“The last time we posted anything was at the end of January, and it was just confirmation that some results from a year ago had been validated,” he said.

The seventh of 10 items in the January update refers to a study, by Chris Mason of Weill Cornell Medicine, on the “genetic, epigenetic, and transcriptional dynamics of each twin.” The update was prepared because some NASA scientists were going to a conference to discuss results, Mr. Humphries said.

“Although 93% of genes’ expression returned to normal postflight, a subset of several hundred ‘space genes’ were still disrupted after return to Earth,” the update read.

That fact seemed to get twisted in popular press coverage. For example, CNN initially wrote that spending a year in space “transforms your genes” before updating on Thursday to say it “transforms your gene expression.” After substantially rewriting the story — the old version can still be read here — it said the story had been “updated with additional information from NASA.”

Some outlets, including Ars Technica, The Verge and National Geographic, spotted and combated the misinformation that had been spreading. But even the astronauts themselves were snookered.