Onyx River
The Onyx River is a seasonal meltwater stream in Antarctica’s McMurdo Dry Valleys, regarded as the continent’s longest river.
Also known as: Onyx River Antarctica
How big is it?
32 km long
Also 19.88 mi
Approximate main-channel length · approximate
Typical recorded range: 28 km to 35 km.
A little perspective
About 1.42 times the representative mean diameter of Phobos.
Phobos: Phobos is the larger and innermost moon of Mars, notable for its irregular shape and heavily cratered surface.
Measurements, assumptions & sources +
Onyx River
Antarctica’s seasonal Onyx River is commonly described as approximately 32 km long. Its meltwater course, active reach and mapped endpoints vary with season and survey convention.
US Antarctic Program — Onyx River
The marked approximate main-channel length is calibrated. Unmeasured illustration details are representative.
Phobos
Mars’s larger moon is irregular, about 27 × 22 × 18 km. The 22.533 km comparison diameter is representative rather than a spherical edge.
The marked representative mean diameter is calibrated. Unmeasured illustration details are representative.
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Why this measurement?
Why we use 32 km
For comparison, this page uses approximate main-channel length. This is labelled approximate; the central value is useful for comparison, while real values or measurement solutions can vary. The recorded range is 28 km to 35 km.
Antarctica’s seasonal Onyx River is commonly described as approximately 32 km long. Its meltwater course, active reach and mapped endpoints vary with season and survey convention.
The marked horizontal span follows the named feature; transparent margins and unmeasured details do not alter it. How calibrated comparisons work →
Recorded properties
Onyx River dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 32 km | 28 km to 35 km | approximate |
Around this scale
Go smaller. Go bigger.
These links use compatible length records, ordered around the selected value.
Nearest lower value · SpacePhobos22.53 kmPhobos is the larger and innermost moon of Mars, notable for its irregular shape and heavily cratered surface.Around the same scale · PeopleOne-hour cycle20 kmA one-hour cycle is the distance covered by cycling at a constant speed for one hour without stopping.
Nearest higher value · SpaceMetis43 kmMetis is an irregularly shaped inner moon of Jupiter, orbiting close to the planet's cloud tops.Sources and method
Want to check the number?
The source records and measurement method remain available for inspection.
- US Antarctic Program — Onyx RiverMcMurdo Dry Valleys geographic context; published river length and active course are approximate.
There’s always another scale
Follow your curiosity.
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SpaceNeutron star20 kmA neutron star is the dense remnant core left after a massive star explodes as a supernova, composed mostly of neutrons.PlacesChallenger Deep10.94 kmChallenger Deep is the deepest known point in the Earth's oceans, located in the Mariana Trench.TransportOne-hour drive at 100 km/h100 kmA one-hour drive at a set speed is the distance a vehicle travels in one hour of uninterrupted motion.
SpaceDeimos12.4 kmDeimos is the smaller and outermost natural satellite of Mars, with an irregular, rocky shape.