Solving the Puzzles of the Moon
Shun Karato, Yale University
After 50 years from the first landing of men on the Moon, about 380 kg of samples were collected by the Apollo mission. Chemical analyses of these samples together with a theory of planetary formation led to a “giant impact” paradigm (in mid 1970s). In this paradigm, the Moon was formed in the later stage of Earth formation (not the very late stage, though), when the proto-Earth was hit by an impactor with a modest size (~ Mars size) at an oblique angle. Such an impact is a natural consequence of planetary formation from a proto-planetary nebula. This collision may have kicked out mantle materials from the proto-Earth to form the Moon. This model explains mostly rocky composition of the Moon and the large angular momentum of the Earth-Moon system. High temperatures caused by an impact likely removed much of the volatile components such as water.
However, two recent geochemical observations cast doubt about the validity of such a paradigm. They include (i) not-so-dry Moon suggested from the analysis of basaltic inclusions in olivine, and (ii) the high degree of similarities in many isotopes. The first observation is obviously counter-intuitive, but the second one is also hard to reconcile with the standard model of a giant impact, because many models show that a giant impact produces the Moon mostly from the impactor. In this presentation, I will show how one can solve these puzzles by a combination of physics/chemistry of materials with some basic physics of a giant impact.
The NMSU Department of Astronomy will host a virtual online open house from the Tortugas (A) Mountain Observatory Monday, Dec. 21. This will coincide with a rare conjunction of Jupiter and Saturn, an event when the two planets will be as close together in the sky as they have been for hundreds of years. The virtual event will be held via Zoom videoconferencing and will include a short virtual tour of the recently refurbished Tortugas Mountain Observatory, followed by some remote imaging of Jupiter and Saturn, weather permitting, as well as a short presentation about connection with research on these gas giant planets.
The online event will start at 4:30 p.m. and last until around 6 p.m. Participants will need to download Zoom before joining.
Zoom link: https://nmsu.zoom.us/j/94370800438
However, a password will be required to join the meeting. To receive the password, email firstname.lastname@example.org and we will send you the password before the event. For more information, contact Jon Holtzman at 575-646-4438.