Mercury's Strange Hollows "These hollows were a major surprise,"
says David Blewett, science team member from the Johns Hopkins
University Applied Physics Laboratory. "We've been thinking of
Mercury as a relic – a place that's really not changing much
anymore, except by impact cratering. But the hollows appear to
be younger than the craters in which they are found, and that
means Mercury's surface is still evolving in a surprising way."
Mars Reconnaissance Orbiter spotted similar depressions in the
carbon dioxide ice at Mars' south pole, giving that surface a
"swiss cheese" appearance. But on Mercury they're found in rock
and often have bright interiors and halos. "We've never seen
anything quite like this on a rocky surface." If you could stand
in one of these "sleepy" hollows on Mercury's surface, you'd
find yourself, like Ichabod Crane, in a quiet, still, haunting
place, with a black sky above your head. "There's essentially no
atmosphere on Mercury," explains Blewett. "And with no
atmosphere, wind doesn't