Mercury's magnetic field
... that data from Mariner 10 led to the discovery of Mercury's magnetic field in 1974?
... that data from <a href="./Mariner_10" id="mwAmA" rel="mw:WikiLink" title="Mariner 10">Mariner 10</a> <i id="mwAmE">(pictured)</i> led to the discovery of <b id="mwAmI"><a href="./Mercury's_magnetic_field" id="mwAmM" rel="mw:WikiLink" title="Mercury's magnetic field">Mercury's magnetic field</a></b> in 1974?