The Microsoft-Nokia deal to put Windows Phone 7 on millions of cell phones gives both companies a chance to carve into the mobile market. The deal could also save them down the road by opening a crucial avenue to growth.

While it may seem Microsoft, with $6.63 billion second quarter net income, doesn’t need to be saved, the fact is most of that money came from old technologies, like Office and server software; not exactly high growth. Nokia, which once boasted a 50% share of the mobile phone market, has slipped to 29%. That is still a substantial chunk of the business, but Google is reportedly activating over a quarter-million Android devices daily.

Both companies would survive without the deal, but growth is essential to attract the brightest designers and engineers. This partnership paves the way for Microsoft and Nokia to keep pace with the other players in the mobile universe.