Just what sort of future Energy Resources of Australia has is a question that is increasingly weighing on the minds of mining equity analysts.

The Rio Tinto-controlled uranium producer is going through a sticky patch, with heavy rains forcing a temporary halt to mining at its Ranger site in the Northern Territory.

But it's the longer-term outlook that is of more concern, particularly ERA's reluctance to sanction exploration that would pave the way for an underground mine. Without the Deeps project, which would access 34,000 tonnes of uranium oxide, ERA looks to be in decline.

The Ranger pit is set to be exhausted by 2012 and the $250 million heap leach project, which would allow the processing of lower-grade material, would only offer a temporary respite.

UBS's theory is that while ERA's board could sign off on Deeps tomorrow, it won't go ahead without the support of the traditional owners.

The Gundjeihmi Aboriginal Corporation, representing the Mirarr people, opposes the heap leach and the Deeps projects. It is using ERA's water management woes to bolster its case.

Unlike the nearby Jabiluka deposit, approval from the Mirarr isn't needed to go ahead with the Deeps project, which is on the existing Ranger mining lease.

But proceeding without their approval would not sit well with Rio's social responsibility ethic, nor would the sale of its 68 per cent stake to another party that wouldn't have such scruples.

Barring any breakthrough, it all points to a gradual rundown at ERA until the Ranger lease expires in 2021.

If so, it's not the end of the world for Rio, which got the ERA stake through its 2000 takeover of North, and which UBS points out has yielded fantastic returns.

Other investors, already suffering from a halving in ERA's share price over the past year, might think differently.

It's no wonder Rio is keener on uranium in Namibia, where it is talking to Extract Resources about developing its Husab project via Rio's Rossing mine.