Unique volcanic domes of Gruithuisen
Unlike most volcanic features on the Moon, they are silicic, not basaltic.
Seen here are two volcanic domes which are unlike most other volcanic places on the Moon.
Until a couple of billion years ago, the Moon was a volcanically active place, the solidified lava plains of Maria (plural for Mare) being the most prominent sign. Most of this volcanism was basaltic in nature, but today's featured image is different. Stretching about 20 km across each, these domes are formed of different kind of volcanic material, and we know that from observations of these domes via Earth-based telescopes and past lunar orbiters, specifically Lunar Prospector and Clementine.
Recent data from the Diviner instrument on NASA's Lunar Reconnaissance Orbiter (LRO) confirmed that the volcanic magma that formed these domes were silicic in their composition instead of basaltic.
What are the mechanisms that create such types of volcanic domes rich in silica on the Moon? We don’t know! Due to their unique nature, they are a high-priority target for future lunar exploration.