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
- M. F. Wolf
- Discovery site
- Heidelberg Obs.
- Discovery date
- 11 March 1921
- Pronunciation
- / ˈ h ɛ l /
- Named after
- Hel ( Norse mythology )
- Alternative designations
- A921 EM · 1952 DN, 1954 SN 1 · 1921 JK
- Minor planet category
- main-belt · ( outer ) , background
- Observation arc
- 91.34 yr (33,361 d)
- Aphelion
- 3.5804 AU
- Perihelion
- 2.4255 AU
- Semi major axis
- 3.0029 AU
- Orbital period sidereal
- 5.20 yr (1,901 d)
- Mean anomaly
- 358.26 °
- Mean motion
- 0° 11 21.84 / day
- Inclination
- 10.701°
- Longitude of ascending node
- 321.17°
- Argument of perihelion
- 249.54°
- Mean diameter
- 60.98 ± 0.74 km 63.494 ± 0.743 km 63.56 ± 4.01 km 69.17 ± 1.4 km
via Wikipedia infobox
Wikidata facts
- Diameter
- 63.494
- Orbital period
- 1893.801042098274
Show 14 more facts
- provisional designation
- A921 EM
- time of discovery or invention
- 1921-03-11
- orbital inclination
- 10.64162518647909
- albedo
- 0.058
- rotation period
- 16.43
- absolute magnitude
- 9.79
- orbital eccentricity
- 0.2002528378505879
- semi-major axis of an orbit
- 2.9956468649008
- periapsis
- 2.395760079006198
- apoapsis
- 3.595533650795402
- longitude of ascending node
- 320.5968489846272
- argument of periapsis
- 251.5311713232487
- mean anomaly
- 15.47429294909575
- time of periapsis
- 2460919.0965774646
Sources (2)
via Wikidata · CC0
~4 min read
Article
949 Hel (prov. designation: A921 EM or 1921 JK) is a dark background asteroid from the outer regions of the asteroid belt, approximately 63 kilometers (39 miles) in diameter. It was discovered by German astronomer Max Wolf at the Heidelberg Observatory on 11 March 1921. The transitional X-type asteroid has a rotation period of 8.2 hours. It was named in memory of the discoverer, after the Norse goddess of the dead, Hel.
Orbit and classification