Studying a meteor is akin to solving a mystery. The meteor leaves evidence through a crater, which is then investigated by scientists. Often, this evidence is difficult to analyze due to changes made by external forces, but Meteor Crater is one of the best-preserved impact craters on Earth. It is found in Arizona and was created 49 000 years ago by a meteor of approximately 45 meters in diameter (Whiteman et al., 2008). The meteor responsible for such a significant impact event was the Canyon Diablo Iron Meteorite, which is composed of 922 mg/g iron and 70.1 mg/g of nickel (Kenkmann, Hörz and Deutsch, 2005). The semi-arid environment in which this crater is located preserves past geologic activities and provides clues about historical environmental conditions. The current scarcity of vegetation of Meteor Crater and its physical traits also allow it to be a suitable analogue for craters present on Mars (Whiteman et al., 2008).
Before using Meteor Crater to solve mysteries of the past, it is vital to understand its composition. This crater is composed of sedimentary layers of Moenkopi siltstone, Kaibab limestone, and Coconino sandstone, found in horizontal strata from top to bottom (Whiteman et al., 2008). Moenkopi is comprised of calcium carbonate and siltstone, along with some quartz (Kenkmann, Hörz and Deutsch, 2005). Kaibab mainly consists of dolomite and some sandstone. Lastly, Coconino is pure sandstone (Kenkmann, Hörz and Deutsch, 2005). It is interesting to note that although carbonates and sandstones are indicative of marine environments, it is unusual to find finer grain sediments at the top rather than the bottom.
The meteor hit Arizona during a warm interval in the Wisconsin period of glaciation (Kring, 2017c). Pollen found in lake sediments in the area suggest the previous presence of woodlands near the crater, whereas current woodlands are found at higher elevations, as shown in Figure 1. The previous proximity of sagebrush, woodland, and pine forest suggested the presence of animals such as mammoths and mastodons near the crater. The pressure and wind speeds of 1000 km/h upon meteor collision would have caused the extinction of these animals (Kring, 2017c). Following the impact, the climate became arid and created multiple playa beds (Kring, 2017a). These beds are formed from short-lived lakes which evaporate and leave behind precipitation of evaporites, such as calcium carbonate.
Along with the history of Earth, Meteor Crater gives insight into the structure of Mars, as shown in Figure 2. Opportunity Rover explored Mars in 2004 to study Victoria Crater, for which Meteor Crater is an analogue regarding size and presence of gullies (Whiteman et al., 2008). These gullies are found primarily at the Kaibab layer of Meteor Crater and are thought to be due to precipitation (Kring, 2017d). Post-impact erosion had expanded the channels to the crater floor. By conducting radioactive dating of boulders in the levees, it was discovered that a total of 150 000 m3of water transported 500 000 m3of debris until the early Holocene, when the crater lake ceased to exist (Kring, 2017d). As such, information discovered from Meteor Crater can be used to understand characteristics of similar landforms on Mars.
Evidently, present conditions and residuals of geologic information on Meteor Crater are essential to progress in both the earth sciences and biological sciences. One can focus on the environmental conditions and interactions between flora and fauna or attempt to reconstruct previous surroundings on Mars to explore the possibility of life outside of Earth. After all, history can help with understanding the present and predicting the future.
References:
Kenkmann, T., Hörz, F. and Deutsch, A., 2005. Large Meteorite Impacts III. Geological Society of America.
Kring, D.A., 2017a. Barringer Meteorite Impact Crater. In: Guidebook to the Geology of Barringer Meteorite Crater, Arizona (a k a Meteor Crater)., Second. [online] Lunar and Planetary Institute, p.18. Available at: <https://www.lpi.usra.edu/publications/books/barringer_crater_guidebook/chapter_4.pdf>.
Kring, D.A., 2017b. Distribution of biotic communities in the area around Meteor Crater. [Map] Available at: <https://www.lpi.usra.edu/publications/books/barringer_crater_guidebook/chapter_13.pdf>.
Kring, D.A., 2017c. Environmental Effects of the Impact. In: Guidebook to the Geology of Barringer Meteorite Crater, Arizona (a k a Meteor Crater)., Second. [online] Lunar and Planetary Institute, p.6. Available at: <https://www.lpi.usra.edu/publications/books/barringer_crater_guidebook/chapter_13.pdf>.
Kring, D.A., 2017d. Post-impact Erosion and Sedimentation. In: Guidebook to the Geology of Barringer Meteorite Crater, Arizona (a k a Meteor Crater)., Second. [online] Lunar and Planetary Institute, p.14. Available at: <https://www.lpi.usra.edu/publications/books/barringer_crater_guidebook/chapter_15.pdf>.
Schmidt, L.J., 2018. In Search of Martian Craters | Earthdata. [Image] Available at: <https://earthdata.nasa.gov/user-resources/sensing-our-planet/in-search-of-martian-craters> [Accessed 15 Jan. 2019].
Whiteman, C.D., Muschinski, A., Zhong, S., Fritts, D., Hoch, S.W., Hahnenberger, M., Yao, W., Hohreiter, V., Behn, M., Cheon, Y., Clements, C.B., Horst, T.W., Brown, W.O.J. and Oncley, S.P., 2008. Metcrax 2006: Meteorological Experiments in Arizona’s Meteor Crater. Bulletin of the American Meteorological Society, 89(11), pp.1665–1680.