CREATING A PIECE OF MIDDLE EARTH
Seismic imaging can generate maps of
the mantle, but geologists are not going
to collect direct samples of those parts
of the planet anytime soon. So some
researchers are exploring the earth’s
deep interior by re-creating it in the laboratory. Last year, Stanford mineral physicist Wendy Mao simulated conditions in
the upper mantle using a technique that
could test theories about the formation
of the earth’s core. She subjected a
cell-size mixture of iron-rich alloy and
silicate to 60,000 times the atmospheric
pressure at sea level. Then she heated
the sample to 1800°C and peered inside
it with a series of X-rays to produce the
three-dimensional image shown at left.
Mao observed that the iron melted into
discrete spheres, visible here as bright
circles in the darker silicate matrix. In
future simulations she plans to crank up
both temperature and pressure to find
out if iron could have melted and trickled
through the silicate mantle to give rise to
the core some 4 billion years ago. An iron
and silicate meteorite, below, is thought
to resemble the raw material from which
the core formed. “But in the lab,” Mao
says, “we can get a real window into the
earth’s interior.”
