Potential rivals to Time Inc.'s bid to buy Science 86 magazine, the respected but financially ailing publication owned by the American Association for the Advancement of Science, are emerging -- with assurances that they would keep the award-winning monthly alive.

Both AAAS members and Science 86 staffers fear -- and Time Inc. sources privately confirm -- that the publishing giant would shut down Science 86 and convert its subscribers to Time's own Discover magazine, also a respected but money-losing science publication.

Possible bidders include a group led by Owen Lipstein, a former Science 86 general manager who now owns Mother Earth News magazine and is a general managing partner of American Health magazine.

An earlier bid by Lipstein was deemed inadequate by the AAAS last week, but he is expected to make another bid now that the AAAS apparently has extended its time frame for considering offers. Lipstein, saying "it would be a tragedy for Science 86 to die," declined to comment on his offer.

Similarly, the Economist Group Ltd., which publishes The Economist newsweekly magazine, is exploring a possible bid for the magazine. Economist executives in London could not be reached yesterday.

"I expect that there will be a lot of bids, and the chances of the magazine being saved are improved," said Allen Hammond, Science 86's editor, who confirmed that he and other staffers have been frantically seeking buyers in recent weeks in an effort to keep the magazine from being folded.

There had been confusion as to what the deadline would be for potential suitors to make their bids, with indications that this might be the last week. Apparently, the AAAS will be considering offers for at least another week.

The Time offer -- estimated at approximately $5 million -- remains the top contender, according to sources close to both Time and the AAAS.

But "we don't have a bias on it, one way or the other," said William D. Carey, AAAS' executive director and Science 86's publisher. "I don't know how it's all going to turn out."

With a circulation of more than 739,000, Science 86 is one of the largest publications in the troubled science magazine category, but has lost money in recent years. In fact, Scientific American, Hearst Corp.'s Science Digest and Time's Discover all are losing money. Science 86's losses run in excess of $1 million a year, according to Carey.

"Saving the magazine would be a very difficult thing to do internally without altering its character," he said, indicating that the magazine is likely to be sold.

But selling the magazine to Time Inc., where it is almost certain to be discontinued, might create an "image problem," said one top AAAS official, given the association's not-for-profit, public-interest profile. Consequently, the continuation of Science 86 -- and not just the price tag -- may be a factor in the AAAS' decision to sell.

"Our objective is to do what's best for the association," said Carey, indicating that the decision still will come "soon."