Rumors and mobile computing -- there's no escaping them. You can't escape Apple (NASDAQ:AAPL) iPhone 5S or iPhone 6 rumors, touting this or that feature, or guesstimating a rollout date. Not to be outdone, Nokia (NYSE:NOK) started a major buzz with a recent Facebook post showing its Lumia phone with an intriguing little gadget on the back aimed at the sun -- almost as if it were outfitted with solar charging capabilities. And Nokia's post accompanying the picture added to the intrigue.

Basis for the rumors

Investing in any company based solely on gossip is a scary proposition. But some industry rumors carry more weight than others, and Nokia's Facebook picture and associated text of its Lumia phone is one of those instances. Why? For one thing, this isn't the first time Nokia's been linked to a solar-power-charging feature for its smartphones.

The solar-powered Nokia smartphone rumors began last month, with news that privately owned Sunpartner Group was touting an intriguing technology that allows a surface -- like a smartphone's cover, say -- to produce power from sun or artificial light. Then a Microsoft-related site, MonWindowsPhone, learned that Sunpartner had signed a deal with an "unnamed" smartphone manufacturer. Nokia was promptly anointed the unnamed manufacturer, and the solar-powered smartphone scuttlebutt was up and running.

No. 2, and even more telling than earlier rumors, is the Nokia Facebook post itself. In addition to the picture, the post says, "Sun, sun, sun, here we come!" Are the picture and post simply Nokia's ode to summer? Possibly, but a quick scan through the hundreds of comments suggest that a lot of Nokia followers came to the same conclusion I did: Nokia's close to solving the problem of the short-lived batteries that provide smartphone owners' biggest gripe.

It's hard to imagine that Nokia didn't realize the reaction it'd get when it posted a photo of the sun-drenched Lumia. Assuming Nokia knew what Facebook followers would surmise from the post, there's absolutely nothing to gain, and a lot to lose, if it turns out there's nothing in the works to back it up. Maybe Nokia will use Sunpartner Group's solar-charging solution, or possibly an in-house alternative. But it had better have something solar-related up its sleeve, or there will be a lot of disappointed Lumia users. Either that, or CEO Stephen Elop needs to explain to shareholders the solar "misunderstanding," if that's what it turns out to be, in a hurry.

Innovation isn't new

Nokia already has a groundbreaking smartphone camera, wireless charging, top-flight mapping capabilities, and runs what was recently voted the top mobile OS by readers of PC Magazine -- Microsoft’s (NASDAQ:MSFT) Windows 8. Apple's iOS and Google's (NASDAQ:GOOGL) Android together control about 90% of the world's smartphone market, thanks in large part to Samsung’s ties to Google, but are second and third, respectively, on PC Magazine OS "best of" list. On a scale of 1 to 10, Windows 8 was the only system to register a 9 in the PC Magazine survey: Apple followed with an 8.6, and Google's Android users rated it 8.1.

To top it off, 88% of Windows 8 users chose their smartphone based on its OS. As Nokia is one of Microsoft's key phone partners, the PC Magazine results are a feather in Nokia's cap, too. Now, add what would be an immediate game-changer -- solar charging capabilities built directly into the phone -- and the momentum Nokia's gained from its 4.4 million Lumia units sold in Q4 would really get a boost.

There's still not enough tangible evidence to pull the investment trigger on Nokia, based solely on this latest speculation. But there's no doubt a smartphone with a solar-powered charging feature would change the playing field, and someone's going to bring it to market. Why not Nokia?

Should a Nokia-inspired, solar-powered smartphone alternative come to pass -- and rumors suggest it could be later this year -- the 4.4 million Lumia's sold in Q4 would pale in comparison. In the world of smartphones, each new device iteration seems little more than an improvement on existing technologies or features. But solar battery charging -- that'll be the first real game-changer in a long while. If Nokia introduces a solar smartphone ahead of its rivals, shareholders are going to enjoy a nice ride.