Apollo 11 landing site – The Sea of Tranquility (50th anniversary special)

Seen here is the landing site for NASA’s Apollo 11 spacecraft. On July 20, it will be 50 years since humans first landed on an extraterrestrial object.

Apollo 11 landing site in the Sea of Tranquility. Credit: Soerfm on Wikipedia

All the large mare areas (dark, solidified lava plains) on the Moon are actually part of deep basins. These basins are massive impact craters formed during the time of Late Heavy Bombardment period in the solar system. During this period, ~4.1 to 3.8 billion years ago, large asteroid collisions with all planets (and moons) were rampant.

The ‘Sea of Tranquility’ is one such giant basin formed during the Late Heavy Bombardment. Notably, the arc-shaped mountain ranges of Mare Imbrium and Orientale aren’t prominent in this mare basin.

Apollo 11 landing site captured by NASA’s Lunar Reconnaissance Orbiter (LRO), showing the Lunar Module (LM), Lunar Ranging RetroReflector (LRRR) and Passive Seismic Experiment Package (PSEP). Source: LROC blog

Apollo 11 brought back 20 kg of soil samples from the landing region. The fine soil was determined to be basaltic in nature and heavily weathered by the charged particles and radiation in the solar wind. Age dating of the samples revealed the soil’s age to be younger than the basin itself.

Apollo 11 contained millimetric fragments of rocks thrown off from the lunar highlands. The highlands represent material from the crust and its composition was found to be in line with the now-leading formation theory for the Moon’s origin.

The Sea of Tranquility has few unique characteristics of all mare areas. It is metal-rich compared to the rest of the Moon, as evident under enhanced image processed techniques. And it lacks a mascon (gravitational high) at its center.

Rocks in the Apollo 11 landing region were found to have glass-lined tiny craters. Glass patches were found in the beds of ~1 m wide craters.

Apollo missions forever changed our understanding of the Moon’s orgin. Here’s hoping that the renewed global frenzy of going to the Moon stays and we unravel the dozens of scientific mysteries the Moon contains.



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