File:225_Henrietta.png · Wikimedia Commons · See Wikimedia Commons
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
- 19 April 1882
- Pronunciation
- / h ɛ n r i ˈ ɛ t ə /
- Named after
- Henrietta Jansen
- Alternative designations
- A882 HA
- Minor planet category
- Main belt ( Cybele )
- Observation arc
- 120.87 yr (44,148 d)
- Aphelion
- 4.28364 AU (640.823 Gm )
- Perihelion
- 2.4945 AU (373.17 Gm)
- Semi major axis
- 3.38907 AU (506.998 Gm)
- Orbital period sidereal
- 6.24 yr (2,278.9 d)
- Average orbital speed
- 16.2 km/s
- Mean anomaly
- 159.155 °
- Mean motion
- 0° 9 28.703 / day
- Inclination
- 20.872°
- Longitude of ascending node
- 197.113°
- Argument of perihelion
- 104.149°
- Dimensions
- 120.49 ± 2.5 km
via Wikipedia infobox
~2 min read
Encyclopedic overview
225 Henrietta is a very large outer main-belt asteroid. It was discovered by Austrian astronomer Johann Palisa on April 19, 1882, in Vienna and named after Henrietta, wife of astronomer Pierre J. C. Janssen. The asteroid is orbiting at a distance of 3.39 AU from the Sun with a period of 6.24 years and an eccentricity (ovalness) of 0.26. The orbital plane is inclined at an angle of 20.9° to the plane of the ecliptic. 225 Henrietta belongs to Cybele group of asteroids.
This is classified as a C-type asteroid and is probably composed of primitive carbonaceous material. It has a very dark surface, with an albedo of 0.040. Photometric measurements made from the Oakley Southern Sky Observatory during 2012 gave a light curve with a period of 7.352±0.003 h and a variation in brightness of 0.18±0.02 in magnitude. This is consistent with a synodic rotation period of 7.356±0.001 h determined in 2000. In 2001, the asteroid was detected by radar from the Arecibo Observatory at a distance of 1.58 AU. The resulting data yielded an effective diameter of 128±16 km.
Excerpted from Wikipedia’s “225 Henrietta” article, available under the CC BY-SA 4.0 licence.