78 Diana

Also known as (78) Diana, Diana

main-belt asteroid

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: Karl Theodor Robert Luther
Discovery date: March 15, 1863
Pronunciation: / d aɪ ˈ æ n ə , d aɪ ˈ eɪ n ə / dy- A(Y)N -ə
Named after: Diāna (Roman mythology)
Minor planet category: Main belt
Adjectives: Dianian ( / d aɪ ˈ eɪ n i ə n / dy- AY -nee-ən )
Aphelion: 473.182 Gm (3.163 AU )
Perihelion: 310.686 Gm (2.077 AU)
Semi major axis: 391.934 Gm (2.620 AU)
Orbital period sidereal: 1,548.922 d (4.24 yr)
Average orbital speed: 18.20 km/s
Mean anomaly: 353.808°
Inclination: 8.688°
Longitude of ascending node: 333.582°
Argument of perihelion: 151.423°
Dimensions: 123.63 ± 4.57 km
Mass: (1.27 ± 0.13) × 10 kg
Mean density: 1.28 ± 0.19 g/cm

via Wikipedia infobox

~1 min read

Encyclopedic overview

78 Diana is a large and dark main-belt asteroid. It was discovered by German astronomer Robert Luther on March 15, 1863, and named after Diana, Roman goddess of the hunt. The asteroid is orbiting the Sun at a distance of 2.620 AU with a period of 4.24 years and an eccentricity (ovalness) of 0.207. The orbital plane is tilted at an angle of 8.688° relative to the plane of the ecliptic. Its composition is carbonaceous and primitive.

Photometric observations of this asteroid during 1986 and 2006–08 gave a light curve with a rotation period of 7.2991 hours and a brightness variation in the range 0.02–0.104 magnitude. Based upon radar data, the near surface solid density of the asteroid is 2.7 −0.5 g cm. 78 Diana occulted a star on September 4, 1980. A diameter of 116 km was measured, closely matching the value given by the IRAS satellite.

Excerpted from Wikipedia’s “78 Diana” article, available under the CC BY-SA 4.0 licence.