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The Phoenix launch. Credits: NASA

The Phoenix spacecraft was successfully launched on the 4th of August 2007.

The Phoenix Mission

Lift-off

The 4th of August 2007 the successful launch of the Phoenix spacecraft set an impressive array of scientific instruments en route to Mars. The spacecraft cruised the interplanetary space between Earth and Mars for 10 months before touching down at the arctic planes of Mars on 25th of May 2008.

Purpose

Scientific evidence indicate that liquid water once covered large areas of Mars, and as water is believed to be one of the main prerequisites for life, the remains of this water is of keen interest to the scientific community.

To investigate the water ice located just centimeters below ground in the circumpolar region of Mars, the Phoenix lander featured a robotic arm capable of digging through the top soil and carrying samples to the lander platform for scientific analysis.

As well as analyzing the ice beneath the soil, the Phoenix lander perform other studies to complement NASA's Mars science goals:

  • Determine whether Life ever arose on Mars (The Phoenix landers will study the habitability potential of Mars, especially focusing on the history of water on mars.)
  • Characterize the Climate of Mars (The Phoenix lander features a meteorological station to examine the weather of Mars.)
  • Characterize the Geology of Mars (As well as a wide assortment of on-board scientific tools to examine the soil, the Phoenix lander also boosts a high resolution stereo imager, capable of sampling through 12 filters to examine wavelengths from the optical to the infrared. When properly calibrated it can be used to examine both airborne dust and rocks and sediments on the surface of Mars.)
  • Prepare for Human Exploration (The Martian ice could become important for future manned missions to Mars. The Phoenix lander is ideally suited to examine the Martian ice and asses the value of the arctic region as a possible area for human occupation.)
The Phoenix lander. Credits: NASA/JPL

The Phoenix lander used its robotic arm to dig through the top soil and reach the ice below.

Design

Despite the success of the airbag landing systems used by Pathfinder and the two Mars Exploration Rovers, the Phoenix lander will use rocket thrusters and legs to touch down softly on the Martian surface. This was a necessary decision because the Phoenix lander at 350 kg is heavier than the Exploration Rovers and Pathfinder.

Since the subsurface ice is believed to ubiquitous in the landing area there is no need for the lander to be mobile. Instead the lander uses a 2.35 m (7.7 ft.) long robotic arm to collect soil and ice for analysis on the main platform.

Payload with Danish contributions

• Surface Stereo Imager (SSI)
The stereo imager is an advanced stereographic panoramic camera mounted on a mast reaching to approximately 2 meters above ground. From this vantage point it can create stereographic color pictures and virtual 3d views of the immediate environment and the lander itself. This will help operators pick good digging locations and control the lander through its expected three month of operation where one-way radio transit times range from around 15 to 20 minutes.

Filter wheel. Credits: NASA/JPL

12 filters of geological and atmospheric interest for each eye allows the SSI to image the optical and infrared region with a wider range of spectral information than any animal on Earth.

The stereo imager will not only serve as the eyes of the Phoenix lander, it will also be used to examine the soil and athmosphere. For that purpose it incorporates 12 different color filters sampling the visual and infrared spectrum.

During its interplanetary cruise and operation period on Mars, the imager is likely to loose accuracy. To combat this problem the imager is periodically calibrated against Caltarget reference targets developed by the Mars/Mössbauer group. These reference targets stay clean by exploiting magnetic properties of the Martian dust discovered using several magnets on Pathfinder and the Mars Exploration Rovers.

• Microscopy, Electrochemistry, and Conductivity Analyzer (MECA)
The MECA is a combination of several instruments, one them being an AFM microscope. This kind of microscope was designed to address a major shortcoming of the scanning tunneling microscope: its inability to picture nonconducting surfaces requiring such samples to be coated with a metal before being examined.

The AFM microscope maps a surface by moving a very sharp tip on a microscopic cantilever in a zig-zag pattern in close proximity to the surface. Atoms in the tip interact with atoms in the surface creating minute forces that bend the cantilever. These deformations are measured by reflecting a laser beam of the top of the cantilever and measuring its deflection. The measurements are used to create a three dimensional map of the surface topography with nanometer resolution, much finer than could ever be achieved with an optical microscope.

The MECA features, among other instruments, an optical microscope, an AFM microscope with 8 disposable tips and a wheel with 69 different substrates to hold samples for the microscopes. This wide variety of substrates ranging from sticky polymers to magnets help scientist discover as many properties of each sample as possible. Mars/Mössbauer has contributed specialized insets to the MECA.

The Phoenix Mars lander in testing