Key Facts


Mnemosyne is a large asteroid orbiting between Mars and Jupiter in the main portion of the asteroid belt. NASA JPL has not classified Mnemosyne as potentially hazardous because its orbit does not bring it close to Earth.

Mnemosyne orbits the sun every 2,050 days (5.61 years), coming as close as 2.81 AU and reaching as far as 3.50 AU from the sun. Mnemosyne is about 112.6 kilometers in diameter, making it larger than 99% of asteroids, comparable in size to the U.S. state of Delaware.

The rotation of Mnemosyne has been observed. It completes a rotation on its axis every 25.32 hours.

Mnemosyne's spectral type S (Tholen) / S (SMASSII) indicates that it is likely to contain and .

No Close Approaches

Mnemosyne's orbit is 1.83 AU from Earth's orbit at its closest point. This means that there is an extremely wide berth between this asteroid and Earth at all times.

Orbital simulations conducted by NASA JPL's CNEOS do not show any close approaches to Earth.

Images and Observations

Mnemosyne's orbit is determined by observations dating back to Dec. 22, 1859. It was last officially observed on July 7, 2022. The IAU Minor Planet Center records 3,438 observations used to determine its orbit.

Accessibility and Exploration

This asteroid is not considered a viable target for human exploration by the NHATS study.

Similar Objects

These objects have orbits that share similar characteristics to the orbit of Mnemosyne:



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Orbital Elements

  • Epoch: 2459800.5 JD
  • Semi-major axis: 3.154 AU
  • Eccentricity: 0.109
  • Inclination: 15.24°
  • Longitude of Ascending Node: 198.9°
  • Argument of Periapsis: 210.52°
  • Mean Anomaly: 354.48°

Physical Characteristics

  • Diameter: 112.59000 km
  • Magnitude: 7.05
  • Albedo: 0.2149
  • Spectral type (Tholen): S
  • Spectral type (SMASS): S

Derived Characteristics

  • Orbit Period: 2,050 days (5.61 years)
  • Avg. Orbit Speed: 16.74 km/s
  • Aphelion Distance: 3.50 AU
  • Perihelion Distance: 2.81 AU
  • Rotation Period: 25.32 hours
  • Approx. Composition: and .

Map Comparison

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Orbit Simulation

Sky Map

The position of Mnemosyne is indicated by a ◯ pink circle. Note that the object may not be in your current field of view. Use the controls below to adjust position, location, and time.