Professor Astro Cat's Solar System is a fun app for elementary age kids to learn about the solar system. Kids swipe to go from planet to planet and explore the solar system. For each planet, there are interesting facts, and you can unzip the planet to see inside.
Well-done animations and snappy interactivity contribute to the exploration. My favorite was an animation demonstrating that "The volume of Jupiter is so great you could fit over 1,300 Earths inside it." When you tap on Jupiter, it explodes into 1300 tiny earths that bounce around for a while before coming to rest. The music and sound effects are pleasant and contribute to the atmosphere without becoming obnoxious.
After exploring each planet, you can take the JetPack challenge, which consists of a series of 10 questions based on the material. Some of the questions are easy, some even silly, but some are harder and a few require thinking about the material, and not just memorization. Succeed on the challenge and you earn not only a medal, but parts towards building a spaceship. If you don't succeed on the challenge, you can take it as many times as you want. Earn all the spaceship parts and you can launch your spaceship!
In addition to the planets, you can also explore space travel. It's mind boggling to me to realize that I remember the moon landing, but for the intended audience for this app, it's ancient history.
I only have two complaints about the app. As you swipe through the solar system, you come to the asteroid belt, but there didn't seem to be any information on the asteroid belt no matter how many times I tapped it. And WHERE IS PLUTO! OK, I know that Pluto was demoted and is no longer a planet, but doesn't it rate at least a mention and a discussion of why it's no longer considered a planet? The Kuiper Belt does appear in the app, but like the Asteroid Belt, you don't seem to be able to tap it to get any information.
Overall, this is a fun and interesting app, and while it's targeted to elementary age children, I learned some things from it!