Could you please repeat that? http://hdxvideos.site/ video x This isn't the first time that NASA has measured the concentration of gases in the Martian atmosphere. "There was really groundbreaking work back in the '70s with the Viking landers," Paul Mahaffy, the lead author behind one of the papers and a NASA scientist, told ABC News. "But those landers were a more primitive version of the thing that's landed on Mars now."