NASA's twin satellites were successfully launched in early September to map the Moon's gravitational field and internal structure. The Delta-II rocket carrying the space probes lifted from Cape Canaveral on the 10th of September, after a two-day delay. This was the last start of the legendary launch vehicle from the East Coast and most likely the penultimate overall. The Delta-II lifted a lot of GPS and Iiridum birds and numerous scientific satellites, space probes and telescopes, including all American Mars probes since the nineties. Only a single one of its 146 launches was a complete failure although that one produced very spectacular fireworks.

Our Moon formed about 4.5 billion years ago when the proto-Earth was blasted by another, somewhat smaller but quite large protoplanet. The excavated material that remained in orbit around the Earth then coalesced into the Moon. The time of the formation can be quite reasonably determined through the dating of the oldest rocks that came into existence. As the material of the Moon cooled down, lighter minerals floated to the top and formed a solid crust, creating the rocks that tell the story of the first times. According to calculations, the upper layers solidified in only a thousand years, creating a lid that slowed down the cooling of the lower layers dramatically to ten million years. Though events like massive impacts and volcanism may've altered the age of the surface materials here and there, almost all of the oldest rocks formed during these mere ten million years. Or did they?

Rock sample 60025, collected by the crew of Apollo 16, while still on the Moon.

Our Moon sports a few oddities. One of them is the remarkable difference between the properties of the hemispheres facing toward and away from us: on this side the crust is thinner and smoother, displaying basins filled with dark basalt while the other side is more thick, a heavily cratered highland. The abundance of some elements (KREEP: potassium, rare-earth elements and phosphorus) is also different. There have been theories to explain this dichotomy already, like differences in tidal heating or the impact that formed the South Pole-Aitken Basin. A new theory is based on an impact, but instead of a stranger from far, it assumes an event between moon siblings.

One quick look at Evadot's brilliant GLXP scoreboard will tell you that some teams are way ahead in develompent, funding and business connections than others. (Its also worth noting that Puli barks in the middle of field despite entering the competition in the last days!) New York Times asked the three leading teams, and we sample the report here.

The THEMIS (Time History of Events and Macroscale Interactions during Substorms) satellites of NASA were launched in 2007 to investigate the magnetosphere of our planet. The five probes orbited at different distances from the Earth, P1 and P2 being the two farthest. The program was greatly successful, providing new discoveries about the dynamics of the magnetosphere, but by 2009 the future of P1 and P2 looked more and more grim. They passed through he Earth's shadow regularly, relying on their batteries as designed. However, as their orbit gradually changed, they spent more and more time in darkness and it was uncertain how long would they last. But then a solution emerged: the two, fully functioning satellites with ample supply of fuel will be transferred to the Moon.

Original orbits of the five THEMIS satellites. The two farthest were transferred to the Moon.