Tracking the strength of mobile operating platforms occupies the time of more than one analysis firm in the mobile sphere, but the numbers always tell a compelling story: mostly, that Google’s Android and Apple’s iOS are really, really popular, and that means tough times for competitors.

The latest look at the division of smartphone market share, coming from comScore and posted by TechCrunch, suggests that Android remains a juggernaut and is continuing to grow faster than any other mobile operating system. comScore puts Android software on 42 percent of the total U.S. smartphone market in July, with an increase of 5.4 percent from April and 1.7 from June. Up next is Apple, with 27 percent of the market and a slower increase of 1 percent from April and 0.4 percent from June. Together, the two systems account for better than two-thirds of all smartphones on the market.

Meanwhile, Research In Motion’s BlackBerry, Microsoft’s Windows Phone 7 and Nokia’s Symbian all continue to lose ground to the two powerhouse operating systems. BlackBerry fell 4 percentage points from April to 21.7 percent, while Microsoft declined by 1 percentage point to 5.7 percent. Symbian holds 1.9 percent.

This is more of the same as far as the mobile market. Nokia has already said it’s discontinuing Symbian as it goes into business with Windows Phone 7 as the operating system of choice for its handsets, and RIM has been losing market share basically since Android and iOS were invented. BlackBerry can’t seem to find a way to combat the two new operating systems – Apple offers more apps and an easier to use system, while Android’s open nature and wide variety of handsets and carriers allows it to be just about everywhere.

Windows Phone 7 had previously made up some ground against its competitors, but it still struggles with basic visibility. The number of Windows Phone 7 phones is somewhat limited, and while Microsoft continues to push a gaming angle with its devices, it doesn’t seem to have quite the product perks to make it stand above Android and iOS. But with major shake-ups at both companies recently with Google’s acquisition of Motorola Mobility and the departure of Apple CEO Steve Jobs, Microsoft may have an opportunity to break out.

It seems that, left (more or less) unchecked, Android and iOS are going to continue to pick away at their smaller competitors. The major switch of Verizon Wireless and AT&T toward 4G LTE in the next year or two will also likely bolster Android’s position as carriers add more and more faster devices. And if analyst firm NPD is right, the Motorola acquisition could mean even more positive gains for Google in the future.