New images from NASA’s Lunar Reconnaissance Orbiter Camera show fascinating cracks, known as grabens, surrounding an ancient lunar sea on the Moon’s near side. These grabens highlight how a large section of the Moon’s crust has been pulled apart over time.
How Did This Happen?
According to Thomas Watters, a planetary scientist at the Smithsonian’s National Air and Space Museum, the area known as Mare Humorum is a key player in this story. It’s filled with dense basalt from ancient volcanic activity. This basalt forms a heavy layer that stretches the crust underneath, causing it to sag and crack.
During the Imbrian period—an era marked by intense volcanic activity—Mare Humorum was flooded with lava for millions of years. As this lava cooled, it created several valleys that can now be seen from space.
What Are Grabens?
Grabens are elongated valleys formed when a section of the crust drops between two faults. Recent studies indicate that these features are enormous, spanning hundreds of kilometers across the Moon’s surface. A dedicated mapping effort revealed over 1,800 graben segments on the near side alone.
Most of these grabens date back about 3.7 to 3.4 billion years, with many forming during a peak period of geological activity. Interestingly, some younger grabens have appeared as recently as 50 million years ago, suggesting that changes in the Moon’s crust are still happening.
The Broken Ring Around Mare Humorum
On the eastern edge of Mare Humorum lies a system of valleys known as Rimae Hippalus. These valleys form a broken ring over 150 miles long. Each segment of this ring shows how the crust has reacted to the underlying weight of settled lava.
The innermost valley remains relatively undisturbed, while others show signs of being filled in by later lava flows.
The Moon’s Ongoing Changes
Watters suggests that the Moon is gradually contracting due to cooling, but this doesn’t tell the whole story. The grabens indicate that some areas are still stretching, showing a complex interplay of forces on the lunar surface.
These findings help researchers understand where to safely land spacecraft in the future. Regions with fresh grabens could contain hidden risks.
By carefully mapping these geological features, scientists can better interpret the Moon’s history, linking ancient structures to the more recent dynamics at play.
In summary, the study of these grabens not only reveals the history of our Moon but also offers valuable insights for future exploration endeavors. The lunar surface continues to change, providing a deeper understanding of geological processes on both the Moon and Earth.
For more detailed information, visit NASA’s Lunar Reconnaissance Orbiter.
