An assessment of the meteoritic contribution to the Martian soil.

The addition of meteoritic material to the Mars soils should perturb their chemical compositions, as has been detected for soils on the Moon and sediments on Earth. Using the measured mass influx at Earth and estimates of the Mars/Earth flux ratio, the authors estimate the continuous, planet-wide meteoritic mass influx on Mars to be between 2700 and 59,000 t/yr. If distributed uniformly into a soil with a mean planetary production rate of 1 m/b.y., consistent with radar estimates of the soil depth overlaying a bouldered terrain in the Tharsis region (Christensen, 1986), the authors' estimated mass influx would produce a meteoritic concentration in the Mars soil ranging from 2 to 29% by mass. Analysis of the Viking X-ray fluorescence data indicates that the Mars soil composition is inconsistent with typical basaltic rock fragments but can be fit by a mixture of 60% basaltic rock fragments and 40% meteoritic material (Clark and Baird, 1979). The meteoritic influx the authors calculate is sufficient to provide most or all of the material required by the Clark and Baird (1979) model. The authors also calculate that a significant fraction of particles throughout the 60-1200 μm diameter range will survive Mars atmospheric entry unmelted. Thus returned Mars soils may offer a resource for sampling micrometeorites in a size range which is not collectable in unaltered form at Earth.