Image by NickyPe on Pixabay · Pixabay License
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 , I. Groeneveld
- Discovery site
- Heidelberg Obs.
- Discovery date
- 9 September 1956
- Named after
- Jan Oort (astronomer)
- Alternative designations
- 1956 RB · 1945 TD, 1947 DA · 1950 PZ, 1950 RU · 1951 XW, 1955 MW · 1956 SD, 1964 DA · A917 TD
- Minor planet category
- main-belt · Themis
- Observation arc
- 71.42 yr (26,086 days)
- Aphelion
- 3.7153 AU
- Perihelion
- 2.6084 AU
- Semi major axis
- 3.1618 AU
- Orbital period sidereal
- 5.62 yr (2,054 days)
- Mean anomaly
- 240.25 °
- Inclination
- 1.0860°
- Longitude of ascending node
- 174.55°
- Argument of perihelion
- 232.69°
- Dimensions
- 27.13 km (calculated) , 33.163 ± 0.534 km , 33.644 ± 0.267 , 37.37 ± 0.74 km
- Synodic rotation period
- 10.2684 ± 0.0005 h , 10.2705 ± 0.0004 h
- Geometric albedo
- 0.053 ± 0.002 , 0.065 ± 0.011 , 0.0672 ± 0.0150 , 0.10 (assumed)
via Wikipedia infobox
Wikidata facts
- Instance of
- asteroid
- Named after
- Jan Hendrik Oort
- Followed by
- 1692 Subbotina
- Follows
- Q142409
- Parent body
- Sun
- Minor-planet group
- asteroid belt
- Diameter
- 33.644
- Orbital period
- 2055.228571722609
- Image
- 1691Oort (Lightcurve Inversion).png
Show 19 more facts
- discoverer or inventor
- Ingrid van Houten-Groeneveld
- site of astronomical discovery
- Heidelberg-Königstuhl State Observatory
- provisional designation
- A917 TD
- time of discovery or invention
- 1956-09-09
- orbital eccentricity
- 0.1784122194397598
- absolute magnitude
- 10.96
- orbital inclination
- 1.087040226748224
- periapsis
- 2.599132617370861
- apoapsis
- 3.727963960425158
- semi-major axis of an orbit
- 3.163548288898009
- mean anomaly
- 46.20897547372785
- longitude of ascending node
- 174.4788239431713
- argument of periapsis
- 232.6378790849275
- Commons category
- 1691 Oort
- albedo
- 0.065
- rotation period
- 10.2705
- asteroid spectral type
- C-type asteroid
- time of periapsis
- 2460736.6944259345
- epoch
- November 21, 2025
Sources (2)
via Wikidata · CC0
~3 min read
Encyclopedic overview
1691 Oort, provisional designation 1956 RB, is a rare-type carbonaceous Themistian asteroid from the outer region of the asteroid belt, approximately 33 kilometers in diameter.
It was discovered on 9 September 1956, by German astronomer Karl Reinmuth and Dutch astronomer Ingrid van Houten-Groeneveld at Heidelberg Observatory in south-west Germany. It was later named after Dutch astronomer Jan Oort.
Excerpted from Wikipedia’s “1691 Oort” article, available under the CC BY-SA 4.0 licence.