Google gave two computer scientists access to more than a million of its mobile search records in research aimed at understanding the unique needs of wireless Web surfers. Judging by the results, what users really need is a porn portal, as more searches were for smut than anything else.

The research was first reported in the New Scientist last weekend, but it didn’t go into much detail. The full paper (PDF, or Google cache if you prefer HTML) was published earlier this month and has some interesting material based on a random sample of searches made through an unspecified U.S. carrier (Sprint or Cingular) in 2005. Among the highlights:

• More than 20% of Google searches from cell phones are for “Adult” content, whereas the comparable figure for PDAs is less than 5%. The researchers believe this is because PDAs are used more for business, phones for entertainment.

• Most users leave the Google site after performing a search. But porn searchers are noticeably more likely than others to stick around (and search for more porn).

• The text input system on cell phones is so bad that each search takes a whole minute. Most of that time is spent entering the query term through a numeric keypad.

The scientists compare their figures with a 2002 study published in IEEE Computer (again, PDF or Google cache). Using data from the Excite search engine, this found that “Adult” queries fell from 17% in 1997 to 8% in 2001.

More recent figures for desktop searches are hard to find, but Larry Page’s comments in a Time hagiography last week suggest that not much has changed since the Excite days. He claimed that only a “single-digit” percentage of Google users searched for porn. (Google itself doesn’t publish much data, except for the heavily edited Zeitgeist lists.)

The proportion of mobile users performing “Adult” queries could also fall as (and if) the wireless Web goes from a geek toy to something more mainstream. The researchers actually mention this in the paper, and I think they’re right. Pornography often drives technology. The wireless Web is just the latest example.

Google probably won’t actually launch a mobile porn portal. It’s already fighting two high-profile lawsuits over the issue: The White House wants to use the easy availability of porn on search engines to justify online censorship and mandatory government tracking of Internet users, while a porn site says Google's thumbnail images harm its mobile market.

The business may not be particularly profitable anyway. Google makes only a few cents per click from porn ads, compared to more than $10 from real estate brokers in some cities, and $50 (yes, fifty bucks a click!) from sites selling cell phone records.

More likely, Google will try to encourage other uses for the wireless Web. Maps are the real killer apps. They’re already the most popular use for home broadband connections, and they have obvious appeal to people moving around. Google, Yahoo, and Microsoft just need to get their new mapping apps working on mobile devices, though that could take a hardware upgrade.