Solar System/Terrestrial Bodies


 * For general information about the event, see Solar System.

Terrestrial Bodies is the topic of Solar System for the 2018 season. The topic covers the terrestrial planets (excluding Earth), the Earth's Moon, several other rocky moons such as Io, Phobos, and Deimos, and asteroids and comets. The focus of the event is on the history and geology of these bodies.

Mercury
Mercury is the smallest planet with a radius of 2439 km. It is also the planet closest to the sun at a distance of 57.9 million kilometers. Its year is 88 earth days long, and its day is 59 earth days long. The surface gravity of mercury is 1/3 of Earth's, so it cannot hold on to an atmosphere. Therefore its surface is scarred with the craters of meteors that would have broken up if it had an atmosphere. The surface temperatures at day and at night are very different. The temperature during the day is 227°C and the temperature at night is -173°C. Its most noticeable feature is the largest impact crater on its surface, the Caloris basin.

Venus
Venus is the third smallest planet in the solar system with a radius of 6051 km. It is also the second closest to the sun at a distance of 108.2 million kilometers. It is the only planet whose day is longer than its year. Its day is 243 Earth days, and its year is 225 Earth days. The extremely long rotation periods of Venus and Mercury is thought to be caused by mutual gravitation pull; Mercury is sometimes thought to be an escaped moon of Venus. Venus is often called Earth's sister planet because of its close proximity to Earth, and because of its similar diameter and mass. People even thought it could hold life, but sadly people discovered that the greenhouse effect on Venus raised the surface temperature to the highest in the Solar System.

Earth
NOTE: Earth is not included as a major part of the event for 2018; however, a basic knowledge of how Earth fits in the context of the Solar System will likely be of use.

Earth is the third planet from the Sun. It is also the fifth largest at a radius of 6378 km. It is the only planet in the universe known to support intelligent life. We use it as a basis for many measurements of planets and other things in the solar system (ex. the AU (Astronomical Unit), the average distance between the Earth and the Sun, 93,000,000 miles or 149,600,000 km). The year is equal to 365.256 Earth days, and its day is 1 earth day.

Mars
The fourth planet from the Sun at a distance of 227,392,000 km, it's often called the Red Planet due to the large quantities of iron oxide in its soil. The Romans saw it as blood, so they named it for their god of war, Mars. It is the second smallest planet, with a radius of 3397 km. It has a day length of about 25 hours, and a year equal to 687 Earth days. It has been suggested that Mars may hold intelligent life, but it has not been proven. Mars contains two polar ice caps located on the southern and northern ends of the red planet.

30% of the polar ice caps are made up of dry ice or CO2. The dry ice then sublimates creating large gusts sweeping across the polar ice caps creating cirrus clouds in the atmosphere. Mars has two moons, Phobos and Deimos.

Io
Io is the third largest of Jupiter's many moons, and is the most volcanically active body in our solar system