atmosphere of Mercury
...that water vapor is probably present in the tenuous atmosphere of Mercury, being brought to the planet by comets?
...that <a href="./Water_vapor" id="mwDa4" rel="mw:WikiLink" title="Water vapor">water vapor</a> is probably present in the tenuous <b id="mwDa8"><a href="./Atmosphere_of_Mercury" id="mwDbA" rel="mw:WikiLink" title="Atmosphere of Mercury">atmosphere of Mercury</a></b>, being brought to <a href="./Mercury_(planet)" id="mwDbE" rel="mw:WikiLink" title="Mercury (planet)">the planet</a> by <a href="./Comet" id="mwDbI" rel="mw:WikiLink" title="Comet">comets</a>?