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
- K. Reinmuth
- Discovery site
- Heidelberg
- Discovery date
- 9 August 1923
- Alternative designations
- 1923 NW
- Observation arc
- 92.68 yr (33850 days)
- Aphelion
- 3.1787 AU (475.53 Gm )
- Perihelion
- 2.0450 AU (305.93 Gm)
- Semi major axis
- 2.6118 AU (390.72 Gm)
- Orbital period sidereal
- 4.22 yr (1541.8 d )
- Mean anomaly
- 352.050 °
- Mean motion
- 0° 14 0.6 / day
- Inclination
- 9.7603°
- Longitude of ascending node
- 214.972°
- Argument of perihelion
- 128.034°
- Mean radius
- 8.95 km
- Synodic rotation period
- 22.77 h (0.949 d )
- Geometric albedo
- 0.1994 ± 0.051
via Wikipedia infobox
Wikidata facts
- Instance of
- asteroid
- Named after
- Franz Xaver von Zach
- Followed by
- 1000 Piazzia
- Follows
- 998 Bodea
- Parent body
- Sun
- Minor-planet group
- asteroid belt
- Diameter
- 16.848
- Orbital period
- 1542.789584034522
Show 17 more facts
- discoverer or inventor
- Karl Wilhelm Reinmuth
- site of astronomical discovery
- Heidelberg-Königstuhl State Observatory
- provisional designation
- A923 PE
- time of discovery or invention
- 1923-08-09
- orbital inclination
- 9.754830723586485
- orbital eccentricity
- 0.2158520433899294
- albedo
- 0.226
- absolute magnitude
- 10.9
- periapsis
- 2.048975958045723
- apoapsis
- 3.177017276454555
- semi-major axis of an orbit
- 2.612996617250139
- mean anomaly
- 65.88021357015587
- longitude of ascending node
- 214.8905394236184
- argument of periapsis
- 128.0113395854948
- rotation period
- 22.837
- time of periapsis
- 2460718.168590861
- epoch
- November 21, 2025
Sources (2)
via Wikidata · CC0
~1 min read
Encyclopedic overview
999 Zachia is a main-belt asteroid that was discovered by German astronomer Karl W. Reinmuth in 1923 and named after Hungarian astronomer Franz Xaver von Zach.
Photometric observations of this asteroid collected during 1999 show a rotation period of 22.77 ± 0.03 hours with a brightness variation of 0.3 magnitude.
Excerpted from Wikipedia’s “Q459031” article, available under the CC BY-SA 4.0 licence.