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Magnetic Properties Investigation

NSSDCA ID: 1996-068A-04

Mission Name: Mars Pathfinder
Principal Investigator:Dr. Jens Martin Knudsen

Description

The Mars Pathfinder Magnetic Properties Experiment was designed to study the magnetic composition of the martian dust and soil. The experiment consists of three distinct investigations, each involving the use of magnets which capture wind-blown dust and saltating soil grains containing ferro-magnetic materials. The type of magnetic materials found on Mars can provide information on whether the material was formed in an environment with abundant water or not.

The first investigation, the magnet array experiment, consists of two arrays each containing 5 magnets of varying strengths. As wind blows dust over the array, dust containing ferromagnetic material would stick to the magnets. The Mars Pathfinder camera photographed the magnetic arrays periodically through 9 optical filters and the amount of dust collected as a function of time and magnet strength can be studied. One array is mounted close to the ground so as to capture saltating sand grains, the other mounted higher so as to only attract wind-borne dust. Each magnet array consists of two blocks of magnesium, one block carrying two magnets with average surface magnetic field strengths of 280 and 70 milliTesla (mT) (similar to those used on the Viking Landers), and another block carrying 3 weaker magnets of 49, 23, and 11 milliTesla. The mean surface magnetic field gradients (the attractive magnetic force) of the magnets are, respectively, 130, 45, 21, 11, and 5 Tesla/meter. When mounted the magnets are completely covered by magnesium. Each magnet in the array is an annular ring magnet, 18 mm in diameter, surrounding a central cylindrical magnet, in order to produce a bulls eye pattern of attracted dust.

By observing on which magnets the dust adheres, one is able to deduct some essential magnetic properties of the dust (e.g. the saturation magnetization). The images taken through the 9 optical filters in the visible and near-infrared will allow reflection spectra of the dust to be determined. This data may give information on the identity of the minerals in the dust, in particular those responsible for the magnetization of the martian soil. After 68 sols the images showed clear bulls-eye patterns on the 3 strongest magnets and a discernable pattern on magnet 4. This would indicate ferric oxide, at least some of which is probably maghemite, indicating formation in liquid water. Alternatively the particles could be titanomanetite which would not require water.

The tip plate magnet investigation consists of a single cylindrical Sm-Co magnet embedded in magnesium and situated about 10 cm from the Mars Pathfinder Lander camera eye. The magnet is constructed so that the magnetic field (B) and the magnetic field gradient (NB) varies across the surface of the magnet, the highest strength (B=0.25T, NB=130 T/m) corresponding to the strongest magnet used on the Viking Landers. The outer diameter of the magnet is 18 mm, and the magnet is located about 1.3 m above the surface, where it will attract any wind-borne dust which blows over it through time. The magnet is imaged through the diopter lens of the lander camera with a resolution of about 140 pixels per 18 mm. The high resolution makes it possible to determine if the magnetic grains are aligned in chains or not. A chain structure indicates the grains are primarily single phase magnetic particles with a substantial magnetization. Multiphase particles - or superparamagnetic particles - will generally not form chains.

The lander also carries two ramp magnets, which are attached to the ends of the two rover deployment ramps. The ramp magnets cover a 10 cm by 10 cm area and are made up of magnetic lamellae of a width of 4 mm and a length of 96 mm. The magnetic lamellae are covered with a layer of aluminized mylar, that also covers the voids between the lamellae. When the ramp is deployed each ramp magnet forms a plane magnetized surface at the very end of the ramp next to the surface, where saltating grains and wind blown dust containing ferro-magnetic material will stick to them. After the magnets have had time to collect a sufficient layer of magnetic dust and soil, the Mars Pathfinder Rover was planned to drive up and deploy the Alpha-Proton-X-ray Spectrometer (APXS) to determine the composition of the collected dust, but this procedure was not done before loss of contact. This would have allowed a comparison with the typical dust and soil analyzed on the surface by the APXS, and given information on the type of ferro-magnetic material that exists on Mars.

Alternate Names

  • MPE
  • MarsPathfinder/MPE

Disciplines

  • Planetary Science: Atmospheres
  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Jens Martin KnudsenLead InvestigatorUniversity of Copenhagenknudsen@fys.ku.dk

Selected References

  • Hviid, S. F., et al., Magnetic properties experiments on the Mars Pathfinder Lander: Preliminary results, Science, 278, No. 5344, 1768-1770, doi:10.1126/science.278.5344.1768, Dec. 1997.
  • Gunnlaugsson, H. P., et al., Instruments for the Magnetic Properties Experiments on Mars Pathfinder, Planet. Space Sci., 46, No. 4, 449-459, doi:10.1016/S0032-0633(97)00199-2, 1998.
  • Madsen, M. B., et al., The magnetic properties experiments on Mars Pathfinder, J. Geophys. Res., 104, No. E4, 8761-8779, doi:10.1029/1998JE900006, Apr. 1999.
  • Hargraves, R. B., et al., Magnetic enhancement on the surface of Mars?, J. Geophys. Res., 105, No. E1, 1819-1827, doi:10.1029/1999JE001032, Jan. 2000.
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