Skip to content
EntityQ158511· pop 36· linked from 7 articles

Also known as (996) Hilaritas, Hilaritas

main-belt asteroid

Picture of the Day · NASA

Pathfinder on Mars

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
J. Palisa
Discovery site
Vienna
Discovery date
21 March 1923
Pronunciation
/ h ɪ ˈ l ær ɪ t æ s /
Alternative designations
1923 NM
Observation arc
88.16 yr (32200 days)
Aphelion
3.5220 AU (526.88 Gm )
Perihelion
2.6535 AU (396.96 Gm)
Semi major axis
3.0878 AU (461.93 Gm)
Orbital period sidereal
5.43 yr (1981.8 d )
Mean anomaly
93.831 °
Mean motion
0° 10 53.94 / day
Inclination
0.65948°
Longitude of ascending node
347.404°
Argument of perihelion
147.140°
Mean radius
14.765 ± 0.65 km
Synodic rotation period
10.05 h (0.419 d )
Geometric albedo
0.0901 ± 0.009

via Wikipedia infobox

~1 min read

Encyclopedic overview

996 Hilaritas is a Themistian asteroid. It was discovered in 1923 by Austrian astronomer Johann Palisa. Following Palisa's death in 1925, this asteroid was named for a "happy or contented mind"; qualities associated with the discoverer.

Photometric observations of this asteroid collected during 2010 show a rotation period of 10.052 ± 0.001 hours with a brightness variation of 0.65 ± 0.03 magnitude.

Excerpted from Wikipedia’s “Q158511” article, available under the CC BY-SA 4.0 licence.