Image by Liliya_Arslanova 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
- Johann Palisa
- Discovery date
- 25 April 1890
- Alternative designations
- A890 HA, 1954 UJ 3
- Minor planet category
- main-belt
- Observation arc
- 124.62 yr (45516 d)
- Aphelion
- 2.4273 AU (363.12 Gm )
- Perihelion
- 2.01631 AU (301.636 Gm)
- Semi major axis
- 2.22182 AU (332.380 Gm)
- Orbital period sidereal
- 3.31 yr (1209.7 d )
- Mean anomaly
- 115.293 °
- Mean motion
- 0° 17 51.382 / day
- Inclination
- 1.8555°
- Longitude of ascending node
- 161.655°
- Argument of perihelion
- 331.580°
- Dimensions
- 14.97 ± 1.1 km , 19×12×11 km
- Mass
- ~
- Mean density
- ~2.7 g/cm
- Synodic rotation period
- 4.313 h (0.1797 d ) , 0.180 d (4.32 h)
via Wikipedia infobox
Wikidata facts
- Instance of
- asteroid
- Followed by
- 292 Ludovica
- Follows
- 290 Bruna
- Parent body
- Sun
- Minor-planet group
- asteroid belt
- Diameter
- 10.456
- Orbital period
- 1209.578977774755
- Image
- 291Alice (Lightcurve Inversion).png
Show 18 more facts
- discoverer or inventor
- Johann Palisa
- site of astronomical discovery
- Vienna Observatory
- provisional designation
- A890 HA
- time of discovery or invention
- 1890-04-25
- orbital inclination
- 1.857392100495459
- albedo
- 0.425
- Commons category
- 291 Alice
- rotation period
- 4.313
- absolute magnitude
- 11.56
- orbital eccentricity
- 0.0926227369373859
- semi-major axis of an orbit
- 2.221726195248328
- periapsis
- 2.015943834318943
- apoapsis
- 2.427508556177714
- longitude of ascending node
- 161.5511607288823
- argument of periapsis
- 331.6411624478351
- mean anomaly
- 46.95997527960427
- time of periapsis
- 2460842.7172252918
- epoch
- November 21, 2025
Sources (2)
via Wikidata · CC0
~1 min read
Encyclopedic overview
291 Alice is a stony background asteroid from the inner region of the asteroid belt. It was discovered by Johann Palisa on 25 April 1890 at the Vienna Observatory.
Photometric observations of this asteroid at the Leura Observatory in Leura, Australia during 2006 gave a rotation period of 4.313 ± 0.002 hours and a brightness variation of 0.20 ± 0.02 in magnitude. This result is in agreement with previous studies. Lightcurve analysis indicates that Alice's pole points towards either ecliptic coordinates (β, λ) = (55°, 65°) or (β, λ) = (55°, 245°) with a 10° uncertainty. This gives an axial tilt of about 35° in both cases.
Excerpted from Wikipedia’s “291 Alice” article, available under the CC BY-SA 4.0 licence.