1. Why does the article mention the Grand Canyon?
The article compares the Grand Canyon to Vallis Schrödinger and Vallis Planck, two craters located near the moon’s south pole. These moon craters are deeper than the Grand Canyon—but were created far more quickly.
(RI.4.8 Reasons and Evidence)
2. How has scientists’ understanding of the moon’s dark spots changed over time?
Scientists used to believe that the dark spots on the moon were bodies of water. Now scientists know that these spots were caused by asteroid strikes more than 3 billion years ago. They were later filled with lava that eventually froze.
(RI.4.5 Comparison)
3. How has the Lunar Reconnaissance Orbiter helped scientists learn about the moon?
The Lunar Reconnaissance Orbiter has shown that Vallis Schrödinger and Vallis Planck were created by an asteroid crash. This spacecraft has also mapped and taken photos of the moon.
(RI.4.2 Main Idea and Key Details)