Atmospheric Entry Heating of Interplanetary Dust

Abstract

The Earth is continually bombarded by interplanetary dust accreting at a rate of about 30,000 tons per year. Although most dust particles larger than about 100 μm in size vaporize on atmospheric entry producing meteors, smaller particles, typically ranging from 5 to 35 μ m in size, radiate heat so efficiently that they decelerate in the upper atmosphere without melting. The peak temperature reached during atmospheric deceleration of an interplanetary dust particle depends on the shape, size, density, entry velocity, entry angle, and radiational properties of the particle. Equations to model the atmospheric entry deceleration and heating of spherical interplanetary dust particles are described, and time-temperature heating profiles from computer simulations are presented. Entry heating modeling shows that most of the interplanetary dust from 5 to 25 μm in size is not heated to its melting temperature, and many particles 10 μm in size are not heated to temperatures at which their chemical composition or mineralogy is altered. Modeling shows that most interplanetary dust particles near 10 μm in diameter accrete onto the Earth with their organic matter intact, and these small interplanetary dust particles could have made a significant contribution to pre-biotic organic matter on Earth. The properties of interplanetary dust particles recovered from the Earth's stratosphere and from the polar ices are in general agreement with the results of the entry heating modeling, confirming the general validity of the model.