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The expansive canyons known as Vallis Schrödinger and Vallis Planck offer a striking glimpse into the dynamic forces that have shaped the Moon’s surface over billions of years.
Vallis Schrödinger (to the left) and Vallis Planck (to the right) represent colossal depressions formed from the debris of the impact that created the Schrödinger Basin, situated in the Moon’s southern hemisphere. Credit: NASA/SVS/Ernie T. Wright
Every year, millions flock to the Grand Canyon, a geological wonder formed by the gradual erosion of rock by the Colorado River over millions of years. Spanning up to 18 miles (29 kilometers) in width and plunging more than a mile (1,857 meters) deep, it stands as a testament to the slow yet powerful forces of nature. The sedimentary layers tell a story of time, showcasing the relentless power of water as it carves through the landscape.
In stark contrast, the vast gouges of Vallis Schrödinger and Vallis Planck were created in an astonishingly brief moment—about 10 minutes. These magnificent valleys radiated from the northern border of Schrödinger Basin, which was formed during a cataclysmic impact from an asteroid roughly the size of Manhattan, striking the Moon’s far side nearly 4 billion years ago.
A recent study published on February 3 in Nature Communications delves into the formation of these features, likening them to lunar grand canyons. The study, led by planetary scientists David Kring of the Lunar and Planetary Institute and colleagues Danielle Kallenborn and Gareth Collins of Imperial College London, combines scientific analysis with an engaging exploration of this geological drama.
A Violent Origin Story
Due to its position on the Moon’s southern far side, Schrödinger Basin and its accompanying canyons remain largely hidden from view from Earth. However, this area is gaining increasing attention, located just 190 miles (300 km) from the lunar south pole and within the southern rim of the 1,500-mile-wide (2,400-kilometer) South Pole-Aitken Basin, which is the Moon’s oldest and largest impact crater. It also lies near the Artemis Exploration Zone, where NASA aims to land astronauts beginning with the Artemis 3 mission. Excitingly, a robotic lander, funded by NASA and developed by Draper Laboratory, is set to explore Schrödinger in the coming year.
Kring and his team investigate the immense forces responsible for forming Vallis Schrödinger and Vallis Planck. While the Grand Canyon’s creation unfolded over eons, the lunar counterparts materialized in a fraction of that time. Through the analysis of 15 secondary craters found within Vallis Schrödinger—using data gathered by NASA’s Lunar Reconnaissance Orbiter—researchers unraveled the dynamics of this explosive period.
Despite being referred to as a “valley,” Vallis Schrödinger technically qualifies as a catena, a linear sequence of craters created by multiple impacts from the same source—a stream of projectiles propelled into space by the colossal force that formed Schrödinger Basin.
Typically, secondary craters resulting from a primary impact under 160 miles (260 km) wide are about 4 percent of the primary’s width. When applying this ratio to the 320 kilometers of the Schrödinger Basin, it becomes clear that the 15 secondary craters are relatively oversized. This may be due to the area already being weakened by an earlier impact from the South Pole-Aitken Basin, occurring roughly 500 million years prior. Nonetheless, the orientation and location of both Vallis Schrödinger and Vallis Planck unmistakably indicate their genesis from the Schrödinger Basin impact.
Vallis Schrödinger extends 168 miles (270 km) northwest from the basin and measures up to 12 miles (20 km) across, while Vallis Planck stretches 174 miles (280 km) northward and reaches widths of up to 17 miles (27 km). The Schrödinger Basin itself spans 200 miles (320 km) and is characterized by a distinct 93-mile-wide (150 km) ring peak at its center, surrounded by a floor marked by basalt features produced by previous volcanic activity. Credit: NASA/SVS/Ernie T. Wright
By examining the projectile dynamics from the Schrödinger Basin impact, researchers estimated the timeframe for the formation of these lunar grand canyons. The necessary velocities to project 0.3- to 0.8-mile-wide (0.5- to 1.25 km) ejecta that formed Vallis Schrödinger ranged between 0.6 miles per second (1 km/s), with Vallis Planck’s farther reaches requiring speeds of around 1.23 to 1.28 km/s. These findings suggest that the primary impacts responsible for creating the canyons occurred within a window of 10 minutes, with flight times for the ejecta ranging from about 4.5 to 15 minutes in the case of Vallis Schrödinger, and slightly longer for Vallis Planck.
Even more astonishing is that the force exerted during the impacts that formed Vallis Schrödinger was approximately 700 times greater than the collective yield of all nuclear tests conducted by the U.S., Russia, and China, or equivalently, 130 times the global nuclear arsenal’s power.
Implications for Artemis
The location of Schrödinger Basin near the Moon’s south pole is significant not just for its geological importance but also for the upcoming science missions planned under NASA’s Artemis program. The Artemis landing zones are situated within the splash range of ejecta from the Schrödinger impact, meaning that important samples from the South Pole-Aitken Basin could be obscured by material ejected during that event. One goal of the Artemis missions is to retrieve samples that may provide insights from depths reaching up to 62 miles (100 km) beneath the lunar surface. Fortunately, the analysis of Vallis Schrödinger, Vallis Planck, and surrounding ejecta patterns suggests that the debris distribution is asymmetrical, with relatively less material landing in the Artemis Exploration Zone.
The formation of these lunar grand canyons is not only a fascinating subject of study but also underscores the complexities of our natural satellite’s history and evolution. As lunar exploration continues in the coming years, more discoveries will enhance our understanding of the Moon and its geological past, marking an exciting era in lunar research.
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