Links
- Wikipedia
- Proteus on Wikipedia
Proteus
Details
Proteus is Neptune's largest inner moon, a dark irregular body discovered by Voyager 2 in 1989. It keeps a box-like shape near the threshold where gravity would round it out, while its battered dark surface shows no clear sign of geological remodeling.
Proteus matters because it is not just a smaller version of Triton. It is Neptune's largest inner moon, discovered only when Voyager 2 reached the system, and it remains irregular rather than round. NASA describes it as a box-like body so close to the threshold of roundness that a little more mass could have let gravity pull it into a sphere.
That almost-world quality fits its surface. Proteus is dark, heavily cratered, and shows no clear sign of geological modification, so its importance comes less from activity than from preservation. It keeps a battered record of impacts in Neptune's inner satellite region.
One impact story may still be visible in the modern system. NASA reports that Hippocamp, a tiny moon orbiting near Proteus, is likely a fragment knocked off the larger moon by a comet collision billions of years ago. Proteus therefore reads as both a surviving inner moon and a source body, a dark irregular world whose history may have left debris still orbiting Neptune.
191km
Key facts
- Category
- Moons
- Object class
- Small inner moon
- Scale fact
- 436 kmmaximum extent
- Host
- Neptune
Scale context
Where Proteus sits on the full axis
Together, these objects make the size change around Proteus easy to compare at a glance.
Sources
References for Proteus
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- Proteus — Wikipedia
- Visual reference: Wikimedia Commons (Voyager 2 1989 / NASA, Public domain)
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.