Sea / bay

Mare Nubium

The Sea of Clouds is an irregular dark region south of the lunar equator. Partly buried formations and neighbouring highlands make its borders varied.

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Mare Nubium and surrounding lunar terrain in the LROC Wide Angle Camera mosaic
Mare Nubium · North up, east right. Open image ↗
NASA / GSFC / Arizona State University · LROC WAC mosaic via USGS. Regional map crop; lighting is fixed and does not follow the selected date.
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How to observe Mare Nubium

Search its eastern portion for Rupes Recta. Use a wide field to compare the darker plain with the bright cratered terrain.

Finding the region

Look at 20.59° S, 17.29° W on the lunar disc. The chart marker identifies the catalogue centre. Start with a wide field and use the nearby formations below as landmarks.

Equipment & conditions

These dark plains are a good starting point with binoculars. Trace their shapes at low power, then examine the boundary with the brighter highlands. Higher sunlight helps reveal brightness differences; low sunlight brings out ridges.

Lighting

For surface relief, try a time when the Sun is low over this region. To compare surface brightness and any bright rays, return under higher illumination. The atlas calculates the solar elevation at the formation’s centre for any selected date.

View Mare Nubium in the atlas →

IAU / USGS Gazetteer

Official feature record

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Approved name
Mare Nubium
Feature classification
Mare, maria
Catalogue dimension / extent
714.50 km
Centre latitude
20.59° S
Centre longitude
17.29° W
Name origin (Gazetteer)
"Sea of Clouds."

Selenographic coordinates · East-positive longitude · Catalogue extent · Updated 2026-09-16

Nearby formations

LROC photograph of Rupes RectaValley / rille / scarp

Rupes Recta

The Straight Wall is a linear scarp in Mare Nubium. Its appearance depends strongly on the direction and height of the sunlight.

116 kmRead guide ↗
LROC photograph of AlpetragiusImpact crater

Alpetragius

A smaller crater west of the Alphonsus–Arzachel region. Its unusually prominent central feature gives it a distinctive appearance.

40 kmRead guide ↗
LROC photograph of ArzachelImpact crater

Arzachel

The southern crater of a recognisable central chain with Ptolemaeus and Alphonsus. It has a central peak and clearly defined inner walls.

97 kmRead guide ↗
LROC photograph of AlphonsusImpact crater

Alphonsus

The middle crater of the Ptolemaeus–Alphonsus–Arzachel chain. Its floor and modest central peak contrast with the neighbouring formations.

110.5 kmRead guide ↗