AP PHOTO/NASA/HUBBLE
Voices
revised the game plan.
Consider Mars — a poster child
for geophysical inactivity, or so it
was thought. The Red Planet has
long been assumed to be as inert
as medieval peasantry, but closer examination shows that it’s
less torpid than believed. Orbiters have photographed features
known as “dark slope streaks”
extending down the sides of crater and canyon walls. These sinewy stains are about the width of
your living room, and grow longer as the sun and summer raise
the surface temperature. They
SETH
SHOSTAK
sometimes extend a half mile
or more, and come and go with
the seasons. The obvious — and
most plausible — explanation is
that these streaks are caused by
mineral-laden ice just under the
surface, melting in the warmth.
It wets the landscape as it runs
downhill.
Mind you, the idea that these
streaks are salty water (which
helpfully has a lower freezing point
than pure water) is based on circumstantial evidence only. Pictures, in other words. But if true,
it suggests that the quickest way
to find Martians might be to land a
rover on the streaks, scoop up the
wet dirt, and check for microbes
HUFFINGTON
12.22.13
In this Hubble
Space
Telescope
image,
Jupiter’s
moon
Ganymede
is shown
just before it
ducks behind
the giant
planet. Many
researchers
believe that
Jupiter’s
moons are
more likely
than Mars to
hold the title
of “nearest
rock with life.”