1. By: Sharon Paramby Shybu
Age: 11
School : Sunrise English Private School
Inner Planets
In our Solar System, astronomers often divide the planets into two groups — the inner
planets and the outer planets. The inner planets are closer to the Sun and are smaller
and rockier. The outer planets are further away, larger and made up mostly of gas. The
inner planets are Mercury, Venus, Earth and Mars.
Mercury
Mercury is the smallest planet in our Solar System and also the closest. It rotates slowly
(59 Earth days) relative to the time it takes to rotate around the sun (88 days). The planet
has no moons, but has a tenuous atmosphere (exosphere) containing oxygen, sodium,
hydrogen, helium and potassium.
Venus
Venus was once considered a twin planet to Earth, until astronomers discovered its
surface is at a lead-melting temperature of 900 degrees Fahrenheit (480 degrees
Celsius). The planet is also a slow rotator, with a 243-day long Venusian day and an orbit
around the sun at 225 days. Its atmosphere is thick and contains carbon dioxide and
nitrogen. The planet has no rings or moons and is currently being visited by the European
Space Agency’s Venus Express spacecraft.
Earth
Earth is the only planet with life as we know it, but astronomers have found some nearly
Earth-sized planets outside of our solar system in what could be habitable regions of their
respective stars. It contains an atmosphere of nitrogen and oxygen, and has one moon
and no rings. Many spacecraft circle our planet to provide telecommunications, weather
information and other services.
Mars
Mars is a planet under intense study because it shows signs of liquid water flowing on its
surface in the ancient past. Today, however, its atmosphere is a wispy mix of carbon
dioxide, nitrogen and argon. It has two tiny moons (Phobos and Deimos) and no rings. A
Mars day is slightly longer than 24 Earth hours and it takes the planet about 687 Earth
days to circle the Sun. There’s a small fleet of orbiters and rovers at Mars right now,
including the large NASA Curiosity rover that landed in 2012.
