Thickness of Lava Flows Within the Northern Smooth Plains on Mercury as Estimated by Partially Buried Craters

• Published in: Geophysical research letters 2020-10, Vol.47 (20), p.n/a
• Main Authors: Du, Jun, Wieczorek, Mark A., Fa, Wenzhe
• Format: Article
• Language: English
• Subjects: Ascent; Bombardment; crater degradation; crater morphometry; Data acquisition; Degradation; Earth Sciences; Ejecta; Elevation; Image acquisition; Imagery; Lava; lava flow thickness; Lava flows; Lunar craters; Lunar surface; Magma; Mercury; Mercury (planet); Mercury surface; Mercury's craters; MESSENGER Mission; Moon; northern smooth plains; partially buried craters; Planetology; Profiles; Sciences of the Universe; Thickness; Topography
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL090578

Partially and completely buried impact craters are widely distributed over the northern smooth plains of Mercury. Using imagery data acquired from the MESSENGER mission, we compiled a database of 257 partially buried and 765 completely buried craters on Mercury. The elevation profiles of fresh craters were constructed, and by inputting these into a topographic degradation model, we estimated the lava flow thicknesses around partially buried craters. Along the edges of the northern smooth plains, lava flow thicknesses were inverted to be 23–536 m with a median of 228 m. Lava flow thicknesses on Mercury are twice that on the Moon, possibly due to a denser crust on Mercury that favors the ascent of magmas or to higher production rates of magmas. The topographic diffusivity used for crater degradation on Mercury is 3 times that for lunar craters, which is likely a result of a higher cratering rate on Mercury. Plain Language Summary The thickness of lava flows is key to understanding volcanic processes on a planetary body. On Mercury, impact craters whose distal ejecta were subsequently flooded by lava flows are widely seen in the volcanic plains, providing a method to constrain lava flow thicknesses. For those craters whose entire rim is still visible, we estimated the regional lava flow thickness by modeling how the crater shape topographically degrades with time. Our results show that lava flows on Mercury are thicker than on the Moon, possibly because the magma can propagate upward more easily as a result of a denser crust, or perhaps because of higher internal magma production rates. Our findings also suggest that craters on Mercury degrade faster than on the Moon, which is most likely a result of a higher impact bombardment rate. Key Points Lava flow thicknesses on Mercury were estimated by modeling the topographic degradation of partially buried impact craters The median thickness of lava flows on Mercury is 228 m, which is greater than on the Moon by a factor of 2 The reference topographic diffusivity on Mercury is 7.3 m2/Myr, implying that topographic degradation is 3 times greater than on the Moon