But what happens when one of these streams approaches a planet such
as Earth? Prézeau used computer simulations to find out.

His analysis found that when a dark matter stream goes through a
planet, the stream particles focus into an ultra-dense filament, or
“hair,” of dark matter. In fact, there should be many such hairs
sprouting from Earth.

A stream of ordinary matter would not go through Earth and out the
other side. But from the point of view of dark matter, Earth is no
obstacle. According to Prézeau’s simulations, Earth’s gravity would
focus and bend the stream of dark matter particles into a narrow
dense hair.

Hairs emerging from planets have both “roots,” the densest
concentration of dark matter particles in the hair, and “tips,”
where the hair ends. When particles of a dark matter stream pass
through Earth’s core, they focus at the “root” of a hair, where the
density of the particles is about a billion times more than average.
The root of such a hair should be around 600,000 miles (1 million
kilometers) away from the surface, or twice as far as the Moon. The
stream particles that graze Earth’s surface will form the tip of the
hair, about twice as far from Earth as the hair’s root.

Another fascinating finding from these computer simulations is that
the changes in density found inside our planet — from the inner core,
to the outer core, to the mantle to the crust — would be reflected in
the hairs. The hairs would have “kinks” in them that correspond to
the transitions between the different layers of Earth. Theoretically,
if it were possible to obtain this information, scientists could use
hairs of cold dark matter to map out the layers of any planetary
body, and even infer the depths of oceans on icy moons.

Earth might have hairy dark matter | Astronomy.com
http://www.astronomy.com/news/2015/1...ry-dark-matter