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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
- David H. Levy and Henry Holt
- Discovery date
- 20 June 1990
- Pronunciation
- / j ʊ ˈ r iː k ə / yuurr- EE -kə
- Named after
- Eureka
- Alternative designations
- 1990 MB
- Minor planet category
- Martian L5
- Observation arc
- 13267 days (36.32 yr)
- Aphelion
- 1.6222 AU (242.68 Gm )
- Perihelion
- 1.4249 AU (213.16 Gm)
- Semi major axis
- 1.5236 AU (227.93 Gm)
- Orbital period sidereal
- 1.88 yr (686.89 d )
- Average orbital speed
- 24.11 km/ s
- Mean anomaly
- 145.29 °
- Mean motion
- 0° 31 26.76 / day
- Inclination
- 20.280°
- Longitude of ascending node
- 245.057°
- Argument of perihelion
- 95.456°
- Earth moid
- 0.497052 AU (74.3579 Gm)
via Wikipedia infobox
Wikidata facts
- Diameter
- 1.878
- Orbital period
- 686.8434787518037
Show 15 more facts
- provisional designation
- 1990 MB
- time of discovery or invention
- 1990-06-20
- orbital inclination
- 20.28191958842011
- orbital eccentricity
- 0.06487352882090523
- absolute magnitude
- 16.1
- albedo
- 0.182
- periapsis
- 1.424655697335888
- apoapsis
- 1.622324024111949
- semi-major axis of an orbit
- 1.523489860723918
- mean anomaly
- 232.030112742215
- longitude of ascending node
- 245.0131768515497
- argument of periapsis
- 95.54274760031726
- Commons category
- 5261 Eureka
- rotation period
- 2.6902
- time of periapsis
- 2461244.65356261
via Wikidata · CC0
~3 min read
Article
5261 Eureka is the first Mars trojan discovered. It was discovered by David H. Levy and Henry Holt at Palomar Observatory on 20 June 1990. It trails Mars (at the L5 point) at a distance varying by only 0.3 AU during each revolution (with a secular trend superimposed, changing the distance from 1.5–1.8 AU around 1850 to 1.3–1.6 AU around 2400). Minimum distances from Earth, Venus, and Jupiter, are 0.5, 0.8, and 3.5 AU, respectively.
Long-term numerical integration shows that the orbit is stable. Kimmo A. Innanen and Seppo Mikkola note that "contrary to intuition, there is clear empirical evidence for the stability of motion around the L4 and L5 points of all the terrestrial planets over a timeframe of several million years".