Known Space   --   Sol   --  

Mercury


Mercury is a scorched, airless world, closest to the Sun. Ices and minerals with low melting points have been boiled away leaving a high density world. Mercury has a very slow rotation - it spins once in 59 days relative to the stars - and goes round the Sun once every 88 days. On average there are 176 earth days between one sunrise and the next. Because of this slow day, temperatures can reach upto +360 degrees C during the day but drop to -170 degrees C at night (making it one of the coldest places in the Solar System!). These temperature extremes cause thermal erosion of the rocks and produce dust. Amazingly, there is water ice in the protected shadows of some of the craters in the north polar region.

The surface of Mercury has enormous escarpments, some hundreds of kilometers long and upto three kilometers high. The largest feature on the surface is the Caloris Basin, a 1300 km diameter impact crater. In addition to regions of heavily cratered terrain Mercury also has regions of smooth plains, the result of volcanic activity in the ancient past. There is no recent volcanic activity. Mercury has a small magnetic field about 1% the strength of Earth's magnetic field.

The fact that Mercury rotates three times in two of its years, combined with the high eccentricity can make for some strange observations on the surface. At some latitudes the observer would see the Sun rise and then gradually increase in apparent size as it slowly moved towards the zenith. At that point the Sun would stop, briefly reverse course, and then stop again before resuming its path towards the horizon and decreasing in apparent size. All the while the stars would be moving three times faster across the sky.


Orbital Distance:   0.306 AU - 0.467 AU (average 0.387 AU)
Eccentricity:       0.206
Local Year:         87.969 days
Orbital Velocity:   47.87 km/s (average)
Inclination:        7.004°
Local Day:          58.646 day
Axial Tilt:         None

Diameter:           4,878 km
Composition:        Nickel-iron, silicates
Density:            5.44 g/cm3
Mass:               3.3 x 1017 tonnes (0.055 earths)
Gravity:            0.380 G
Escape Velocity:    4.25 km/s
Area:               74.754 million km2
Surface Material:   Basaltic dust and rock
Atmosphere:         None
Pressure:           None
Albedo:             0.06
Temperature:        -170°C - +360°C

FAQ - Astronomical Glossary


Copyright © 1996 Trisen Games