... Mars . ... Curiosity rover provides clues to changes in martian atmosphere . ... Researchers will use SAM repeatedly throughout Curiosity's mission on Mars to check for seasonal changes in atmospheric composition. ... NASAт??s car-sized rover, Curiosity, has taken significant steps toward understanding how Mars may have lost much of its original atmosphere. ... With these initial sniffs of martian atmosphere, SAM also made the most sensitive measurements ever to search for methane gas on Mars. ...