Black moon years. When February is without full moon, then the preceding January or December and the following March or April have two full moons. As with the case of two new moons in a month, whether a black moon by this definition occurs depends on the time zone. Calculated in UTC, instances of a month without full moon between 1990 and 2040 are: Another use of the term is for the absence of the new moon in a calendar month. This can occur only in February; it happens about every 19 years. When February is without new moon, then the preceding
Colonization of the Moon hot for an extended period of time. (This allows the molecular structure to realign.) Exporting material to Earth in trade from the Moon is more problematic due to the cost of transportation, which would vary greatly if the Moon is industrially developed (see "Launch costs" above). One suggested trade commodity is helium-3 (He) which is carried by the solar wind and accumulated on the Moon's surface over billions of years, but occurs only rarely on Earth. Helium-3 might be present in the lunar regolith in quantities of 0.01 ppm to 0.05 ppm (depending on soil). In 2006 it had a