Nearly two years since it formally opened for business, the Android Market has hit the 100,000 apps mark, passing a significant milestone for Google's Android mobile operating system. The search giant made the announcement via a simple message on its Android Developer Twitter account: "One hundred thousand apps in Android Market." It's worth noting that this is the official number: third party services that offer unofficial estimates such as AndroLib claim there are 150,000 apps available in the market, but that's inaccurate.

Google is still well behind Apple when it comes to mobile applications, partly due to the fact that Apple launched its app store first in July 2008 while Google arrived on the scene in October 2008. Apple's app store reached 100,000 apps in November 2009 and now iPhone, iPod Touch, and iPad owners have access to over 300,000 iOS apps, at last count. Nevertheless, Android is growing rapidly and continues to solidify its role as the Apple alternative for both developers and consumers.

Last night, before Google made the formal announcement today, The New York Times posted a story noting the milestone and pointing out some of the challenges that remain for Android developers. The article outlined two problems in particular: differences between the hundreds of Android devices on the market as well as payment issues with Google Checkout.