Top 10 Features on Mercury’s Surface (Craters, Scarps, Basins)

#1: Caloris Basin (Diameter ~950 miles)

The Caloris Basin is not just the largest impact structure on Mercury—it’s one of the largest in the entire solar system. Stretching nearly 950 miles in diameter, this colossal basin was formed over 3.8 billion years ago when a massive asteroid slammed into Mercury’s surface. The resulting impact was so powerful that it created rings of mountainous terrain, uplifted plains, and shockwaves that traveled through the planet’s interior and fractured the crust on the opposite side. This “weird terrain,” as scientists nicknamed it, is one of the most unusual features in planetary geology. When Mariner 10 photographed part of Caloris in the 1970s, scientists were stunned by its scale. But it wasn’t until the MESSENGER mission decades later that the full basin was revealed, including the inner plains flooded by ancient lava flows. The floor of Caloris is marked by a chaotic mix of ridges, fractures, and smooth plains, suggesting complex resurfacing over time. It’s not just a scar—it’s a chronicle of planetary trauma and rebirth.

#2: Discovery Rupes (Length ~370 miles; height ~1 mile)

Discovery Rupes is one of Mercury’s most dramatic cliff-like formations, known as a lobate scarp. These scarps are steep, curved faults where one side of the crust has pushed up over the other. Discovery Rupes stretches roughly 370 miles in length and towers about a mile high. It’s believed to have formed as Mercury’s core cooled and the planet contracted—essentially shrinking like a raisin as it aged. These enormous “wrinkles” are evidence of planetary shrinkage, a process still not fully understood. What makes Discovery Rupes particularly fascinating is that it cuts through craters, meaning it formed after them and is relatively young in geological terms. The fact that Mercury is still deforming this way today suggests it may not be as geologically dead as once thought. This feature serves as a vivid reminder that even in silence, planets can move.

#3: Beethoven Basin (Diameter ~410 miles)

Named after the composer Ludwig van Beethoven, this impact basin spans over 400 miles in diameter and stands as one of the most well-preserved large basins on Mercury. Though not as immediately eye-catching as Caloris, Beethoven Basin offers an incredibly detailed look at how impacts shape planetary crusts. Its flat floor and subdued rim suggest that volcanic or tectonic activity may have partially resurfaced it. MESSENGER’s detailed topographic maps revealed ghost craters—ancient impacts nearly buried by lava—which provide a timeline for the basin’s complex geological history. The basin is also surrounded by secondary craters and ejecta rays, a testament to the power of its formation. Though named for an Earth-bound musical genius, Beethoven Basin’s enduring legacy lies in its ability to reveal Mercury’s early bombardment history.

#4: Great Valley (Length ~620 miles; width ~250 miles)

The Great Valley on Mercury is a vast, linear depression unlike anything seen elsewhere in the solar system. Measuring about 620 miles long and 250 miles wide, this feature is believed to be a massive tectonic trough formed as the crust collapsed and slid downward. It’s bounded by parallel fault scarps, giving it the appearance of a rift valley—but Mercury doesn’t have plate tectonics like Earth. Instead, scientists believe this was formed by cooling and contraction of the planet’s interior, making it a compelling piece of the planetary shrinkage puzzle. Its sheer size dwarfs similar features on other rocky worlds and raises questions about how tectonic activity operated early in Mercury’s history. The valley’s smooth floor also suggests it was resurfaced by lava or dust flows, making it a true geologic hybrid of volcanic and tectonic processes.

#5: Raditladi Basin (Diameter ~180 miles)

The Raditladi Basin stands out on Mercury for its relative youth and pristine preservation. Spanning about 180 miles, this impact structure is surrounded by a distinct ring of concentric fractures and filled with smooth plains that may be volcanic in origin. Raditladi is estimated to be less than a billion years old, making it one of the youngest large basins on the planet. This makes it a geological time capsule for studying Mercury’s later evolutionary stages. Unlike older basins that have been weathered and overprinted by subsequent impacts, Raditladi retains crisp edges and subtle surface features. The basin also shows signs of hollows—bright, shallow depressions thought to form from the loss of volatile materials—making it a convergence point for multiple unexplained surface processes.

