Clones and bootlegs
There have been many unofficial ports of Asteroids produced. These include near-copies such as Acornsoft's Meteors and Ambrosia Software's Maelstrom, as well as those with expanded gameplay and background, such as Asterax, Astrogeddon, Stardust, Spheres of Chaos and Astro Fire. The Vectrex had a built-in similar game called "Minestorm". Even on the Sony PSP, homebrew Asteroids were made on that platform when hacked.
i've played a ton of astroids clones; some of them commercial. i think you're fine. take a look at this asteroids clone:
it's for the xblig, clearly inspired by astroids, yet atari never did anything
that said, it all depends on how similar it is and how high-profile it is, and whether you actually include the word "asteroids" in your name, and other such factors. i can only see atari caring at all if your game hits the top 10 on iphone, has "asteroids" in the title, and isn't so much "inspired" by asteroids as actually a clone of it (with very little added or changed). otherwise it's fine
i also agree that the game is very "my first game". for example, use your browser's zoom function, and notice that the gui no longer matches up with the game. it looks like it's made up of clip-art and clip-sounds
i mean for serious, compare that echoes game to yours; why would anyone play your game over that? and that game's from 2006, and isn't even itself very impressive
and you have to realize we aren't trying to be mean, we're just tired of seeing games with very little work trying to be sold commercially. the time to sell commercial games is after you make games that impress other game developers and have an established audience, after your games are so popular as freeware that the fans are saying 'you should go commercial!', not when you're first starting out and are learning. making indie games isn't a get rich quick scheme, it's something you should care about and put years of time and effort into