A chemical signature in a lunar rock offers new insights into what early oxygen conditions were like on the Moon.

The astronaut who prompted NASA’s first medical evacuation earlier this year said Friday that doctors still don’t know why he suddenly fell sick at the International Space Station. Four-time space flier Mike Fincke said he was eating dinner on Jan. 7 after prepping for a spacewalk the next day when it happened. Fincke, 59, a retired Air Force colonel, said the episode lasted roughly 20 minutes and he felt fine afterward.

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