Geologic Age of the Apollo 17 Landing Site

Dayana Chavez, Katarina Dominguez, Christina Riou, Jacob Zamarripa, Jorge Zertuche, and Carlos Vasquez 4200 Jackson Keller, San Antonio, TX 78213

Abstract: Results: 7 6 8 The moon, unlike the Earth, is a relatively inactive body. This property allows scientists to study the evolution and age of the moon in a different way than Earth. Relative and radiogenic ages of features We listed the 20 samples by age on a timeline (Fig. 3) and plotted their approximate locations on the on the moon aid lunar scientists to better understand how the lunar surface evolved. Brief visits to the Apollo 17 traverse map to show their relationship to the different geologic features (Figs. 4,5,6). 9 Moon by Apollo astronauts, between 1969-1972, provide samples from known locations on the lunar Radiogenic Dating states that the samples collected around the Apollo 17 traverse range from 4 surface. Apollo 17 is the most appropriate site to research due to its large number of samples and use 3.6-4.2 billion years 5 of the most advanced age dating techniques on the samples. Crater counting and radiogenic dating Age: 3.80 ± 0.003 Billion Years Crater Counting though, states that the surface age should only be around 4 billion years old. 3 methods were used to identify the ages of basalt and other samples collected along the Apollo 17 Lithology: High-Ti mare basalt 1 traverses. A map and timeline were created to illustrate the distribution and chronology of the sample Weight: 2957 grams ages; 20 samples were used, nine of which were composed of basalt. We found that most samples Location: Central Valley, near the were between 3.7 and 4.1 billion years old. The samples collected on the maria have younger Apollo 17 lunar module radiogenic ages than highlands and other features, in addition to a smaller crater density. From this we 2 Scale- 1:25,000 Kilometers Fig. 6 infer that the maria are relatively younger than the highlands and other features. Information from both satellite images and samples allow scientists to investigate how the moon evolves over time, as well as the general geologic make-up of the moon. Future studies include an in depth look at all the samples collected from the moon, as well as scanning the moon to choose the next appropriate landing site for a mission back to the moon. Northern Image: •Crater Count >2 ~ 150 •Surface Area ~ 9 km2 •Crater Density ~ 16,666,666.67 Central Image: Introduction: •Crater Count ~ 160 •Surface Area ~ 7 km2 Lunar characteristics were first research in order for a more complete understanding of the surface of •Crater Density ~ 22,857,142.8571 the moon. The origin theories were studied, and it was found that most of the team agrees with the Age Impact Theory, which states that the moon was formed by the debris of a meteor impact when the Western Image (yellow): earth was still molten. It is also believed that maria were formed by rivers of lava, which would •Crater Count ~ 130 create a younger outer surface compared the highlands, which cooled after the impact, and are thus Fig. 3 •Surface Area ~ 15 km2 older. •Crater Density ~ 8,666,666.67 Apollo 17 was the mission selected for study for two main reasons: 1) the landing site was near two maria, which would allow for study a study of the two, and 2) the technology used during and after 7 6 this mission are the most beneficial to our study. Being the only Apollo mission with a scientist on the 8 moon, the samples collected are of good quality and marked in the correct location along the traverse Fig. 7 route. In addition, radiogenic dating was used to find the ages of the samples which was a method of dating we wanted to incorporate into our study.

9 Based on our crater counting ages, the data from radiogenic dating appears to contradict our results by placing the youngest samples in the most heavily cratered area; in theory, surfaces that have more impacts tend to be older. Also, while the radiogenic dates have a wide age range between 3.6-4.2 billion years, our crater counting calculates the Apollo 17 landing site to be around 4 billion years old. 4

5 Methods: 3 Radiogenic Dating 1 This is a technique in which samples collected are tested for radioactive ions. Ions have a set amount Conclusions: of time to stabilize and by comparing the rate of decay of these ions from that which are present in the samples, a near precise age for these samples can be determined. Among the best-known methods are Our data shows that the samples collected on the mare surface at the Apollo 17 site cover an age Potassium-Argon (K-Ar) and Uranium-Lead (U-Pb) (Fig. 1). range of 0.6 billion years. This wide range can be explained through two known factors: 1) While samples were collected primarily on the mare surface, they represent different geologic features and Scale- 1:25,000 Kilometers 2 rock types formed at different times and 2) Another factor to consider is that most of the craters Oldest 4 Billion years 3.9 Billion years 3.8 Billion years 3.7 Billion Years Youngest counted in the images of the traverse could be secondary craters instead of primary impact craters. Though the graph used accounts for that, this may explain why the crater count age found was higher Fig. 4 than the radiogenic age. The data from the two age dating methods shows that the lava flows at the Crater Counting Fig. 1 Apollo 17 landing site are approximately 3.8 billion years old. This method is less precise, but provides an age for a given area on the surface based on observations 6 7 from images (Fig. 2). This leaves more room for human error, but is still useful for finding the 8 relative ages. This method involves calculating the area of the image, counting the craters while grouping them based on their diameter, and then finding each group’s crater density per 1,000,000 9 BOTTOM km2. A logarithmic graph is used so that when the points are plotted the relative ages of the surfaces TOP in the image can be determined. Acknowledgements: To find the crater density this equation was used: 4 Crater density = Number of Craters * 1,000,000 [km2]/image size [km2] 5 Age: 3.30 +- 0.04 Billion Years NASA 3 Exposure Age: 575 +- Million Years Lunar and Planetary Institute 1 Lithology: Olive Basalt Breccia with a Glassy The Smithsonian Institution Matrix Dr. Garry Size: 240 cm^3 Weight: 318 grams Mr. Shaner Scale- 1:25,000 Location: Southeast rim of Van Ser Crater Mr. Henry 2 Kilometers Mrs. McCool Fig. 5 Fig. 2