1. Overview of Mercury
- Position in Solar System: 1st planet from the Sun
- Distance from Sun: ~57.9 million km (0.39 AU)
- Orbital Period: 88 Earth days (1 Mercury year)
- Rotation Period: 59 Earth days (1 Mercury day)
- Diameter: 4,880 km (about 38% of Earth’s)
- Gravity: 3.7 m/s² (38% of Earth’s)
- Temperature:
- Daytime: Up to 430°C (800°F)
- Nighttime: Down to -180°C (-290°F)
- Moons: None
- Atmosphere: Thin exosphere (oxygen, sodium, hydrogen, helium, potassium)
2. Key Characteristics
- Size: Smallest planet in the solar system.
- Surface: Cratered and similar to the Moon, covered in dust and rock.
- Color: Dark gray.
- Core: Large metallic core (accounts for about 85% of its radius).
- Density: Second densest planet (after Earth).
- No Tilt: Almost no axial tilt (0.034°), meaning minimal seasons.
3. Orbital and Rotational Facts
- Orbital Speed: 47.87 km/s (fastest planet).
- Eccentric Orbit: Highly elliptical; distance from the Sun varies greatly.
- 1 Day-Night Cycle: 176 Earth days (due to spin-orbit resonance).
- Tidal Locking: Experiences 3 rotations for every 2 orbits around the Sun.
4. Atmosphere and Magnetic Field
- Exosphere Composition:
- Contains traces of oxygen, sodium, and hydrogen.
- Created by solar wind and micrometeorite impacts.
- Weak Magnetic Field: ~1% of Earth’s magnetic strength.
- Suggests a partially molten core.
5. Surface and Geological Features
- Surface Resembles the Moon:
- Covered in impact craters.
- Caloris Basin: One of the largest impact craters (1,550 km wide).
- Scarps (Cliffs): Evidence of planetary shrinking as Mercury’s core cools.
- Plains: Smooth plains likely formed by ancient volcanic activity.
6. Temperature Extremes
- Daytime: Extremely hot due to proximity to the Sun.
- Nighttime: Frigid, as Mercury lacks a thick atmosphere to retain heat.
- Temperature Variation: Greatest in the solar system.
7. Exploration of Mercury
- Mariner 10 (1974-75): First spacecraft to visit Mercury (three flybys).
- MESSENGER (2011-2015): Orbited Mercury, mapping 100% of the surface.
- BepiColombo (2025 Arrival): Joint ESA-JAXA mission currently en route.
8. Interesting Facts
- Mythology: Named after Mercury, the Roman messenger god (Greek: Hermes).
- Fastest Planet: Completes an orbit faster than any other planet.
- Double Sunrises: At certain points in its orbit, the Sun appears to rise, set, and rise again.
- No Moons/Rings: Mercury is one of only two planets (along with Venus) with no moons or rings.
9. Why is Mercury Important?
- Understanding Planet Formation: Studying Mercury helps scientists understand how rocky planets form.
- Unique Core: Its large iron core provides clues about the solar system’s early history.
- Extreme Environment: Helps study the effects of solar radiation on planetary surfaces.
10. Key Measurements
| Property | Value |
|---|---|
| Diameter | 4,880 km |
| Distance from Sun | 57.9 million km (0.39 AU) |
| Orbital Period | 88 Earth days |
| Rotation Period | 59 Earth days |
| Gravity | 3.7 m/s² |
| Surface Temperature | -180°C to 430°C |
| Moons | 0 |
| Magnetic Field | Weak (1% of Earth’s) |