The Inner Planets

The ultimate goal of the game is to plot a path to Neptune. The hidden goal of the game is to give the players, who may not be interested in astronomy, the information that they will need to survive a later episode. This is why the scoring system gives the player 5 points for each planet visited. The planets can be visited in any order as long as the last planet is Neptune. The description of the four inner planets that the game gives are presented here for your more convenient reference.

Mercury. The nearest planet to the sun with an 88 day orbit with a rotation period of almost 59 days meaning that there are only 3 Mercurial days every two years. It is often known as the morning star due to the simple fact that it's greatest angular separation from the sun is only 28.3 degrees so it can only be seen in the early morning or after twilight.

Mercury is the smallest planet in the inner solar system and looks a lot like your moon. It however has a large iron core capable of generating a magnetic field equivalent to 1% of Earth's magnetic field. What is really fascinating about Mercury is how drastic the surface temperature varies. The side facing the sun has a temperature as high as 427C, while the side facing away from the sun is a frigid -183C.

Venus is often referred to as the sister planet to the Earth. This is due to the fact that the planets have a similar size and composition. Venus takes just under 225 days to orbit the sun. It's day, on the other hand, is 243 days which means that there is less than one Venusian day per year.

Venus, however, is closer to the Sun than the Earth and has a thicker atmosphere made up of carbon dioxide with clouds made up of sulphuric acid. This atmosphere, thanks to Carbon's greenhouse properties, makes the surface temperature of Venus a hot 460C which makes it the hottest inner planet even though it is the second planet from the sun.

Earth. You should already be familiar with the third planet from the sun as it is your home world. One of the things you might not be aware of, however, is the fact that the atmosphere of the Earth is mostly nitrogen, with only 21% of the atmosphere being the oxygen that your life depends on.

The Earth's moon is also important to life as it keeps the tilt of the Earth relatively stable. The moon appears to have formed when a protoplanet called Theia crashed into the early Earth. This would be the reason why the moon is composed of the same material as the Earth's crust. The moon is slowly moving further away from the Earth, but don't worry, it is only moving away a few centimeters every year.

Mars. This is the fourth planet from the sun and is often called the red planet due to the color the planet appears to be when observed from Earth. This reddish color is due to the fine iron oxide (rust) dust that covers the planet. Mars does have an atmosphere, but it is really thin compared to Earths. This atmosphere results in martian dust storms. It takes mars almost two years (687 days) with the day being only slightly longer than an Earth day.

The most notable feature of mars has got to be Olympus Mons, which is the largest mountain in the solar system. This mountain has a height of 27 kilometers, which is approximately 3 times greater than mount Everest's 8.8km. Olympus Mons is what is known as a shield volcano, similar to the volcano's that created the Hawaiian islands.

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