If God made the formation of biological molecules and the formation of life something that was probable on Earth due to simple chemistry, then it is quite likely that life formed elsewhere in the UNCOMPREHENDINGLY VAST universe. This in no way means that God didn't create life in ALL places, or that it was not part of God's plan.
Also one might conclude that it was evidence for abiogenesis on Mars, which would be evidence that abiogenesis on Earth is probable. Evidence isn't “proof”. And it wouldn't be evidence against God (let alone ‘disproof of God); just the notion that God created life ONLY on Earth.
After all, didn't the Mormon God already make life on other planets (AFAIK)?
I take exemption with that as I believe it is the same God, we just worship him differently.
That said however you are correct. From Moses 1 found in the Pearl of Great Price:
33 And worlds without number have I created; and I also created them for mine own purpose; and by the Son I created them, which is mine Only Begotten.
34 And the first man of all men have I called Adam, which is many.
35 But only an account of this earth, and the inhabitants thereof, give I unto you. For behold, there are many worlds that have passed away by the word of my power. And there are many that now stand, and innumerable are they unto man; but all things are numbered unto me, for they are mine and I know them.
So God through Jesus created worlds without number, and only gave us an account of the creation of Earth. Kind of a need to know, as someone mentioned earlier.