Lunar Probe
Mare · Near side

Mare Tranquillitatis

A dark basaltic plain on the lunar near side best known as the region containing the Apollo 11 landing site.

Feature typeMare
RegionNear side
Approximate scale873 km
LocationNear-side equatorial region
LOLA topographic map of Mare Tranquillitatis with the Apollo 11 landing area marked
LOLA topographic map of Mare Tranquillitatis with the Apollo 11 landing area marked. Credit: NASA/GSFC. View the NASA source and download information.
Mare TranquillitatisBasalt-flooded impact-basin terrain · schematic locator aid
The schematic separates the landform concept from the spacecraft or telescope image above.

What you are looking at

Mare Tranquillitatis is a broad dark plain made of basaltic lava flows. Its smoother, lower-albedo surface contrasts strongly with the brighter, more heavily cratered highlands around it.

How it formed and changed

Large impacts created low terrain that was later flooded by multiple episodes of basaltic volcanism. Variations in basalt composition and age record changes in mantle melting and volcanic activity.

What scientists learn here

Apollo 11 samples supplied direct laboratory measurements of mare basalt and regolith from this region. Those samples helped calibrate remote sensing and provided radiometric ages that connect crater densities with absolute chronology.

How to find and observe Mare Tranquillitatis

The mare is easy to identify with the unaided eye as part of the dark near-side pattern. Binoculars reveal its boundaries; telescopes show small craters, wrinkle ridges and the transition into adjacent maria and highlands.

Nearby landmarks and exploration context

Mare Serenitatis lies to the north, Mare Fecunditatis to the east and Sinus Asperitatis toward the south-west. The Apollo 11 landing site lies in the south-western part of the mare.

Why this feature matters

It connects lunar volcanism, telescopic geography and the history of human exploration.

Check lunar phaseCompare dates and illumination before observing.Plan an observing sessionUse phase-based target suggestions and keep the terrain in context.