57 Mnemosyne

Also known as (57) Mnemosyne, Mnemosyne

main-belt asteroid

Picture of the Day · NASA

Pathfinder on Mars

2026-07-04

On July 4th, 1997, using its own array of fireworks, a parachute, and a cocoon of airbags, the Mars Pathfinder spacecraft bounced like a giant beach ball at least 15 times before it came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. After its then novel airbag-assisted landing sequence was completed, Pathfinder transmitted this color mosaic to mission operators on Earth. In the scene from another world, the Mars Sojourner robot rover is visible in the foreground, crouched on top of the unfolded Pathfinder. About the size of a large house cat, the six-wheeled, solar-powered Sojourner became the first successful Martian rover. Surrounding Pathfinder are deflated airbags and the rock-strewn terrain of the Ares Vallis floodplain. In the distance Martian hills appear against a dusty brownish sky. The Pathfinder lander was subsequently renamed the Carl Sagan Memorial Station.

via NASA APOD

Key facts

Discovered by: Karl Theodor Robert Luther
Discovery date: 22 September 1859
Pronunciation: / n ɪ ˈ m ɒ s ɪ n iː /
Named after: Mnemosyne
Minor planet category: Main belt
Adjectives: Mnemosynean / ˌ n ɛ m ə s ɪ ˈ n iː ə n / , Mnemosynian / n ɛ m ə ˈ s ɪ n i ə n /
Aphelion: 526.785 Gm (3.521 AU )
Perihelion: 415.379 Gm (2.777 AU)
Semi major axis: 471.082 Gm (3.149 AU)
Orbital period sidereal: 2,041.056 d (5.59 a )
Mean anomaly: 68.001°
Inclination: 15.200°
Longitude of ascending node: 199.337°
Argument of perihelion: 212.848°
Dimensions: 112.59 ± 2.8 km
Synodic rotation period: 25.324 ± 0.002 h
Spectral type: S

via Wikipedia infobox

~1 min read

Encyclopedic overview

57 Mnemosyne is a large main belt asteroid. It is a stony S-type asteroid in composition. This object was discovered by Robert Luther on 22 September 1859 in Düsseldorf. Its name was chosen by Martin Hoek, the director of the Utrecht Observatory, in reference to Mnemosyne, a Titaness in Greek mythology.

This asteroid is orbiting in the outer main belt at a distance of 3.149 AU from the Sun with an eccentricity (ovalness) of 0.118 and a period of 5.58811 a. The orbital plane is inclined at an angle of 15.2° to the ecliptic. The orbital period of this asteroid is close to a 2:1 commensurability with Jupiter, which made it useful for perturbation measurements to derive the mass of the planet.

Excerpted from Wikipedia’s “57 Mnemosyne” article, available under the CC BY-SA 4.0 licence.