The meteor hypothesis, Dr. Walker said in a telephone interview, remains to be spelled out in terms of ''good, hard mathematics and meteorological physics.'' He is now assessing such admittedly far-out proposals as explosion of a tanker laden with liquid hydrogen, which might not produce a very bright flash.

There is no maritime record of such an explosion but a weather report sent by a 600-foot Japanese vessel, Dairin Maru, indicates that it was less than 50 miles from the site. Dr. Walker said yesterday he is trying to contact the ship and find out if anything was seen. He has also asked the Japanese weather service for information on thickness of the clock deck, which extended across Japan to see if it was sufficient to hide a flash from aircraft overhead.

Crucial Implications

Co-authors of his report in Science were Charles S. McCreery and Firmin J. Oliveira. Their institute is at the University of Hawaii in Manoa. Among the records that they examined were those from an array of 11 hydrophones near Wake Island. They apparently recorded volcanic rumbling from underwater eruptions at Kaitoku Seamount 910 miles south of the cloud sighting, but nothing near that site.

Any volcanic plume from Kaitoku Seamount should have been blown in the opposite direction, the group concluded.

''Needless to say,'' Dr. Walker recently wrote to a Dutch colleague, ''it is important for the mystery to be solved. One should consider whether a nuclear war would have been started if the cloud had been observed in a more populated area.''

Two Previous Mysteries

The same fears have been expressed, should there be a recurrence of the great 1908 explosion. It leveled forests over a large part of Siberia, starting fires and killing numerous reindeer. Presumably it occurred high in the air, for no crater was formed.

The favored explanation is that it was a comet too insubstantial to survive passage through the atmosphere, but moving so fast it exploded from the resulting heat.