Ricardo Garay 
Little Guardians Series — Hunt for the Planets 

This series of little alien guardians of nature that come out of your planet in pursuit of the biggest polluter of the universe, the wicked Zirt Zlunder. He escapes and comes to stop on Earth. In this book, Zirt Zlunder disappears. The Little Guardians must locate Zirt Zlunder, but this time the hunt will be off planet Earth. They will have to travel all the planets of our solar system. And in this adventure will be attacked by Zirt Zlunder. They will be able to arrest Zirt Zlunder the terrible polluter?