APOD: 2023 January 16 – Moon Enhanced

Good morning, Rallypoint, and welcome to the January 16th edition of Astronomy Picture of the Day (APOD): "Moon Enhanced." Detailed surfaces are always interesting, and this image of our Moon takes it to another level. From the impact craters, it is apparent that the Moon has been under more or less constant bombardment since it was formed some 4-6 billion years ago. The clear areas (called maria, or Seas) were once lakes of molten lava. The colors we see, however, are not visibly present. They are enhanced based on what we've learned about lunar composition. The blue areas indicate concentrations of iron, and the orange indicate concentrations of aluminum. The presence of iron is consistent with theories that suggest past molten lava. Where did the aluminum come from?

Before you think a supernova, a simpler explanation is worth considering. The pertinent radioactive isotope is aluminum-26. Researchers propose that aluminum-26 formed close to the young sun in the inner part of its surrounding planet-forming disk. As material fell from the disk's inner edge onto the sun, it created shockwaves that produced high-energy protons known as cosmic rays. This energy then slams the surrounding disk, colliding with the isotopes aluminum-27 and silicon-28, changing them into aluminum-26.

Since it has a short half-life (about 770,000 years), aluminum-26 must have been formed or mixed into the young sun's surrounding planet-forming disk shortly before the condensation of the first solid matter in our solar system. It can provide enough heat through radioactive decay to produce planetary bodies with layered interiors: like our Earth. And the Moon. The heat from radioactive decay also helps to dry out early planetesimals to produce water-poor, rocky planets.

The hand of a Creator at work? Hmmm.