light nuclei.
Because the near side is partly shielded from the solar wind by the Earth, the far side maria are expected to have the highest concentration of Helium-3 on the surface of the Moon.
The deuterium nucleus is bombarded by another proton, creating a helium-3 nucleus. The by-product of this is a photon in the form of a gamma ray (a very high-energy form of light).
For example, helium-3, with two protons and one neutron in each nucleus, and helium-4, with two protons and two neutrons, are two different isotopes of helium. For another example, see deuterium. [G97] ...
The number of deuterium nuclei that do not later undergo fusion reaction to make Helium-3 nuclei also depends sensitively on the temperature and density of the protons and neutrons.
Then a third proton is added to deuterium to form the light isotope of helium, helium-3. When two helium-3 nuclei collide, they form a nucleus of ordinary helium, helium-4 (two protons and two neutrons), and release two protons.
It has, for example, another stable isotope in addition to its two-neutron variety: helium-3, which has only one neutron and is produced in the reverse beta decay of hydrogen-3 (tritium).
Accelerating to one-tenth light speed using a deuterium/helium-3 nuclear fusion reaction to provide thrust, Daedalus was designed to put a sensor platform in orbit around Barnard's Star, ...
Other nuclei important in astronomy include: 2H, which has one proton and one neutron (the superscript 2 is the sum of the numbers of protons and neutrons); 3He (helium-3), two protons and one neutron; and 4He (helium-4), ...
In the second step a proton collides with the deuterium to produce a helium-3 nucleus and a gamma ray. In the third step two helium-3s collide to produce a normal helium-4 nucleus with the release of two protons.
This step begins as soon as deuterons appear. The reaction product is an isotope of helium"helium-3 (3He)"lacking one of the neutrons contained in the normal helium-4 nucleus. Energy is also emitted, again in the form of gamma-ray photons.
The space community talks hopefully about asteroid mining, about solar power satellites, and about Helium-3 mining on the Moon but, unfortunately, ...
One is that nucleosynthesis in an early hot universe correctly accounts for the cosmic abundance of the light nuclear isotopes such as hydrogen, deuterium, helium-3, helium-4, and lithium-7.
Tritium decays to helium-3 by emission of an electron ("beta emission") with a half-life of 12.3 years. Tritium can be synthesized from deuterium via neutron bombardment, or by fissioning lithium (see lithium).
 See also: Helium, Hydrogen, Light, Time, Energy
  
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