One Tiny Speck For Mankind
NASA's Phoenix Mars Lander has taken the first-ever image of a
single particle of Mars' ubiquitous dust, using its atomic force
microscope.
The particle -- shown at higher magnification than anything ever
seen from another world -- is a rounded particle about one
micrometer, or one millionth of a meter, across. It is a speck of
the dust that cloaks Mars. Such dust particles color the Martian
sky pink, feed storms that regularly envelop the planet and produce
Mars' distinctive red soil.
"This is the first picture of a clay-sized particle on Mars, and
the size agrees with predictions from the colors seen in sunsets on
the Red Planet," said Phoenix co-investigator Urs Staufer of the
University of Neuchatel, Switzerland, who leads a Swiss consortium
that made the microscope.
"Taking this image required the highest resolution microscope
operated off Earth and a specially designed substrate to hold the
Martian dust," said Tom Pike, Phoenix science team member from
Imperial College London. "We always knew it was going to be
technically very challenging to image particles this small."
It took a very long time, roughly a dozen years, to develop the
device that is operating in a polar region on a planet now about
350 million kilometers or 220 million miles away.
The atomic force microscope maps the shape of particles in three
dimensions by scanning them with a sharp tip at the end of a
spring. During the scan, invisibly fine particles are held by a
series of pits etched into a substrate microfabricated from a
silicon wafer. Pike's group at Imperial College produced these
silicon microdiscs.
The atomic force microscope can detail the shapes of particles
as small as about 100 nanometers, about one one-thousandth the
width of a human hair. That is about 100 times greater
magnification than seen with Phoenix's optical microscope, which
made its first images of Martian soil about two months ago. Until
now, Phoenix's optical microscope held the record for producing the
most highly magnified images to come from another planet.
"I'm delighted that this microscope is producing images that
will help us understand Mars at the highest detail ever," Staufer
said. "This is proof of the microscope's potential. We are now
ready to start doing scientific experiments that will add a new
dimension to measurements being made by other Phoenix lander
instruments."
"After this first success, we're now working on building up a
portrait gallery of the dust on Mars," Pike added.
Mars' ultra-fine dust is the medium that actively links gases in
the Martian atmosphere to processes in Martian soil, so it is
critically important to understanding Mars' environment, the
researchers said.
The particle seen in the atomic force microscope image was part
of a sample scooped by the robotic arm from the "Snow White" trench
and delivered to Phoenix's microscope station in early July. The
microscope station includes the optical microscope, the atomic
force microscope and the sample delivery wheel. It is part of a
suite of tools called Phoenix's Microscopy, Electrochemistry and
Conductivity Analyzer.