Facts about Mercury
- 12
Mercury's surface pressure measures only 0.5 pascals, making its atmosphere trillionth of Earth's atmospheric density and classifying it as an exosphere rather than a true atmosphere.
- 11
Only two spacecraft have ever visited Mercury: Mariner 10 in 1974-1975 and NASA's MESSENGER probe, which orbited from 2011 to 2015 before intentionally crashing into the surface.
- 10
A thick, tenuous atmosphere composed primarily of oxygen, sodium, hydrogen, and helium continuously escapes Mercury's surface due to solar wind bombardment and weak gravitational pull.
- 09
Radar observations have detected a large radar-bright region near Mercury's north pole that scientists believe could contain subsurface water ice shielded by overlying insulating material.
- 08
Sunlight takes only 3.2 minutes to reach Mercury, the closest planet to the Sun at an average distance of 57.9 million kilometers.
- 07
Iron comprises approximately 85 percent of Mercury's core, making it proportionally larger and denser than Earth's core relative to the planet's overall size.
- 06
Mercury's solar day lasts 176 Earth days, meaning the planet rotates so slowly that its year is only half as long as its day.
- 05
Observations by NASA's MESSENGER probe from 2011 to 2015 revealed that Mercury possesses water ice deposits in permanently shadowed craters near its poles despite surface temperatures exceeding 430 degrees Celsius.
- 04
With a surface heavily cratered by 4 billion years of meteorite impacts, Mercury resembles Earth's Moon far more than any terrestrial planet.
- 03
Mercury's diameter of 4,879 kilometers makes it smaller than Jupiter's moon Ganymede, yet it remains the second-densest planet after Earth.
- 02
Extreme temperature swings of 430 degrees Celsius between Mercury's sunlit and dark sides result from its thin atmosphere's inability to distribute heat.
- 01
At 88 Earth days, Mercury's orbital period around the Sun makes it the fastest-orbiting planet in our solar system.