10:45 AM - 11:00 AM
[SCG48-01] The Latest Views of Lunar and Martian Internal Structures: Implications From the Apollo and InSight Seismic Observations
★Invited Papers
Keywords:Planetary internal structure, Moon, Mars, Planetary seismology
The internal structure of a planetary body possesses an essential piece of information to trace back its past evolution processes. For example, the geological activities of the Moon and Mars are by far inactive (or almost stopped) compared to those of our planet, and the ancient memories have been preserved even today due to weak erosions on these bodies.
There are several approaches to probing a planetary interior, such as radar sounding, gravity field observation, heat flow measurement, electromagnetic field observation, and seismic observation. Among these, seismic observation allows us to illuminate the planetary interior on various spatial scales depending on the target frequency and provide clear views of not only 1-D but also 3-D structural variations inside, helping us illustrate the internal dynamics.
The first seismic observation outside our planet was performed in the Apollo missions (11, 12, 14, 15, 16, and 17) on the Moon, where a seismic network was constructed on the near side. The 8 years of observations brought us more than 33,000 seismic events (e.g., meteorite impacts, tidally driven quakes, tectonic quakes), enabling us to access the lunar interior. Recently, NASA’s InSight mission (2018-2022) successfully performed seismic observation on Mars. Although InSight conducted seismic monitoring at a single station, its broadband and sensitive seismometer was sufficient to capture marsquakes and obtain the internal structure.
Even though these planetary seismic data splendidly improved our understanding of the lunar and Martian internal structure, it is considered that further explorations are necessary to illustrate better the past/present dynamics of a planetary interior (e.g., the time scale of the mantle overturn, dynamo process, heterogeneous internal evolution). However, the currently available datasets are insufficient to give us clear views of some paramount factors, such as the stratification in the mantle, core property, and three-dimensional structure. For this reason, some countries are planning to conduct seismic observations (especially on the Moon) to obtain higher-quality data than those available today.
In the presentation, we will review the internal structure models of the Moon and Mars obtained through the analysis of the Apollo and InSight seismic data and also introduce some seismic exploration missions planned in the late 2020s.
There are several approaches to probing a planetary interior, such as radar sounding, gravity field observation, heat flow measurement, electromagnetic field observation, and seismic observation. Among these, seismic observation allows us to illuminate the planetary interior on various spatial scales depending on the target frequency and provide clear views of not only 1-D but also 3-D structural variations inside, helping us illustrate the internal dynamics.
The first seismic observation outside our planet was performed in the Apollo missions (11, 12, 14, 15, 16, and 17) on the Moon, where a seismic network was constructed on the near side. The 8 years of observations brought us more than 33,000 seismic events (e.g., meteorite impacts, tidally driven quakes, tectonic quakes), enabling us to access the lunar interior. Recently, NASA’s InSight mission (2018-2022) successfully performed seismic observation on Mars. Although InSight conducted seismic monitoring at a single station, its broadband and sensitive seismometer was sufficient to capture marsquakes and obtain the internal structure.
Even though these planetary seismic data splendidly improved our understanding of the lunar and Martian internal structure, it is considered that further explorations are necessary to illustrate better the past/present dynamics of a planetary interior (e.g., the time scale of the mantle overturn, dynamo process, heterogeneous internal evolution). However, the currently available datasets are insufficient to give us clear views of some paramount factors, such as the stratification in the mantle, core property, and three-dimensional structure. For this reason, some countries are planning to conduct seismic observations (especially on the Moon) to obtain higher-quality data than those available today.
In the presentation, we will review the internal structure models of the Moon and Mars obtained through the analysis of the Apollo and InSight seismic data and also introduce some seismic exploration missions planned in the late 2020s.