Scientists think the magnesium, and possibly other metals not yet detected, comes from cosmic dust left by passing comets. (sciencenews.org)
Signal, too, remains a cold case file, though Antonio Paris of St. Petersburg College in Florida now theorizes that it might have come from a pair of passing comets and their attendant hydrogen clouds. (discovermagazine.com)
They calculate that Planet X is several times larger than Jupiter, which would give it a gravitational field powerful enough to snare passing comets and fling them sunward in a narrow swath. (discovermagazine.com)