With its Firefox browser rapidly losing share, and its financial ties to Google finished, the Mozilla Foundation finds itself facing the most pivotal moment in its history since its founding more than a decade ago.

“We’re utterly confident in our stability and viability going forward,” Mozilla chairwoman Mitchell Baker said in a recent interview with Stephen Shankland of Cnet.

But just because the foundation can continue, does that mean it should? 

I think there is still an essential role on the web for a non-profit organization that can develop services that may not generate big profits, but where it would be valuable to have a more neutral player.

But at the same time, at this moment, it’s difficult to say what Mozilla is doing that is so essential to the world.

This is not an easy thing to say. It feels almost ungrateful to question the existence of Mozilla. Without a doubt, the good people who work at Mozilla, and the numerous volunteers who support it, do so because they believe they are part of a larger crusade. And we, as users of the web, owe the foundation our deepest gratitude.

A decade ago, Mozilla launched the Firefox web browser. It would turn out to be one of the defining moments of the web’s evolution.

At the time, Microsoft’s Explorer had thoroughly crushed Netscape. Mozilla built its browser on the rubble of Netscape to offer an alternative to Microsoft — at a time when it didn’t make a shred of financial sense for a profit-based company to make that kind of investment.

Along the way, Mozilla got substantial help from Google, and vice versa. Google signed a partnership that made it the default search engine on Firefox, sending waves of traffic its way while funneling money back to Mozilla. That cash allowed Mozilla to make, for a time, the most innovative and advanced browser.

But even as Google was essentially underwriting the Mozilla Foundation, the search giant launched its own browser, Google Chrome, in 2008. Google initially insisted that Chrome was not really a competitor to Firefox. But Chrome did compete, and eventually surpassed Firefox in terms of browser market share.

In January 2010, Microsoft’s Explorer still had 50.4 percent share, Firefox had 32.7 percent, and Chrome had 6.3 percent. Now, Chrome has 40.8 percent, Explorer has 17.9 percent, Firefox has 16.0 percent, and Apple’s Safari has 15.2 percent.

In all likelihood, given these trends, Firefox will soon fall to the fourth position among browsers sometime within the next year. In that context, the announcement that Yahoo is replacing Google as the default search engine on Firefox seems inevitable. Google doesn’t really need Firefox at this point.

Mozilla, on the other hand, got 90 percent of its revenues from Google, according to its annual report released last month. (You can read a detailed breakdown by VentureBeat’s Emil Protalinski here.)

Given Yahoo’s smaller share in search, and Firefox’s decline in browser share in recent years, it’s hard to imagine how the Yahoo deal (and other search deals Mozilla hopes to strike) will replace that 90 percent.

In the coming year, with its falling browser share and smaller search partner, Mozilla would seem to be facing a big financial hit. But Mozilla has always boasted of having a higher calling, a mission beyond money.

Mozilla defines that mission like this:

“The Mozilla project works to bring independence and choice to the Web so that everyone who uses it recognizes they possess the agency to shape it. We build communities of citizens who are passionate about the opportunities of a free and open Web, and who have the skills and know how to take control of their online experiences. We build products that showcase the vast capabilities of the Web and enrich people’s lives. Our mission is to keep the Internet accessible, so people worldwide can go beyond being users of the Web to also become creators and citizens of the Web.”

A grand statement. But in a practical sense, what does that mean? Continuing to plug away on new features for the world’s number four browser doesn’t seem to be a worthy enough goal.

Of course, Mozilla does make a host of other, smaller applications. And it’s done some work close to my heart: Partnering with journalists and media organizations to focus on innovative news services and applications. Good stuff, but smaller in scope.

If there is a new emerging core project, it appears to be Mozilla’s attempt to build an open mobile platform, Firefox OS, to offer an alternative to Apple’s iOS and Google’s Android. The foundation argues that Android and iOS are closed systems that force you to choose an ecosystem for your entertainment and app purchases as well as web services and personal data.

“What iOS and Android have in common is they’re jails. They are very shiny, but once you join these ecosystems, you’re really caught in them,” Andreas Gal, Mozilla’s chief technology officer, said to Shankland.

I’m not so sure, though. The people in Apple’s jail are pretty content to stay in Apple’s jail. And I think Google would argue that with Android, it’s already making a more open mobile OS to compete with Apple’s iOS. And given that there are some deep-pocketed corporations such as Microsoft trying to create a third alternative (and not getting a ton of traction), it seems unlikely that Mozilla can make the case it has a more compelling alternative.

So, I’m not buying that a mobile OS is really Mozilla’s big mission. But there are other roles I think it could play, places where a non-profit might lead the charge because for-profit companies might not be attracted.

I’d like to see better open alternatives for my online identity (like Mozilla Persona), a truly open social network, and truly open cloud services (an expanded role of Mozilla Cloud services or perhaps a merger of sorts with ownCloud?). Perhaps even an open RSS news reader to replace the shuttered Google Reader.

The people at Mozilla are super smart. They’ve probably discussed and maybe discarded all of these ideas as too impractical, too expensive, or just plain unnecessary. Or maybe they’re already cooking up something amazing.

But if Mozilla is going to soldier on for another decade, then I suspect that it will have to lean even harder on donors and other foundations. And to attract those donations, Mozilla needs to be able to articulate its mission in the simplest of terms.

It needs to be able to tell us the story of why the web still needs Mozilla.