#6: Rembrandt Basin (Diameter ~445 miles)

Second in size only to Caloris, the Rembrandt Basin spans about 445 miles and features a mix of ancient and relatively young surface formations. Discovered during MESSENGER’s flybys, the basin surprised scientists with its well-preserved rings, interior wrinkle ridges, and evidence of tectonic faulting. One particularly striking feature is a giant scarp that cuts across the basin floor, indicating that tectonic activity occurred after the impact event. This tells scientists that Mercury’s interior remained active long after its outer shell cooled. The Rembrandt Basin is a geological palimpsest—a record overwritten again and again with new activity, yet still preserving traces of its origin. It’s also one of the only basins where researchers can study the direct relationship between basin formation and global tectonics.

#7: Suisei Planitia (Size ~300,000 square miles)

Suisei Planitia, or “Mercury’s Plains of Comets,” is a vast smooth area likely formed by lava flows and impact melt from the Caloris event. Covering more than 300,000 square miles—larger than the state of Texas—this region is one of the most expansive examples of volcanic resurfacing on Mercury. Suisei is filled with ghost craters and shallow depressions that suggest it was once bombarded heavily before being buried by molten material. It acts like a geologic sponge, absorbing layers of history and preserving impact records beneath its surface. The planitia’s relatively flat terrain may also hold clues about Mercury’s early volcanic activity and how the planet handled internal pressure release following catastrophic impacts.

#8: Kuiper Crater (Diameter ~40 miles)

Though small compared to Mercury’s giant basins, Kuiper Crater is one of the brightest and youngest impact craters on the planet. Measuring around 40 miles in diameter, it features a sharply defined rim and an intensely reflective ejecta blanket, indicating a relatively recent origin. Kuiper Crater offers a pristine example of a “fresh” crater—its rays still span hundreds of miles, undisturbed by space weathering or subsequent impacts. Named after astronomer Gerard Kuiper, the crater is often used as a reference point for analyzing other impact sites on Mercury. Its central peak and impact melt features make it a textbook example of primary cratering processes. Kuiper gives scientists a real-time look into what Mercury’s surface looked like billions of years ago, before the scars had time to fade.

#9: Carnegie Rupes (Length ~250 miles)

Carnegie Rupes is another one of Mercury’s most prominent lobate scarps, stretching about 250 miles and rising several thousand feet above the surrounding terrain. It likely formed as the crust compressed during planetary cooling, similar to Discovery Rupes. What makes Carnegie particularly significant is its placement across multiple ancient craters, indicating its younger geological age. Carnegie has a sweeping, curved profile that adds to its visual drama, and its study has helped scientists estimate how much Mercury’s diameter has shrunk—up to 7 miles over the last few billion years. These scarps are not only geological features but also dynamic tools for measuring planetary change.

#10: Hokusai Crater (Diameter ~60 miles)

Hokusai Crater is a showstopper on Mercury, famous for its enormous ray system that stretches thousands of miles across the planet. Named after the Japanese artist Katsushika Hokusai, this 60-mile-wide crater is young, bright, and photogenic. The crater’s rays are so extensive that they were mistaken for surface grooves before MESSENGER provided high-resolution images. Hokusai is particularly useful for studying Mercury’s impact chronology. Its well-defined ejecta pattern suggests the impactor struck at high velocity and released significant energy—enough to blanket nearby regions in fresh material. It’s also one of the best examples of how Mercury’s lack of atmosphere preserves geological events that would otherwise erode or fade on other planets.

The Story Etched in Stone

From giant impact basins that tell of ancient cataclysms to mysterious scarps formed by planetary contraction, Mercury’s surface features offer a glimpse into a world frozen in deep time. Unlike Earth, where erosion and weather constantly reshape the land, Mercury preserves its past in stone. Each crater, basin, and fault line is a geological relic—a page in the story of how rocky planets evolve. As spacecraft like BepiColombo prepare for future exploration, these features will guide scientists toward new discoveries and may even reveal more about the forces that shaped not only Mercury, but Earth and other terrestrial planets as well.