The Solar System – Mercury
Technical Data
| Date of Issue | March 20, 2018 |
|---|---|
| Denomination | Rs. 5 |
| Quantity | 500,000 |
| Perforation | 3½ x 13 |
| Printer | Security Printing Press, Hyderabad |
| Printing Process | Wet Offset |
| Watermark | No Watermark |
| Colors | Multicolor |
| Credit (Designed By) | Mr. Suresh Kumar Smt. Alka Sharma |
| Catalog Codes |
Michel IN 3369 Yvert et Tellier IN 3058 Stanley Gibbons IN 3482 |
| Themes | Outer Space | Planets |
The Innermost Planet
Mercury, the smallest and innermost planet in the Solar System, is a rocky and metallic world that races around the Sun faster than any other planet. With an orbital period of only 88 Earth days, it completes a year in less than three months, earning its name from the Roman messenger god renowned for his speed. Despite its proximity to the Sun, Mercury remains a world of extremes — silent, cratered, and full of contrasts.
Physical Characteristics
Mercury’s equatorial radius is 2,439.7 kilometres, which is about 0.38 times that of Earth. Though small, it has a remarkably high density of 5.427 g/cm³, making it the second densest planet in the Solar System, just slightly less than Earth. This density indicates that Mercury is largely composed of metallic (70%) and silicate (30%) materials.
Its surface is heavily cratered and resembles that of our Moon, revealing a planet shaped by countless meteor impacts over billions of years. Mercury has no substantial atmosphere, allowing solar radiation to strike its surface directly and contributing to dramatic temperature fluctuations.
Temperature Extremes
Due to the lack of atmosphere, Mercury experiences some of the most extreme temperature variations of any planet. Surface temperatures range from a frigid 100 K (-173°C) during the night to an intense 700 K (427°C) in the daytime. These fluctuations make Mercury both one of the coldest and hottest places in the Solar System.
A World Without Air
Mercury’s atmosphere is virtually absent, consisting only of trace amounts of oxygen, sodium, hydrogen, helium, and potassium. This tenuous exosphere cannot retain heat or shield the surface from solar winds, which continually bombard the planet, stripping away its particles. As a result, Mercury’s sky remains dark even during its daytime.
A Rocky Relic of the Early Solar System
As one of the four terrestrial planets, Mercury offers valuable clues about the formation of the Solar System. Scientists believe that its large metallic core and thin crust may have formed after massive collisions that stripped away much of its outer layers. Mercury thus stands as a fossilized witness to the Solar System’s earliest and most violent epoch.
Philatelic Tribute to Mercury
To honour this fascinating planet, the Department of Posts issued a commemorative postage stamp on Mercury as part of its Solar System series. The stamp artistically depicts the grey, cratered surface of Mercury, bathed in sunlight, capturing both its desolate beauty and its scientific significance.
This philatelic release celebrates Mercury as a symbol of speed, endurance, and cosmic mystery — the Sun’s closest companion and a messenger from the dawn of planetary history.