86 Semele

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

Friedrich Tietjen

Discovery date

January 4, 1866

Pronunciation

/ ˈ s ɛ m ɪ l ə /

Named after

Semele

Minor planet category

Main belt

Adjectives

Semelean / s ɛ m ɪ ˈ l eɪ ə n /

Aphelion

562.652 million km (3.761 AU)

Perihelion

369.116 million km (2.467 AU)

Semi major axis

465.884 million km (3.114 AU )

Orbital period sidereal

2,007.366 d (5.50 a )

Average orbital speed

16.69 km/s

Mean anomaly

264.875°

Inclination

4.822°

Longitude of ascending node

86.452°

Argument of perihelion

307.886°

Dimensions

120.6 km

Mass

1.8 × 10 kg

Equatorial surface gravity

0.0337 m/s²

via Wikipedia infobox