Guide to Space
Valles Marineris: The Grandest Canyon of All
A digital terrain model of a portion of Mars' Valles Marineris, the largest canyon in the Solar System. Credit: ESA/DLR/FU…
Why Planets Orbit the Sun
[/caption] In ancient times, astronomers thought that all celestial objects - the Sun, Moon, planets and stars - orbited around…
Pictures of the Moon
The Moon is one of the most familiar and beautiful objects in the night sky (and daytime too!). Let's take…
Characteristics of Mercury
[/caption] Quick Mercury Stats Mass: 0.3302 x 1024 kg Volume: 6.083 x 1010 km3 Average radius: 2439.7 km Average diameter:…
Does The Sun Rotate?
The rotation of the Sun is kind of hard to pin down. That's because a day on the Sun depends…
Who Discovered Mercury?
[/caption] Mercury is one of the 5 planets visible with the unaided eye. Even thousands of years ago, ancient astronomers…
Atmosphere of Mercury
[/caption] When you look at an image of Mercury, it looks like a dry, airless world. But you might be…
The Rings of Neptune
Neptune is one of four planets in our Solar System with planetary rings. Neptune was not discovered until 1846 and…
Who Discovered Neptune?
Five of the planets in the night sky are easy to see with the unaided eye, and have been known…
How Did Neptune Get Its Name?
How did Neptune get its name? Shortly after its discovery, Neptune was only referred to as "the planet exterior to…