Kevin Gill from Los Angeles, CA, United States, CC BY 2.0Mars
The red desert world that once had rivers, lakes and perhaps a northern ocean
Overview
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", for its orange-red appearance. Mars is a desert-like rocky planet with a tenuous atmosphere that is primarily carbon dioxide. At the average surface level the atmospheric pressure is a few thousandths of Earth's, atmospheric temperature ranges from −153 to 20 °C, and cosmic radiation is high. Mars retains some water, in the ground as well as thinly in the atmosphere, forming cirrus clouds, fog, frost, larger polar regions of permafrost and ice caps, but no bodies of liquid surface water. Its surface gravity is roughly a third of Earth's or double that of the Moon. Its mean diameter, 6,779 km (4,212 mi), is about half the Earth's, or twice the Moon's, and its surface area is around the size of all the dry land of Earth.
Source: Wikipedia
Why it matters
- Home to Olympus Mons, the tallest volcano in the Solar System, and Valles Marineris, a canyon as long as the USA is wide.
- Rovers and orbiters have found ancient river deltas, lake beds and clay minerals that formed in liquid water.
- Thin CO2 atmosphere (less than 1% of Earth's pressure) and seasonal polar caps of water and dry ice.
System
- Discovered
- known since antiquity
- Star
- Sun · G2 V · 5,772 K · 1 M☉
- System
- 8 known planets
Orbit in the Solar System
| World | Period | Distance | Radius | Mass | Temp. |
|---|---|---|---|---|---|
| Mercury | 88 d | 0.387 AU | 0.38 R⊕ | 0.055 M⊕ | 440 K |
| Venus | 224.7 d | 0.723 AU | 0.95 R⊕ | 0.82 M⊕ | 737 K |
| Earth | 365.2 d | 1 AU | 1 R⊕ | 1 M⊕ | 288 K |
| Mars | 687 d | 1.52 AU | 0.53 R⊕ | 0.11 M⊕ | 208 K |
| Ceres | 4.6 yr | 2.77 AU | 0.07 R⊕ | 0.94 ×10²¹ kg | — |
| Jupiter | 11.9 yr | 5.2 AU | 1 R♃ | 1 M♃ | 163 K |
| Saturn | 29.4 yr | 9.57 AU | 0.84 R♃ | 95.11 M⊕ | 133 K |
| Uranus | 83.7 yr | 19.16 AU | 0.36 R♃ | 14.53 M⊕ | 78 K |
| Neptune | 163.7 yr | 30.18 AU | 3.88 R⊕ | 17.08 M⊕ | 73 K |
| Pluto | 247.9 yr | 39.48 AU | 0.19 R⊕ | 13 ×10²¹ kg | 48 K |
| Haumea | 282 yr | 43.1 AU | 0.12 R⊕ | — | 50 K |
| Makemake | 306.6 yr | 45.6 AU | 0.11 R⊕ | 3.1 ×10²¹ kg | — |
| Eris | 561.3 yr | 67.9 AU | 0.18 R⊕ | 17 ×10²¹ kg | 43 K |
| Sedna | 12,676.2 yr | 544 AU | 0.08 R⊕ | — | 12 K |
By the numbers
- Radius
- 0.53 R⊕3,393 km
- Mass
- 0.11 M⊕0.64 ×10²⁴ kg
- Orbital period
- 687 d1.88 yr
- Distance from Sun
- 1.52 AU228 million km
- Eccentricity
- 0.094elliptical
- Mean temperature
- -65 °C208 K
- Gravity
- 3.7 m/s²0.38 g
- Day length
- 24.7 h1 Earth days
- Moons
- 2
- Density
- 3.93 g/cm³
- Axial tilt
- 25.2°
Sources
Image: Kevin Gill from Los Angeles, CA, United States, CC BY 2.0 · CC BY 2.0 · image page
Text: Wikipedia (CC BY-SA 4.0). Taglines and highlights are editorial.