... D rad Bacteria: Candidate Astronauts . ... These bacteria could survive on another planet. ... The graceful spiral structure seen in this computer visualization does not portray winding spiral arms in a distant galaxy of stars. ... Watching from a hillside near Austin, Texas, planet Earth, astrophotographer Russell Croman recorded this view of their passing as clouds gracefully dimmed the brilliant moonlight. To Fly Free in Space . ... Shadows of these clouds can even be seen on lower cloud decks. ...